Peter FallPeter Fall

Articles

Don’t just block off the chimney breast

Published 25th August 2012

I’d hate to count how many times I’ve written about dampness over the last ten years or so. Rising damp from the ground, falling damp through the roof, damp penetrating horizontally through a wall and even the dreaded condensation damp caused by the unseen source which is most typically you the occupier!

The other day however we were asked to comment on dampness that had started to occur near to ground floor level, on a chimney breast in the middle of a house. The house was a fairly typical 1950’s semi with two reception rooms, both of which had chimney breasts blocked off for many years before the clients bought the house. The clients first noticed the damp patch a couple of weeks ago.

The chimney stack that served the fireplace was a combined one in the centre of the ridge with four chimney pots, two for each of the semi’s. All the chimney pots were still in place and three of them had cowls over but not the one serving this fireplace. Also, the pointing around the pots was breaking away. The pointing to the brickwork of the stack wasn’t good but I’ve seen worse, a lot worse in fact.

To understand what is going on here you have to understand a bit of construction theory. When the house was built, the fireplace at ground floor level would have a flue not just going upwards but leaning over towards the centre of the house. It would do this leaning over in two bites, one at ground floor level within the wide chimney breast and another at attic level. At first floor level it would go straight up. During the 1950’s they started to line flues with round clay pipes rather than the traditional method of a square brick box lined out in mortar applied in a curve to get rid of the square corners. The round clay pipes reduced the soot build up and let the smoke flow faster and more efficiently up the chimney Accessories.

The chimney was intended to be in regular use therefore the possibility of rain soaking into the stack at high level was never a problem with hot smoke flowing up the flue drying out any damp brickwork. Even in summer warm air ventilating out of the living room went up the chimney to the outside. But that isn’t the case now.

When this fireplace was removed and the opening bricked up, the owners failed to incorporate an air vent in the new wall. Presumably they thought leaving the chimney open at the top would be sufficient to keep the flue dry. Unfortunately it isn’t.

The problem here is a combination of factors, all exacerbated by the lack of the air brick at the bottom of the old flue.

The dampness hadn’t been known to happen before, probably because the house hadn’t been subjected to such a prolonged period of regular rainfall as it did from April to July this year. On top of that, just when the brickwork to the chimney was well and truly saturated along came ‘storm Thursday’ and shortly after, the heavy rains of early August. These heavy downpours simply went straight through the brickwork and into the flue. The clay pipes of the flue, being nice and shiny, let the water trickle down the inside right to ground floor level where it dripped onto the old concrete hearth. From here it soaked into the side walls of the chimney breast and bingo, apparent rising damp.

Possibly if the chimney pot had a cowl then less water would have entered the flue. Also if the pointing on top of the stack and the pointing in the mortar joints had been sound then less water would have soaked in over the four month period. But for me the critical factor was the missing air brick at the bottom. Had warm dry air been constantly flowing from the downstairs room up the stack it would have evaporated some of the rainwater penetration and I don’t think the damp would have been seen.

Ah well, they’ve got an air brick now.


324 Response to 'Don’t just block off the chimney breast'

  • Paul rowan

    Would an external vent be sufficient in a detached house? We are about to brick up an unused fireplace with an external chimney and would like to not have an airbrick showing in the room.

    Thursday, January 17th

  • peterfall

    The benefit of the internal airbrick is the warm air from inside the house helps to dry out the flue. Whilst an external air brick will still get air to flow up the flue, at times of cold and wet weather the drying effect will be much reduced. A further benefit of the internal airbrick is it gives natural ventilation to the room.
    The airbrick inside the room can be coverred with a plaster louvre vent to improve the appearance but I agree it doesn’t look good.

    Thursday, January 17th

  • Simon Coulter

    We are currently buying a house. It has had it’s chimneys blocked off at the breast, an air brick is in place and their is a patch of damp showing approximately a foot in diameter and a foot from the ground, exactly where the old fire place used to be. The chimney pot is not blocked. What would be the best solution?

    Wednesday, June 12th

  • peterfall

    Diagnosing damp without seeing it and its situation is fraught with problems so I will resist a specific comment.
    One difficulty with old fireplaces is soot contains salts that absorb humidity in the atmosphere so if a soot fall has occurred behind the bricked up opening then the salts can migrate through the wall and into the plaster. It may be that this has happened and the damp patch is salt contamination that is absorbing moisture from the atmosphere in your room. Have the plaster tested for salts and if this is the case re-plaster with a salt resisting plaster.
    If the fireplace is at ground floor level then rising damp can soak up from the ground and through the old hearth. This could be the cause.

    Wednesday, June 12th

  • Steve Callaghan

    Hi Peter
    I read your article and replies with interest. we have penetrating damp with salt crystals and black mould on the plaster of an upstairs bedroom chimney breast (the chimney breast is external to the house and the prevailing rains hit it). Judging by the stains on the plaster this has been a problem over many years (this was originally vented top and bottom but vent covered with an electric fire downstairs restricting the flow of air). Since then we have fitted a woodburner stove with a stainless steel flue liner – so effectively the inside of the brick chimney flue is sealed with no air flow but the same problem of damp and even one occasion of water trickling out of the middle of the breast (note – our roof and leads etc are all sound and have been inspected by 2 different companies).

    I read with interest your reply above to Paul Rowan regarding an external vent. although we have a different scenario would 2 external air vents (one top and one bottom) create enough air flow to prevent condensation building up and therefore penetrating damp in the bedroom. we have considered internal air vents (bedroom and above the woodburner downstairs) but I have a concern regarding any future potential CO leaks from the stainless liner.

    thank you in advance for any advice
    regards
    Steve Callaghan

    Saturday, July 13th

  • peterfall

    Steve
    The addition of an air brick at the top and bottom of the flue will certainly reduce condensation but I suspect your problem is more from penetrating damp than condensation if you have water trickling out from the middle of the flue. By all means try the airbricks they can only do good but you may then have to address the problem of damp from the prevailing winds penetrating the outer stack and soaking through to the inner.
    Peter Fall

    Monday, July 15th

  • David Priest

    Hi Peter,
    I have just seen this article and it’s just what I was looking for. I moved into a first floor flat last year and discovered a damp patch in the plaster above the fireplace. The previous owners installed an electric fire into the old fireplace and as far as I can tell haven’t installed an air brick. The flat is a converted 1900s house and everything else (roof, flashing etc) seems to be fine. My plan was to put an air brick just above the mantelpiece and re-plaster the wall above the fireplace. Do you think that this is sufficient or should I do anything else? Also, is there anything else I need to think about before doing the work?
    Thank you in advance,
    David Priest

    Tuesday, July 16th

  • peterfall

    David
    Regrettably it is very difficult for me to give advice without seeing both the problem and the building itself. If the staining is from the flue salts you will need to first remove the affected plaster, then treat the exposed brickwork and in particular the mortar joints with a sulphate resistant primer before re-plastering with a sulphate resisting cement render finished with gypsum plaster. The addition of the airbrick will help but unfortunately if the salts have migrated through the wall they won’t now migrate back into the flue.
    Peter Fall

    Monday, July 29th

  • Steve Callaghan

    Hi Peter
    Thank you so much for your advice. I guess we can use a water repellent such as a silicon external waterproofer as a starter for ten. Do these products let the bricks breathe?
    Thanks again
    Steve

    Wednesday, July 17th

  • peterfall

    Steve
    I’m afraid I have little time for the silicon waterproofing materials. Whilst they will seal the bricks they don’t let them breathe and because they are colourless you can’t see how much you have applied so it can be a patchy finish where the weak areas still let water in but the strong areas prevent it from evaporating out.
    Peter Fall

    Monday, July 29th

  • Steve Callaghan

    Thanks Peter for your time, advice and professional judgement
    Kind regards
    Steve

    Monday, July 29th

  • Tim

    Hi Peter,
    Thanks for this article – it is very informative. I am currently bricking up a fireplace and I intend to put an electric fire on the wall in its place. I see this done very often but was wondering what to do about ventilation? I am guessing that a new fire would either restrict or totally bock any air flow from the air brick in the standard position. I have asked quite a few people but nobody can give me an answer, it’s as if nobody has ever come across the problem before. Thanks if you can help.

    Tuesday, July 30th

  • peterfall

    Tim
    You should be able to incorporate air vents beneath above or even at the sides of the fire in positions that are not too conspicuous.
    Peter Fall

    Thursday, August 1st

  • Gwyneth Page

    Wow Peter, I think I am finally on to something with regards to the mystery of the damp patches on my son’s bedroom wall thanks to your postings!
    There is an open fireplace in his room, unused but swept with an elephant foot chimney cover, however there is a second chimney pot on the stack which leads down to room beneath where the fireplace has been plastered over and there is no ventilation. This is also covered by elephant foot.
    The patches upstairs get significantly worse during winter months. There are also rising damp patches on the downstairs chimney breast and surrounding alcove walls.
    The house was built around 1815 and we have been throwing money at this problem for 3 years now with no resolution. Chimney stack is in good repair, pointed and pots sealed. loft space/roof has had ventilating tiles added and the loft space is now bone dry. Have been using a dehumidifier in the room to try and keep it under control.
    We are now considering opening up the downstairs fireplace, sweeping out chimney (as likely to be old nests – we live in jackdaw central) and putting in a stove. Would this help do you think? I presume we would also need to replaster given other advice on this thread.
    I am despairing with this!
    Hopefully
    Gwyneth

    Monday, September 23rd

  • peterfall

    It’s very difficult to give good advice when I haven’t seen the house, how it is built, its exposure to the elements and the problem, so any comment I make is only general I’m afraid.
    Salts embedded in the stack will cause staining at high level on the stack. On large roofs with the stack at the ridge the staining occurs in the roof space. Where the roof is very shallow or the stack is at the eaves then the staining can extend down to the ceiling of the room beneath. To overcome it you need to remove the affected plaster, seal the wall with sulphate resisting primer and the apply a sulphate resisting render to the wall, finishing with plaster.
    Ventilating the flue will prevent the salts from migrating to the face of the stack but once they are embedded no amount of ventilation to then flue will remove them.
    Peter Fall

    Monday, September 30th

  • anne

    Hi
    We’re steadily improving the energy efficiency of our victorian terrace, and reducing draights has had a brilliant effect. One recent job was to seal the gaping holes in the unused fireplaces. The chimneys are properly capped with big terracotta caps, but theres now no vent into the room. I don’t want to waste more of our heat energy than necessary in keeping the chimney dry, but equally I don’t want to get damp building up, so my question is “how small a vent can one get away with?” I was wondering if one could use a thin plastic pipe down the back of the fireplace to pull air from the unheated void below the floorboards. Any suggestions about how to be both damp free and energy efficient?

    Thursday, October 3rd

  • peterfall

    Anne
    The main thing is to keep the inside of the flue dry so that any damp doesn’t migrate to the outside of the chimney breast. I can’t say what is the minimum size but the normal is a 225×225 air vent. I can’t see the thin pipe idea working.
    You say there is no ventilation in the room. This is not good for you or the room. You must maintain a flow of fresh air through the room to get rid of the humidity you will generate by normal living. The vent through the flue will help with this providing you also have a fresh air inlet into the room.
    Peter Fall

    Friday, October 4th

  • Liz

    Hi Peter,

    I bought my house 10 years ago and since then a mystery damp patch has appeared and steadily got worse in my living room. The house was built around 1900 and was originally a two-up two-down stone end of terrace. The current living room is in the original stone part of the house. The house now has a breeze block extension to the side and rear (>25yrs old). The wall with the problem was originally the external wall to the propertty (and is now an internal wall between living room and kitchen). It is apparent that the wall originally had a fireplace in it because there are cracks in the plaster which clearly take the shape of a fireplace and flue. There is no vent. The damp comes and goes. It does not appear to directly coincide with rainy weather. The damp is located between 1.5 and 1.9 metres above ground level , at either side of the original flue.
    Upstairs the original stone wall has been taken away (including chimney breast) and the room layout has been reconfigured with stud walls….so it is not possible for rain to be coming down a chimney. The roof is in good condition and the roof space is dry. Our bathroom is downstairs so there is no water coming e.g. from a leaking shower. We do have a water pipe which travels through the ceiling to transfer water from the bathroom to the kitchen. I’m not sure if it goes directly over this affected area but I can’t see that this would be leaking otherwise the damp would be there all the time.
    For a long time I assumed it was rising damp but I’ve recently been told that rising damp doesn’t reach such heights and there is no issue lower to the ground.
    The damp dissappeared this summer and it had been very dry for months. However, this week (warm and humid aswell as wet) it is extremely bad. I’m wondering if the soot salts may be the issue? Your thoughts would be very much appreciated.

    Thanks
    Liz

    Friday, October 4th

  • peterfall

    Liz
    Obviously I can’t be definite about your particular problem without seeing the defect and the house itself but salts from chimneys are hydroscopic so they will absorb moisture from the atmosphere particularly when it is humid. The answer to the salts is to remove the plaster, treat the wall behind with sulphate resisting primer and then re-plaster with a sulphate resisting plaster. Don’t be restrictive on the area you treat as the salts may have spread further than is at first apparent.
    Peter Fall

    Friday, October 4th

  • victor gibson

    when I fit the vent to a bricked up fire place do I have to remove a brick or can I drill a number of large holes through the bricks then fit the vent many thanks

    Friday, October 11th

  • peterfall

    The main thing is to get as much warm air as possible up the chimney. A few holes will not be enough. Go for removing a couple of bricks and a 225×225 air vent. The vent is more than enough restriction to the flow of air.
    Peter Fall

    Friday, October 11th

  • Maria Vaquera

    Dear Peter,

    I hope you can put some light on my way.

    After about seven years of throwing money away on different roofers’ guessing games as to what might be the cause of a damp patch that appears in the inside wall of the downstairs room, I have decided to search the net before I throw myself off the chimney stack in desperation. It has been by pure luck that I have come to your page / forum.

    I have read with great interest all the comments posted and your replies. I am not sure they relate to me in my case, but I have no knowledge to say that categorically.

    I live in an end of terrace house. About 6 or 7 years ago I started to notice a patch of water on the outside wall of the house, horizontally, parallel to the floor, at about one meter from the ground and the damp course. That happened in just one area and over the years it has extended to cover the whole length of the house, horizontally and, where this particular offending chimney is, it started to go upwards too, towards its stack, but never higher than what it would be the upstairs floor. The mark outside the house is always visible and it accentuates when there is even a bit of fog or more moisture than usual in the air. If it rains it starts to show in the interior wall of the chimney breast. There are no marks in the inside walls of the room or in either sides of the chimney breast.

    I have had new flashing, new tiles around the chimney stack; last year I had yet again a new flashing put as allegedly the one that was put a couple of years earlier was not done properly. It has been capped too, with air bricks at the top to allow air flow. Although everyone said the dam proof membrane was ok, I had the wall infected last year too – just in case!
    There used to be a gas heater mounted to the chimney but it was removed and covered but it has air ventilation.

    It has rained during the last two days and the damp patches now cover most of the inside breast. I went up yo the loft myself today to do some research and all is bone dry. I am in total desperation now.
    Either I throw myself off the chimney stack as I said, or I sell the house if I don’t solve this problem – or mystery! Rather. I could get more and more and more people to look at it again just to spend money on “it may be”, “perhaps it will cure it”, “there might be”…….. Enough of guessing games. Can you please help me? What do you think it might be the cause of my sleepless nights when it rains?

    Many thanks for reading this long post and for your reply in anticipation.

    Maria

    Saturday, October 12th

  • peterfall

    Maria
    Unfortunately I cannot advise on your specific problem as I haven’t seen the problem or the building. I can say however that chemicals from rising damp or soot deposits in flues can migrate and lodge in the face of a wall. These are hygroscopic absorbing moisture from the atmosphere giving manifestations of damp at times of high humidity such as rainy days.
    I suggest you contact a local building surveyor that specialises in building problem diagnosis and request an investigation that would include an analysis of the plaster for these chemicals.
    Peter Fall

    Thursday, October 31st

  • Charlie

    But what of interstitial condensation?

    I have an old sandstone house with a capped fireplace that I want to block up. I intend to dryline the walls and apply insulation and plaster board over a cavity. I was planning to apply this structure over the old fireplace as well. Normally with a wall construction like this it would be neccesary to seal everything to prevent warm air from the room from condensing behind the insulation. Venting the fireplace will surely undo all this good work.

    Should I be sealing the fireplace opening around the cavity and venting the fireplace internally or is it enough to allow the airflow in the cavity to dry out any penetrating dampness?

    Monday, October 14th

  • peterfall

    Charlie
    The ventilation is to keep the flue way dry and prevent the salts migrating from the damp flue to the dry outer faces.
    If you dry line and keep the plaster off the face of the chimney breast the salts will stay in the chimney breast and not appear as damp patches on the wall.
    Peter Fall

    Thursday, October 31st

  • vic gibson

    hi peter I intend to remove a couple of bricks from my ground floor mantle breast and fit a vent. how high from the skirting board should this be

    Wednesday, October 16th

  • peterfall

    Vic
    Any height is acceptable but I suggest 300-600mm below floor level.
    Peter Fall

    Thursday, October 31st

  • vic gibson

    hi peter when I removed 2 bricks from the ground floor mantle breast I saw what seemed to be a 1940s/50s back boiler.it would have to be the first one installed I intend to follow your advice on remove plaster prime brick work .render finishing coat ,all materials sulphur resisting

    Friday, October 18th

  • Peter Jacob

    Dear Peter
    We are getting rid of a gas fire and repacing it with an eletric one. The house is 6 years old.
    The electric fire manufacturers have suggested putting rock wool into the chimney to address the problem of cold draughts affecting the new fire’s thermostat. After reading all your comments on your web site I am very dubious about taking their advice.
    I am also concerned about the heat loss, if I leave the chimney open.
    The chimney has a ‘Gas End’ on it (I use the words the builders used)
    I would be grateful gor your comments please
    Peter

    Saturday, October 19th

  • peterfall

    Peter
    If the flue is only 6years old it will not have a problem of salts in the flue so the ventilation isn’t required. Go ahead with the insulation.
    Peter Fall

    Thursday, October 31st

  • Peter Jacob

    Dear Peter
    We are getting rid of a gas fire and repacing it with an eletric one. The house is 6 years old.
    The electric fire manufacturers have suggested putting rock wool into the chimney to address the problem of cold draughts affecting the new fire’s thermostat. After reading all your comments on your web site I am very dubious about taking their advice.
    I am also concerned about the heat loss, if I leave the chimney open.
    The chimney has a ‘Gas End’ on it (I use the words the builders used)
    I would be grateful for your comments please
    Peter

    Saturday, October 19th

  • Stevo

    We have a chimney in a rear bedroom which has been blocked by previous owners in the bedroom and also the stack has been removed to beneath the roof. The remaining chimney has been covered I think in the roof and we are now experiencing a lot of surface damp on the walls of the chimney. Can you give me any advice.

    Saturday, October 19th

  • peterfall

    Stevo
    I can’t advise on your specific problem as I’ve not seen it or your building. It does sound like salt impregnation from the old flue. The salts need to be removed by removing and replacing the plaster if this is the cause.
    Peter Fall

    Thursday, October 31st

  • Sarah Groom

    We have just brought a 1894 end terrace. The fire place in the living room is open and in working order. But the fire place in the dining room is blocked. It’s vented but not capped. Before we moved in the surveyor found damp so the vendor had it re plastered and we thought that was the end of it. This week I painted the fire place and noticed now that there is a damp patch forming at the bottom corner (a place he did not re plaster) The man treating the damp said it was just cheap plaster but I’m not sure. This week we have had really heavy rain and I don’t know if its the rain coming down the chimney and getting soaked in to the brick or rising damp.
    Many thanks,

    Monday, October 21st

  • peterfall

    Sarah
    I’m afraid I can’t comment on this without seeing it and plotting the dampness pattern. If you are within a 30mile radius of Newcastle upon Tyne give me a call and I can quote a fee for a survey.
    Peter Fall

    Thursday, October 31st

  • Peter Jacob

    Peter
    Further to my question dated Saturday 19th, If I use a 100ml pipe from the bottom of the chimney to a standard vent, would that, in your opinion, be ok?
    Regards
    Peter

    Monday, October 21st

  • Chris

    Hi Peter
    I’m also currently suffering from a damp patch on my joining wall to next door, when I bought the house it was already precent and the previous owner has removed the chimney breast, I have put a small vent in the dot and dab wall which is roughly the size of a letter box, and the pots on the roof have a a cap on them with holes around the sides, I’ve had a roofer out to check all the roof,lead and chimney stack which he said is all ok, it does seem to get worse in the winter with the rain etc, I’m thinking of tacking the plaster board off and seeing what he has covered over if anything, could you please give me any guidance thanks

    Monday, October 21st

  • peterfall

    Chris
    I’m sorry I can’t comment on this without seeing the problem and the construction of the building.
    Peter Fall

    Thursday, October 31st

  • Denis

    My problem arises from an old flue that would at one time served some type of solid fuel stove in the kitchen. Within the kitchen the flue has two sealed inspection plates but the ‘open end’ was presumably bricked-up when the stove was removed. Since the spell of wet weather I have noticed a growing patch of damp plaster above a doorway in the hall. Opening up one of the inspection plates in the flue revealed that it changes direction from an incline of approximately 45 degrees to vertical at the point where the damp has occurred. The chimney pot is covered with what I assume to be a half-round tile, which allows drafts down the flue but not rain. Any advice would be welcome.

    Wednesday, October 23rd

  • peterfall

    Dennis
    I’m sorry but I can’t comment on this without seeing the problem and the construction of the building.
    Peter Fall

    Thursday, October 31st

  • Joe

    Peter, with the rising cost of fuel ie gas electric is it worth considering opening up the fireplaces in all the rooms including the bderooms and going back to open solid smokless fuel fires???

    we have external chimney breasts so i am wondering if most of the heat would go outside????

    i am guessing internal chimney breasts running through the centret of the house are more efficent but unfortunately ours are external

    Thursday, October 24th

  • peterfall

    Joe
    The heat loss up an open fireplace is horrendous. The open fire is the least efficient method of heating a room.
    Peter Fall

    Thursday, October 31st

  • Andy Cotton

    Peter,
    I have recently removed an old gas fireplace and back boiler from my chimney breast. What is have left is a 2×2 foot hole and a aluminium flue going to the chimney pot (I assume).
    I have Purchased a electric fire with wooden surround (freestanding), my intention is to simply surround the hole with the fireplace. This will leave a 1cm gap between fireplace surround and wall, will this gap be sufficient for airflow to prevent any possibilty of damp or would you suggest trying something different?
    Regards,
    Andy

    Thursday, October 24th

  • peterfall

    Andy
    I presume the gap is 1cm wide and 8ft long (2x2ft). This is a good air gap for ventilation.
    Peter

    Friday, November 8th

  • Alison Thomas

    Hi Peter,

    I have exactly the same problem as Steve, having installed a wood burner and blocked up the opening behind it. Our chimney is external to the house and the brickwork at the top of the chimney breast is in bad condition, on top of this cavity wall insulation was put in before we bought the property! We have recently started having damp patches on the walls and were hoping to sit tight until he spring and then fix the brickwork, any advice?

    Would plastering the external chimney breast fix it?

    Thanks
    Alison

    Sunday, October 27th

  • peterfall

    Alison
    I really can’t say I’m afraid without seeing the house, how it is constructed and where and how extensive the damp patches are.
    With or without damp it is good husbandry to repair the chimney stack.
    Peter

    Friday, November 8th

  • Jonathan Stephen Lane

    Hi Peter. Excellent advice!We have been having problems with black mould coming through our bedroom wall behind my wardrobe(outside weather facing wall) and light coloured mould behind the bed where the chimney crosses to the middle of the house. We have an open fireplace downstairs but we removed the chimney top and replaced with tiles because of the condition of the chimney. Would putting a high level external airbrick help? If we installed a fire with flue exiting at high level would this dry the walls? The areas affected are covered in mould but do not seem to be wet. The house was built around 1900 and we have just installed extractor fans in the bathrooms and kitchen. Any advice you can provide would be much appreciated.

    Tuesday, October 29th

  • peterfall

    Jonathan
    The black mould could be condensation in the room as a result of the way you occupy the house. Before you start to blame the chimney you need to consider how much humidity you generate from cooking, washing, drying clothes and bathing, how you remove that at source rather than let it dissipate inside the house, the level of heating you have in the affected room and the level of thermal insulation and porosity of the external walls. Too many factors to diagnose the cause of your mould growth on a web site I’m afraid.
    Peter

    Friday, November 8th

  • Trish

    Hi Peter
    I bought a bungalow 5 years ago and noticed that the wall above the chimney breast (slightly to the side) was damp. The whole place was taken back to the brick and re plastered so at the same time the builder added some damp course material at that level. A whole new chimney was put in outside and a new roof but still this damp patch continues to come and go with the rain! The damp seems to work its way around the damp proofing and shows about one third of the way down the wall.
    just about to install a wider umbrella shaped chimney pot to stop any water getting in there but basically at a loss as to know what to do next. Any ideas?
    Trish

    Tuesday, October 29th

  • peterfall

    Trish
    If you are satisfied that your builder has taken measures to prevent damp coming in from outside then it could be contamination in the plaster. Salts from soot deposits on the inside of a flue will migrate to the faces of the chimney stack and lodge in the plaster and bricks. These salts are hydroscopic so they absorb moisture from the atmosphere, particularly at times of high humidity. (eg raining) Simply replacing the plaster with new will only provide a short term remedy as the salts left in the bricks then migrate into the new plaster. The re-plastering should include a sulphate resisting primer on the bricks and a sulphate resisting plaster to hold the salts back inside the brickwork.
    Peter

    Friday, November 8th

  • Ian Turner

    Hi Peter

    I have a period Victorian property with 7 open fires, they are all fully open and as you can imagine the house can be expensive to heat in th winter.

    Ive read through your points on blocking the chimney but would like to ask what can i do to stop the drafts and thus keep my home warm as it can get very cold even with an A+ boiler and both underfloor and attic insulation.

    I should mention i’ve been looking along the lines of, external insulation on the gable end in a few years time and chimney balloons as a short term fix.

    Look forward to your ideas

    Thursday, October 31st

  • peterfall

    Ian
    Old Victorian houses leak air in from the outside by many routes. Look hard at your windows and doors (including letterboxes). Exposed wooden floorboards allow cold air from the subfloor to leak in through the joints but don’t block off the airbricks. Check on holes where waste pipes pass through the wall. Don’t try to make the house airtight, you need air to healthily live. Air won’t come in through the chimney but they will let it out. Stop off the inlets and the amount leaking out will be much less.
    Once you’ve addressed the ‘air leaks’ you will need to look at the thermal insulation qualities of the roof, walls and windows. The walls can be very difficult to treat in your type of property so address the roof and windows first.
    Peter

    Friday, November 8th

  • Gwyneth

    We have opened up the fireplace on the ground floor and today, the chimney sweep removed three large sacks of soot and a large birds nest which have been sealed inside for over 20 years!
    I am hopeful that we have now removed the original source of the problem. I now intend to put the dehumidifier in my son’s room to try and dry out the wall and then see what happens next time it rains…
    From what you have said on this forum Peter, am I right in understanding that we are likely to continue to see damp patches due to the migration of salts – even though the cause is removed? and that is only fully resolved once the plaster is removed and walls treated as you have described earlier. (We have lath & plaster in that room).

    Monday, November 4th

  • peterfall

    Gwyneth
    That’s correct.
    Peter

    Friday, November 8th

  • James

    Hi Peter,

    I simply have a nice fireplace we are keeping that previously had a back boiler now removed. The flue liner is still within the chimney breast and made in at the top. we want to keep it simply as an ornate fireplace but close the underside of the opening to keep the heat in.

    I was thinking what would be the best material, i am just going to batten it out and screw mdf with a vent cut into it.

    In regards to the flue line i was just going to cut it further up and leave this open to vent.

    does this all sound ok to you?

    Thanks In advance!

    Wednesday, November 6th

  • peterfall

    James
    Without seeing the house and the fireplace I can’t confirm with any certainty but what you propose sounds good to me.
    Peter

    Friday, November 8th

  • dominic

    hi Peter ,
    i brought a victorian end of terrace a couple years ago , the previous owners had taken the chimney out from the dining area and what is now my 1 year old’s room so to make to rooms bigger by plaserboarding the walls flat, there are now vents and the chimney is capped off and supported up in the roof space , we have damp appearing in both rooms where the chimney once was , should i put an internal vent in both rooms still ? the house does have double glazing but is old and my little ones room does get cold as there are two external walls . or will a external vent on both the ground and first floor stop this mould ?

    Wednesday, November 13th

  • peterfall

    I can’t really give specific advice without inspecting the problem but I suspect that the vents are not the answer.

    Friday, November 15th

  • Raymond Ross

    hi peterfall I have a 2 storey late victorian house. I removed gas fire mounted on the front of the chimney breast, open up the fire place, to install a miultifuel stove. Sweep has been cleaned and inspected chimney and is in good condition. I have been reminded by my wife that there is an air brick in the side of the chimney breast in the bedroom above. Do I block this off or is it needed for airflow?

    Wednesday, November 20th

  • peterfall

    The flue from the bedroom fireplace should not connect to the other flue so there the flue gasses from the multi-fuel stove should not escape out of the bedroom airbrick. However its not unusual for the brickwork between flues in old properties to break down and allow flue gasses to leak from one flue into another. Your multi-fuel stove installer should check the integrity of the flue you intend to use before installing.
    Peter Fall

    Friday, November 22nd

  • Stephen Jones

    Hi Peter,

    Very interesting reading, I am looking to block up my fireplace, the Flue itself is asbestos and runs up the house inside the cavity wall, with wider Chimney style brickwork externally to accommodate it.

    Does this style of Flue still need to be ventilated via an air brick , if so could it be external , the house is detached and was built in the late 70`s

    Thanks

    Wednesday, December 11th

  • peterfall

    Stephen
    Are you certain the flue is lined with asbestos? or do you mean asbestos cement preformed into tubes and jointed with spigot and socket joints. If its the latter then I don’t think you need the ventilate the flue as the asbestos cement tubes will contain any contamination.
    Peter Fall

    Friday, December 13th

  • terence johnson

    I have a 3 storey edwardian house, with all fireplaces covered up. 20 years or so ago (after buying), on surveyor’s advice, I cut holes in each one, cleared out all the debris and introduce a vent. Have never had any problems with damp since. More recently, I have been spending some time on in the spare room on the 2nd floor and noticed that when the wind is blowing there is a terrific cold draught through the (9″ x 9″ plastic) vent and am wondering what this does for my heating bills.

    So is there some material I can put in the void, or some kind of baffling to put behind the vent, which will maintain airflow (at a reduced rate) and hence reduce the heat loss.

    Friday, December 20th

  • James Labouchere

    Hi Peter – fascinating reading, thank you for your very generous service!
    We have done up a 200 year-old 2-ft solid-stone-walled house in Wales as our home and to do B&B and home office (thus occupied all the time) but we are struggling with a fine mould that develops in chests of drawers, on stored clothes etc. if left unused for any time. Chimney’s are vented etc. Single woodburner is heating air which flows upstairs. Attic is dry and clean. There is much condensations on walls and windows upstairs. I just can not work out a strategy allowing us to keep warm, other than running a condenser all the time, which is a frightful energy burner. Is there a strategy or a check list anywhere, please?
    Thanks in anticipation.
    James

    Friday, December 27th

  • John Dillon

    I would like to block my chimney with a venting cowl, chimney balloon and fire board. I will leave the existing fire in place but unused. Do you think there will be enough ventilation or will we need an external vent for the chimney in the outside wall. It is a Victorian stone built house. Thanks. John

    Wednesday, January 8th

  • peterfall

    Providing you are still allowing air in at the bottom of the flue then this should be ok. It doesn’t need a vast flow of air up the chimney, just enough to keep it dry
    Peter Fall

    Thursday, January 9th

  • Karen Roskams

    Hi peter,
    I have recently bought 1894 partly renovated end terrace, on starting to insulate the roof space the gable walls developed dark staining after prolonged bad weather although a rear chimney has been sealed & capped so my new boiler has an outside vent pipe rather than using that chimney. Then a surveyor from my insurance came out & said the gable walls dampness was an old problem as there was no daylight showing from top of chimney & the 2 metal air vent covers when opened & looked down just showed soot build up below where flues used to go to fireplaces long since unused & closed off by new walls in the 2 lower floors. I ran a dehumidifier in the attic for a month emptying a bucket of water a day over 4 wks.
    i intend to close off the loft ladder and extend the staircase up to the attic so i can use it as gym/hobby room as well as for storage i will also put in a window each side of the roof but as the staining is also evident down the outside of the end wall (once the surveyor points out what to look for) and the neighbours on the party wall side say they have no dampness on their side as the chimney has long since been removed from the middle of the houses. i haven’t noticed any air vents anywhere in the house; please can you advise me on the way forward as i cannot not continue with the intended improvements until i solve the problem?

    Thursday, January 16th

  • peterfall

    I’m afraid I can’t advise you on your problem without seeing the staining, the construction of the house and its exposure to the weather. I can say that soot deposits migrate through the bricks and mortar of a chimney breast and show on the outer faces of the flues. These salts absorb moisture from the atmosphere and will seem to be damp. The problem tends to be worse at the top of a flue rather than at lower levels. It is very difficult to treat these salts.
    Peter Fall

    Thursday, January 16th

  • craig walton roofer

    Hi peter great article im always coming across these venting problems and they are always blocked up stacks I always get them to get the stacks vented problem solved .along with good pointing to the stacks and a top flaunch thanks craig

    Monday, January 20th

  • Cheryl robson

    Hi I have a question about chimneys we have one but it’s blocked off now when a chimney has been capped should I get gusts of wind comeing threw my air vents. As my bed is right next to mine in my bedroom all I can here is the wind comeing threw it does this mean the shimmery isn’t actually capped ? And also down stairs when we first moved in and still now have had to deal with damp paint peeling of the walls and efflorescence from the player I papered over the walls as it was so depressing to look at the land lord had a quick fix damp corse done cheaply and they guys that came just took off my skirting a and drilled holes into old brick which are not like the brick most houses are built with today so I couldn’t see it working and oh shock it hasn’t I still have riseing damp on most walls in the house even on the walls on the inside of the house but the on was wondering if the chimney was actually capped due to all the wind that I can hear I would really like to hear what your reply would be as I have been fobbed off quite a lot told that it’s condensation due to the house being to cold ect

    Saturday, February 1st

  • peterfall

    Cheryl
    I’m sorry but I’m afraid I can’t help to much on this without seeing the building and the dampness. If you are suffering from wind blowing down the chimney this is called down draft and you can get a special cowl to fit on top of the chimney pot to prevent it.
    Peter Fall

    Wednesday, February 5th

  • Karen Roskams

    hello again [from16 Jan]
    i have had a builder in to remove both chimneys to below the roof line, one is in the middle of the gable end he has filled the double flue with rubble from the chimney to enable him to brick up the 2 flues making the wall double brick instead of single & totally flush all the way across that outside end & re pointed the rest of the wall. The other chimney was on the corner of the house he has taken that back to the roof line as it was leaning & recapped it this had already been filled with insulation pearls? [checked it isn’t used for my new gas boiler or oven extractor]. My first question is should he have used some form of pearls – then bricked up the attic flues/will i encounter damp problems or should that be the end of it now?
    This same builder has also pointed out that i need 2 lintels installing over the back yard windows where the fan brickwork has cracked mortar/failed due to the building settling? which is not the same as subsidence?
    I am also keen to make my home as energy efficient as possible and have noticed in your earlier comments about addressing the attic roof windows etc first well i have double glazing the roof is being insulated i have roller shutters on the front of the house windows but am concerned about the lack of vents/airbricks anywhere & the fact that all the walls have been plaster-boarded & plastered over but are cold to the touch how can i best insulate them? as i have been informed i should insulate before i rewire?
    i would be extremely grateful for our expert advice.

    Monday, February 3rd

  • peterfall

    Karen
    I’m afraid I’m not able to answer your questions without seeing the property and understanding various aspects of the construction. If you are in the North East of England I could give you a quotation for a defect inspection. If you are somewhere else in the uk then I may be able to suggest another surveyor.
    Peter Fall

    Wednesday, February 5th

  • Karen Roskams

    i have just bought this house in Germany; hence all my queries i want to put in a staircase to the attic & move upper tier of staircase as well is it feasible to fit in a staircase in 4 mtr wide hall when height is 220cm?
    if you know any foreign associations you could recommend i am in NRW near Moenchengladbach.

    Wednesday, February 5th

  • mel

    I’ve had my chimney stack removed and the roof tiled over because of damp on the upstairs chimney but there is a massive draft. The fireplace is not used is just ornamental I’ve boarded the underneath up to stop the huge draft, but I got a feeling I may still need some ventilation!? Is that right!? If I drill a 5″ by 5″ square area filled with holes…is this enough ventilation!?

    Friday, February 7th

  • peterfall

    Mel
    Best to let some air through and your suggested board with a series of holes drilled in sounds a good idea.
    Peter Fall

    Tuesday, February 11th

  • Rob

    I am about to get some fitted wardrobes. Where I intend them to go would block a vent on an old chimney breast. The chimney is also used as the exit point of some bathroom ventilation ducting.

    I have two options that I can see:

    1. Leave the vent where it is, and cut out a section of the wardrobe so that it isn’t blocked.
    2. Move the vent to above the picture rail (about 2.6m high).

    Would option 1 be ok? I can imagine there would be decreased airflow, but not sure if that is an issue. It is the cheaper option.

    If we went with 2, would there be any problems having the vent at a height of 3m as opposed to floor level.

    Cheers

    Monday, February 10th

  • peterfall

    Rob
    Option (1) should do it providing you can run a duct from the existing vent to the new one in the wardrobe.
    Peter

    Tuesday, February 11th

  • David Cotton

    I have a semi detached property and I am told it has a cavity wall base bit is finished with block above the ground floor with render to the side elevation. Two of the bedrooms with a wall to this side are causing issues
    with damp and mould if left for any time behind a bed head or wardrobe etc. In the box room I place ply a batten to maybe circulate some air in order to sort the problem but this has failed….what are your thoughts on this
    regards

    david

    Saturday, February 22nd

  • peterfall

    Have a look at my article on Condensation, it may help.
    Peter Fall

    Sunday, February 23rd

  • david cotton

    Read your article but can you expand on your comment “a new internal layer built within the present walls”
    as this is a bedroom in both cases.

    best regards

    david

    Monday, February 24th

  • Peter Fall

    Sorry David, which article are you referring to?
    Peter

    Monday, February 24th

  • Maggie

    We bought an old (mid 1800’s) terraced house five years ago. The front chimneys were already blocked in, both upstairs and down and the back chimneys only upstairs. We removed the gas fire from the downstairs back room and blocked the fireplace in – not knowing about vents. A year or so ago we got a damp patch on the back bedroom chimney breast and the chimey wall in the loft above was wet A builder recommended removal of the chimney pots and fitting ventilated covers. This was done about six months ago but the problem has become much worse and the wet patches have now spread to the entire wall and into the front room (ie: not only on the chimney breast). The builder is now suggesting removal of the chimney stack and the little ‘wall’ that runs frtont to back where our roof joins next door’s, then tiling over everything (at a cost of sime £4000).
    My questions are:
    Given that the damp is not restricted to the chimney breast, could this all really be caused by a lack of vent?
    If so, would installing a vent resolve the problem now, given how bad it has beciome?
    If not, is the builder’s suggestion likely to resolve the problem.
    I’d be grateful for any advice please.
    Maggie

    Friday, March 7th

  • peterfall

    Maggie
    If the damp is spreading beyond the chimney breast it is most unlikely to be a lack of ventilation to the redundant flue. As to the builders suggestion, I can’t really comment as I haven’t seen the house or the dampness. If you are certain the source is dampness coming down from above then removing all brickwork above roof level and then extending the roof tiling across would seem to be a sensible idea but you need to be certain that is the cause.
    You might want to get the advice of a Chartered Building Surveyor who specialises in Building Pathology before you do anything drastic.
    Peter Fall

    Friday, March 7th

  • Chris Roots

    Hi,
    We live in an end terraced 1920s build and have a damp problem in the back bedroom floor and top of wall next to the chimney breast. It’s the outer wall. It’s been getting worse over past few months with all the rain. Also noticed that the bricks on the gable end wall below the chimney stack are turning a white ish colour indicating damp.

    The chimney breast is no longer in use and we had the opening bricked up 6 years ago. A roofer has looked at it and believes the damp is coming from the unused chimney stack and recommended re-pointing and replacing lead flashing (which is poor – I have seen photos he took while on the roof and water could easily be getting in. He also recommended another option of removing the chimney stack and re-slating but this would be more expensive. Any advice would be appreciated.

    Sunday, March 16th

  • peterfall

    Chris
    The best advice I can give is you engage a Chartered Building Surveyor who specializes in Building Pathology. I am based in Newcastle so it isn’t economic for me to travel outside of the North East of England. Try the RICS web site for Find a Surveyor in your area.
    Peter Fall

    Wednesday, March 19th

  • Tom

    Hi Peter – I live in a 1870’s semi, two chimneys with 3 flues in each. We have stoves fitted in 2 rooms, so 1 from each stack has been lined. Leaving 4 redundant…They all have cowls on although when its a particularly windy and rainy day 2 let water in, as in one room I just boarded out the fire place and can hear it drip drip!! (i know what you are going to say there!!!) In the other I can see a slight yellowing where the opening was (I have shamefully just bricked up without a vent) – The other 2 fireplace do not appear to have any issues (i left them as they were…one boarded out, one bricke) — Given these 4 are no use, my plan is to cap these 4 and pop an ugly but i guess necessary vent in or can I just drop 4 c-caps on them and call it a job!!

    Wednesday, April 9th

  • peterfall

    Tom
    The dripping water implies the cowls on the top don’t shield the flue from rain water. A standard gas cowl should do this.
    The stacks will still absorb water through the brickwork and it is this that the ventilation should dry out, hence the need to keep air entry at the bottom and exit at the top. If you fail to ventilate the water soaking through the bricks, it can mix with any residual soot embedded in the flue and cause nasty brown staining and corrosion of the mortar joints on the upper areas of the chimney stack, down as far as the upper rooms.
    What ever you do just make sure you stop rainwater entering the flue at the top and keep air flowing up the flue.
    Peter Fall

    Thursday, April 10th

  • EG

    Hi Peter – I have recently purchased a mid-terrace brick house, built around 1905. It used to be a 2 up – 2 down, and it has the chimney breasts still intact in the front and back rooms. The front downstairs fireplace is open and has now been swept, however the back flue has been closed both upstairs and downstairs, with what looks like a basic screwed-in piece of board over the holes, without any ventilation. There isn’t any damp but we’ve been advised to get it ventilated. A few questions:

    1. What’s the best way to create a vent donwstairs – can this be done with a bit of DIY by simply drilling holes into the board? Or is it better to get a plastic vent fitted? And could I then put a piece of furniture in front of it or does it need to be kept open?

    2. I’d like to have the upstairs fire place open as it still has the mantelpiece and I expect the fire place to still be there behind the board, although it will be just aesthetic. What’s the best way to block the draft from the chimney while still ensuring a flow of air? Again, can I do this myself?

    Thanks in advance and sorry for all the questions – this is my first house so it’s all very new to me!

    Thursday, April 24th

  • peterfall

    EG – Do you have a name? I don’t like responding to anonymous questions.
    Peter Fall

    Wednesday, April 30th

  • peterfall

    Enfys
    1. There are plaster vents made which can be set over the hole fixed with polyfiller and it will look a little more attractive than just a bit of board. Providing you place say a chair in front, with a gap of at least 150mm to the vent then that is ok. What you shouldn’t do is build a cupboard around the vent as this will restrict the air flow too much.
    2. You could fit a panel into the underside of the flue with the holes drilled into it to retain the small air flow but stop the draughts. Plug and screw a timber frame around the flue then screw the panel to the frame. The panel will need to be removable but beware dirt will drop down the flue and through the holes, eventually blocking them. If you can fit the panel on a slope of say 40deg. then the dirt will collect at the bottom of the slope leaving the holes on the upper part free to allow an air flow through and when you remove the pane, say every 12 months, the dirt will be collected from the down slope side.
    Peter Fall

    Wednesday, May 7th

  • EG (Enfys)

    Sorry – my name is Enfys.

    Wednesday, May 7th

  • Mary

    Dear Peter,

    I just moved a new tenant into one of my property’s yesterday. It is a bedsit and the living room/bedroom has a vented internal chimney. We have never had any problems with dampness or anything and the chimney is in an internal wall so external ventilation is not an option. The new tenant however is insisting that this is a health hazard. Is there known health problems associated with internal wall ventilation?

    Thursday, May 22nd

  • peterfall

    Mary
    I know of no health hazards attached to providing ventilation to a room. The air flow will be out of the room rather than into the room.
    Peter Fall

    Thursday, May 22nd

  • Cristina fox

    Hi Peter
    We have only been in our house for about a year and have had an ongoing problem with damp and condensation. We had our walls injected and cavity walls cleaned out. The house was built around the 1930, we bricked up the old fireplace without leaving an air vent as we didn’t know any better and this was when condensation and mould started on and around our windows. If we remove the chimney at the top will this helpwwith condensation as we can’t even see out of our windows some days. Any advice would be appreciated as money is extremely tight and I am worried about my young children’s health.
    Thanks

    Wednesday, May 28th

  • peterfall

    Christina
    I fear that the ventilation through the stack will only partially tackle your condensation problem. You need to get rid of the moisture you generate as and when it is produced. This requires discipline in opening windows or putting on fans as well as closing the doors to the rooms where you produce the moisture. In addition you will need to consider how you heat the house and the level of thermal insulation in the roof, walls and windows.
    Can I suggest you contact a Chartered Building Surveyor who is experienced in Building Pathology matters and is local to your house and ask them to visit your house to carry out an inspection and discuss how you use it.
    Peter Fall

    Friday, May 30th

  • Steve Ruff

    Hi Peter
    I installed a multifuel stove with a liner , for a customer 8weeks ago , into an older property with a central chimney that has two flues ( no clay lining } , separated by a midfeather dividing wall . One flue serving the stove , the other is to the kitchen which presumably was for a cooking range etc this flue had been capped off with cement ,and the pot removed ,with no ventilation at the kitchen or in the stack and left for years .On the advise of the customers surveyor , at the time of fitting the stove , I installed an air brick to the unused flue , just under the sailing course .
    The problem is not damp but a chemical type smell in the roof area which is leaching through the bricks , I am convinced its because the unused flue has been decaying for years , all the sulphur and creosote is now drying out with the air vent , and now of course the lined flue to the woodburner is getting the stack warm ,also I ventilated the lined flue as per manufacturers instructions ,
    my question is – would it help to fit a vent in the kitchen to the unused flue and , could the bricks in the roof area be treated with sulphate resisting primer then parged or cement rendered to hold back the smell? or any other advise would be most helpful .
    regards
    steve
    The prob

    Monday, June 2nd

  • peterfall

    Steve
    This isn’t something I can give you direct advice on as I haven’t seen the property nor ‘smelt’ the effect!
    If you vent a flue it’s important to have a vent at the bottom and the top. Just the top will not give a free flow of air through the flue.
    If you are convinced the smell is caused by salts coming out of the flue and stack then you can apply a sulphate resisting barrier to the faces of the stack to hold it in. The use of a sulphate primer and then a sulphate resisting cement based render will do the job but make sure you clean off any loose and friable surface from the stack before you start or it will just fall off. Beware, as it could cause the salts to migrate down into the room beneath. It may be better to vent the roof space and let the salts come out of the stack at that point.
    Peter

    Wednesday, June 4th

  • Claire

    Hi Peter

    I am a first time buyer and have recently had our home buyers survey returned to us. It has raised the issue of the fire places and ventilation. The property is a two bedroom 1930’s semi. It was owned by an Elderly couple but has recently been renovated. The current owners have blocked up the fire place but haven’t put any vents in. Apparently this can cause condensation which in turn can increase the risk of damp.

    The report says : the property includes a number of chimney breasts, the fireplaces have been removed and the openings sealed off and have no ventilation. When a fireplace has been taken out of an external chimney breast and the opening blocked up, the following work should be done: the top of the flue at the chimney level should be fitted with a terminal fitting that keeps out the rain but allows ventilation of residual moisture in the flue. The fireplaces should be fitted with a hit and miss vent. You should do this soon. Any disused flues should be checked and swept before use in the future.

    Before we proceed with the sale, we are trying to establish if this is a big job- and whether it should be undertaken by a builder or a chimney specialist or even if it is something we could do? This is so we know whether to negotiate with the seller or do the work ourselves. The shape/ outline of the fireplace is still there, so it may be that we could insert an air brick/ vents in the top of the fireplace- therefore meaning they are out of view. However, there are four hollow fireplace outlines in the property and we wondered if each of these would need to be ventilated?

    Thanks in advance.

    Sunday, June 15th

  • peterfall

    Claire
    This is not something I should get involved in. You have a professional advisor in the surveyor who carried out the Home Buyers Survey, please use them. They know the property and the area and they are your surveyor. Follow up questions such as this should not incur any further fees.
    Peter Fall

    Monday, June 16th

  • Claire

    Peter

    Thank you for responding. Unfortunately the surveyor- instructed via the building society who has offered our mortgage- has indicated that it is not something he can help with further. He is unable to advise who should carry out the work and what needs to be done to rectify any problem other than quote the standard paragraph in the report back to me. Needless to say, I have contacted the surveying company!!

    Thanks again for your time

    Claire

    Monday, June 16th

  • Tim

    Hi Peter,
    I wonder if I may ask a peice of advice, we have removed an old baxi back boiler from our living room and would like to instal a mock wood burner (Dimplex electric fire) in the now open fireplace recess that was the old boilers location, the chimney liner is still in place with a secure liner cap in good condition on the top of the stack, I would like to plasterboard the recess and fit a hit and miss vented lid; screw fitted from below to allow periodic cleaning , is it ok to dab and board plasterboard directly to the visible side and back brickwork (not as far up as the lime render) to maximise the useable space and provide sufficient clearance for the new fire? we live in a 1932 ex-council semi, hipped roof with a central back to back stack, the two upstairs fireplaces are both blocked and vented and have been for over 40 years.
    I would appreciate your advice and thank you in advance.
    Kind regards
    Tim

    Monday, June 23rd

  • peterfall

    That seems fine but you might want to consider a louver plaster vent instead of the hit and miss as it looks better.
    Peter Fall

    Tuesday, July 8th

  • Fran

    Hello Peter.

    I have worked out my chimney breast as hydroscopic salt damp patches. The chimney is open however I have never had it swept of a fire lit ( I have been here 11 years). If I did both these things would the patches disappear ?? I don’t want to replaster the chimney breast.

    Thursday, July 10th

  • peterfall

    The simple answer is no as the salts have migrated from the soot in the flue into the brickwork and now are embedded in the plaster.
    Sorry.
    Peter Fall

    Thursday, July 10th

  • Pete

    Hi Peter,
    I have just moved into a 1936 house which has two chimney stacks, one which serviced the front reception room and the bedroom above and one which serviced the back reception room and bedroom above that. The problem I have is that the previous owners had the chimneys removed and capped in the loft space when they replaced the roof. As it stands there is one fireplace remaining for aesthetic reasons and the other three have been boarded over which is causing damp to appear around these breasts. To further complicate the problem the next door neighbours have built to within 100mm of the external chimney breasts making them impossible to get to. What would be the best way to remedy this?
    Thanks,
    Pete

    Monday, July 14th

  • peterfall

    Pete
    I’m sorry but I can’t advise you on this one. I would need to see the house to determine its construction, exposure and the pattern of the dampness to be able to reach a conclusion.
    Dampness will occur from a variety of causes,
    -rising from the ground because of a lack of damp proof course,
    -penetrating through a wall because of inadequate thickness of wall, poor pointing, leaking gutters etc,
    -excessive humidity causing condensation or being absorbed by hydroscopic salts embedded in the plasterwork
    and so on. Each of these having different symptoms and effects.
    If you are in the Tyneside area I would be happy to inspect and report but otherwise can I suggest you contact a Chartered Building Surveyor local to you that carries out residential Building Surveys. Try the http://www.rics.org website for names.
    Peter Fall

    Tuesday, July 15th

  • Chris Mason

    Hi Peter – looks like a popular thread

    we’ve just moved in to an old 1870s solid walled flat conversion, and i was wondering if there was anything i could put in the air vent / brick cavity that would help to minimise noise and draughts

    (going to get some hit and miss vents, but just not sure what, if anything could help)

    Saturday, July 19th

  • peterfall

    Chris
    If your noise problem is from outside then yes there are noise attenuating air vents available. Not cheap but they do work providing you have sound proofed the windows and any other holes that can let sound through the wall.
    It is very difficult to reduce the amount of sound passing through the structure of a building without major works to the walls, floors and roof. This is not the place for me to launch into a detailed explanation I’m afraid but I suspect the cost and disturbance of the necessary works would not be worth while.
    Peter Fall

    Monday, July 21st

  • Craig R

    Hi Peter,
    Wondered if you can help. We have a early 1900’s 2 bed mid terraced house and are suffering from efflorecence on the rear chimney breast. It’s on the right hand side of the front face about 50-70mm in from the right edge, and 700mm up from the floor. It’s around the same height on the actual right hand side too. We had a Wycamol injected DPC done around 4yrs ago, and the whole chimney breast (up and down) has been completely blocked off (with a flat face) since before we moved in 10yrs ago. The efflorecence has now been visible for about 2.5yrs, and I just keep brushing it off and painting over it. There’s also a damp patch appeared over the last 12 months about 1700mm up and 450mm in. I don’t think the two are related as, although they’re on the same breast they are quite far apart. I know the pots aren’t capped and although I haven’t actually been up to check, I can’t see any obvious damage to the stacks and the pointing (from what I can see) looks ok. I appreciate you’re working blind, but do you have any ideas or suggestions as to what could be causing the efflorecence, and/or damp patch? We were considering taking the breast back to brick and re-sealing it with a waterproofing agent and re-plastering, but would like to avoid that if possible as we have two young children so could do without the dust, dirt and upheaval if we can!!!

    Cheers
    Craig

    Sunday, July 20th

  • peterfall

    Craig
    Thank you for the enquiry but despite giving me lots of information there are still many questions from me that can only be resolved by seeing the defects. However you say that the chimney breast was treated with an injected dpc 4 years ago but you don’t say whether the wall was replastered and more importantly with what type of plaster. If the dpc is working then the wall will take a couple of years to dry out and as it does so the salts that are in the rising damp will migrate to the surface of the wall and leave a deposit like efflorescence. Any replastering after the works should have used a retardent to resist this but I suspect the replastering wasn’t done or you would have said.
    You don’t say whether the damp is up from floor level to 700mm or whether it starts 700mm up from floor level. If its up from the floor then the dpc may not be working and you may need to go back to the installer.
    I assume the house is 2 storey, you don’t say, therefore it is most unlikely that the source of the damp is from the top of the flue. On the otherhand you also don’t say if the damp problem is at ground floor or first floor level.
    Sorry but the best advice I can give is to call in a Chartered Building Surveyor who specialises in Building Defects. Try the rics.org website for find a surveyor.
    Peter Fall

    Monday, July 21st

  • Jean jones

    Hi Pete
    Thanks for the article its always good to have experienced advice. I have bought an old terraced house. The chimney breast in the room has been skimmed and the hole where the fireplace was has been kept with the sides and back of the hole plastered. Therefore leaving the fireplace open with the chimney open too.

    We were anxious about any soot fall and also the heat loss through the chimney and so my husband put in place a piece of aluminium with holes drilled in it. He also put a lot of fiberglass insulation above it (up the chimney) in order to keep the room warm.

    Now we appear to have patches below the level of the blocked chimney on the plastered inside of the hole where the grate was.

    I would have thought if blocking the chimney had caused a reduction in airflow and resulted in damp patches – then that would show above on the chimney breast.

    We are going to take away the blockage and see if it clears but just wondered if you had any advice. Many thanks Jean

    Thursday, August 28th

  • peterfall

    Dear Jean
    Difficult to say but it sounds like you plastered over the old fire back which will be impregnated with soot deposits. These deposits could be causing the patches as salts in the soot are hygroscopic and absorb moisture from the atmosphere. Nothing you do to the flue would fix this.
    Peter Fall

    Thursday, August 28th

  • Ray

    Hello Peter, I wonder if you can help? We have a 3 bedroom detached bungalow, that was extended sideways to increase the overall footprint by the previous owners. At that time, they capped the chimney breast in the loft just around the mid point of the loft height between loft floor and the height of the height at the rafters. The chimney breast is in the way now that we want to begin opening out and using the loft area.

    The chimney has remained unused since we bought the property 10 years ago, although we did install an electric effect fireplace in the lounge below. The chimney stands in our loft and I’m wondering that if I began to remove it brick by brick, whether I should seek any professional advice before undertaking this?

    Thanks in advance for your kind help,

    Ray.

    Thursday, August 28th

  • peterfall

    Ray
    Stop, stop stop… Don’t remove any bricks until you take advice from a structural engineer. This breast and the flank walls could be holding up the roof.
    Peter Fall

    Thursday, August 28th

  • Nick

    Peter,

    I am renovating a detached Victorian property which is needing some tlc. This web page has been an excellent read but I am now a bit confused about the plans proposed by architect and builder with regards the fireplaces/flues. I will try and be concise:

    On the ground floor I intend to use a fireplace in each of the two living rooms by installing multi fuel stoves with a suitable flexinliner and cowl. The remaining fireplaces and flues on this floor and the first floor will be redundant and my intention was to remove them. Some are already closed off and have a hit and miss vent low in the wall.

    It was planned that the chimney stacks would be rebuilt for peace of mind and incorporate a lead safe at roof level leaving just the single flue/pot per gable open for the proposed stoves. There would therefore be no possibility of rain entering the unused flues; however there would neither be any passage of air to the outside. I was informed there would be no issue in thereafter getting rid of the room vents throughout and this suited both aesthetically and practically for some planned room layouts where large pieces of furniture would block the vents at low level.

    From everything I’ve read above there may be issues with this approach but I would be grateful on guidance before going much further. Surely if the unused flues are sealed off at the top it is a moot point to introduce airflow further down from within?

    Finally, there is a third chimney stack to the rear previously serving the kitchen but this will not be utilised at all and therefore taken down below roof level and slated over. What needs dine in respect of the remaining voids for the flues that seved this stack?

    Any advice would be much appreciated!

    Regards,
    Nick

    Saturday, August 30th

  • peterfall

    I’m sorry but this is not something I should get involved with. I suggest you follow the advice your architect gives you as that is what you are paying for.
    Peter Fall

    Monday, September 1st

  • Rob

    Hi Peter,

    We are intending to construct a cabinet recessed into a disused fireplace. We intend to fit a vent in the toe board and allow air to flow up behind the rear wall of the cabinet and up the original chimney hole via a gap above the top of the cabinet. The chimney hole would be covered by mesh. Would this provide sufficient ventilation? Would it help to have actual ducting run from the toe board vent to the chimney hole, behind the cabinet?

    Aesthetically, we would prefer to avoid a vent in the wall above the fireplace / cabinet, but would this be a significantly better solution?

    Many thanks,

    Rob

    Thursday, September 11th

  • peterfall

    Rob
    As long as the mesh isn’t too tight and the hole isn’t too small it should be ok. Don’t forget you need a vent at the top as well or the air won’t flow.
    Peter Fall

    Tuesday, September 16th

  • Rupert

    Peter,

    Ive just bought a old victorian terace property(Essex).

    The property has three chimneys – 2 of the chimneys are blocked up on first floor, but open/covered up with ethier a back boiler on one, and a gas fire on the other.

    I will be removing the back boiler and gas fire from both, as i am changing to a combi system.

    My question is, if i have the ground floor ones open with a Vent for air flow, do i also need to put in vents for the upstairs ones which are currently blocked up(timber board)

    My other question leading on from this is – If i do have to vent the first floor ones aswell, could i just put a Chimney Sheep in all 4? as this will give ventilation aswell as stop drafts?

    Look forward to your response.
    Thankyou
    Rupert

    Thursday, September 11th

  • peterfall

    Rupert
    Each of the flues is separate so each of the three should be vented.
    I don’t know what a chimney sheep is I’m afraid so I can’t comment on that.
    Peter Fall

    Tuesday, September 16th

  • niall

    i live in a 1930s bungalow with 2 chimneys breasts on the exterior, both fireplaces are removed. in one room water appeared on the floor were the grate would have been and i was advised that the chimneys were in bad condition. both have now been removed to below roof level and roofed over. i now have a damp spot where the ceiling wall meets in both rooms. one has an exterior vent at the bottom and the other still has an open fireplace. my question is do i need air bricks or similar at top and bottom on the exterior or interior

    thank you

    Thursday, September 18th

  • peterfall

    Niall
    I think it is probably too late for air bricks as the damp may be the result of salts that have migrated from the flue to the plaster. The salts are hygroscopic so would take moisture from the atmosphere.
    My problem is I haven’t seen the damp, the building and it’s location so I can’t give you good advice I’m afraid.
    Peter Fall

    Thursday, September 18th

  • Neil

    I live in a semi detached Victorian house with two open fire places downstairs , the upstairs fireplace’s are sealed/ plastered with an air brick fitted .The problem I’ve got is that when it rains or its a damp day the outside Wall sweats at the places were the chimney flues are situated from the ground up wards , I’ve put in brick vents into the flue on the outside wall but it hasn’t made much difference . The chimney pot caps are all present with vents in them , thanks any advise

    Monday, September 22nd

  • peterfall

    Neil
    Obviously can’t say anything with any certainty as I haven’t seen the house and the problem but one of the reasons the wall appears damp could be the soot salts that have migrated from the flue to the outside face of the chimney. These salts are hygroscopic and will absorb moisture from the atmosphere, especially when it rains. Once embedded you’ll not get the salts out without replacing the bricks. If the wall is plastered or rendered then sealing the wall with a sulphate resisting solution and then re-plastering or rendering with a base coat of sulphate resisting cement render will hold it back.
    Peter Fall

    Tuesday, September 23rd

  • Daniel Higginson

    Hi Peter,

    I have recently moved in to a split level ground/basement flat that has been poorly refurbished over the years and now I’m trying to solve the problems. The building is circa 1880s and has two bedrooms, one above the other and both appear to have once had fireplaces. Both are probably bricked up but with no air bricks in place. What complicates matters is that a damp proof membrane sits on top of both fireplaces. Both fireplaces appear to feed in to the stack which is on a landing level. Damp patches have appeared on one side here and salts through on the other side of that wall. Is it possible to insert an air brick on the landing level or will it cut out ventilation to the two fireplaces? Any suggestions please?

    Friday, September 26th

  • peterfall

    Daniel
    I fear it may be too late. The salts could be from the soot in the flue which have migrated with moisture to the surface of the chimney breast. These impregnated salts will absorb moisture from the atmosphere and constantly appear as damp.
    The air vents are to keep the flue dry once it is redundant and stop the migration of the salts in the first place.
    You now need to remove the affected plaster, seal the brickwork with a sulphate resisting primer then apply a sulphate resisting cement based render to the wall before finishing with plaster.
    If you do insert vents then each previous fireplace needs its own vent and the chimney pots need to be kept open to let air out at the top.
    Peter Fall

    Friday, September 26th

  • Jennie

    Hi
    Hope you can help with my issue.
    4 years ago was having water in, had to put a bucket in the attic. Roofer removed shared chimney left a flue there for my neighbour.
    4 years running I have called them back out as I’m still having damp patches on the top of my chimney breast in the back bedroom and damp patches on the alcove next to chimney breast. No damp anywhere else.
    1st the re sealed everything, 2nd they have removed a few bricks in my attic for ventilation.
    They have looked in the Chinese breast and can’t see anything wet each time they come.
    Both chimney breast a down stairs are blocked off, I have a hole in the wall with lights downstairs showing no signs of damp so just the bedroom,
    On to the bedroom the walls are dry lined dot and dab! Plaster over the top.
    Patches ain’t siaking just look like loads of wet patches and it stains the wall.

    I’m at the end of my tether no one knows what my next course of action is any ideas thanks

    Wednesday, October 1st

  • peterfall

    Jennifer
    It isn’t possible for me to give you an accurate diagnosis without seeing the problem first hand. It does sound like salt affected plasterwork but there are other causes which an inspection by a chartered building surveyor would consider.
    Where an old flue has not been fully swept when it was finished with and then left unventilated then the salts which were in the soot become damp. The moisture soaks into the brickwork of the chimney breast taking with it the salts and it dries out in the outer plasterwork and brickwork of the breast.
    The salts are hygroscopic and with absorb moisture from the atmosphere making the wall damp and producing stains. No matter what you do to the flue the damp stains won’t go away. The only thing you can do is remove the plaster, treat the bricks with sulphate resisting primer the replaster with a render coat using sulphate resisting cement.
    Peter Fall

    Sunday, October 5th

  • Brian

    Peter,
    My daughter lives in a 1920s, ex council flat. There are 3 old chimney breasts that have been blocked off. Plastic grills allow ventilation but I have noticed grey wool like material on these grills. I am afraid that it is asbestos so I have temporarily taped off the grills with duct tape. Could I be right and how would I confirm that it is asbestos?
    Thanks,
    Brian

    Saturday, October 11th

  • peterfall

    Brian
    I really would not like to say without first seeing and touching it and then if need be having it tested.
    It could quite easily be fluff so I wouldn’t get too excited about it.
    Peter Fall

    Sunday, October 12th

  • Brian

    Peter,
    Thanks for that. I was concerned because I knew that some chimney liners could contain asbestos and I thought that they might be deteriorating after all these years of lack of use.
    Thanks,
    Brian

    Wednesday, October 15th

  • sharon

    hi peter,
    could you please advise me on a problem my mom has with her semi detached house she has lived in property over 20 years and never had this problem before the house was built in 1920 or there about . there is damp in back bedroom wall on chimmy breast and also goes down to lower ground backroom on sides of chimmy breast, there is no vents on chimmy breast never have been, she has had chimmy pointed and new flashing done on her side of chimmy new pots put on top of chimmy. the problem is still happening could it be the next door neighbours that could be the problem both fire places are not in use they have electric fires the problem is not in her frontroom fireplace or front bedroom only on the back of her house, i really do not know who to phone about this problem for her, my mom lost my dad last december suddenly and is so depressed because my dad was always the one to sort the problems out for her, she owns the property any advise you can give me will help so i can sort this out for her thanks sharon

    Saturday, October 18th

  • peterfall

    Sharon
    this is a difficult one that needs an inspection. I suggest you contact your nearest chartered building surveyor and ask them to inspect the problem and give advice. Try http://www.rics.org and search for find a surveyor.
    Peter Fall

    Monday, October 20th

  • Becky

    Peter
    I have been reading through the above comments and I am confident in knowing what has been casuing the apparent damp patches on my downstairs and upstairs chimney breasts. We live in a sold brick Victorian semi-detated property. The patches are more apparent when its been raining and when we are cooking in the kitchen and I understand this is because the salts are attracting the moisture from the air. Neither chimney breast are in use and indeed, it has been recommended to us that we have a vent fitted in the downstairs to help with airflow. We’ve not got round to this yet! I am aware from reading the thread that the only option to correct the problem caused by the salts is to remove the plaster, treat the bricks and re-plaster. However, our finances unfortunately don’t permit us to be able to do this at this stage. We’ve only been in the house a year and we suspect it was recently plastered before we moved in (unfortunately with a thermally inefficient cement plaster which is very cold to the touch!).

    The question I have is, in your experience, is will the patches get worse if we leave it as is? Or is it something that one can live with? At the moment, we only notice when there’s moisture in the air – there doesn’t appear to be any permanent staining to the paintwork/plaster….yet! Secondly, we don’t have any mold forming on the chimney breasts, but I wondered whether this kind of problem is also asociated with the formaltion of black mold (in a similar way to condensation?). Any advice would be much appreciated. Thank you!

    Monday, October 20th

  • peterfall

    Becky
    I can only expect it to get worse with time I’m afraid.
    Condensation will be a problem if you don’t control the level of humidity in your property. Ventilate any room where you generate high levels of moisture, kitchens, bathrooms and keep the door closed when you do it to contain it in that particular room. Don’t let it escape into the rest of the house.
    Peter Fall

    Monday, October 20th

  • Steve Doyle

    Peter

    I’ve got two damp patches covered in white furry mould that have just appeared in the recent wet weather. They’re on the internal wall of a room, on the wall directly outside of which is attached the soil down pipe from the upstairs bathrooms. This pipe comes down into the concrete in a corner next to a wall attached to the house. There’s also a noticeable big damp, green, damp patch spreading up the wall from that corner. Could the pipe in some way be causing these internal damp patches, perhaps by being blocked? I can’t see water leaking from the pipe when it’s in use.

    Monday, October 20th

  • peterfall

    Steve
    I’m sorry but I can’t help on this without an inspection to understand the construction, direction of drain runs and its exposure to the weather.
    I suggest you call your local chartered building surveyor to call out and inspect the problem area.
    Peter Fall.

    Monday, October 20th

  • Laurie

    We have a fireplace in the living room that we don’t use. It does not throw heat and is more ornamental. Our problem is what appears to be black mold on the outside of the chimney and below it on the exterior wall. I’ve had one opinion to cap it but I’m not sure of this. There is still the mold problem. Any help would be appreciated.

    Thank you so very much
    Laurie

    Thursday, October 30th

  • peterfall

    Laurie
    I don’t think I can help on this one. I think you are based in Canada (@shaw.ca) so your chimneys are possibly different to ours in the UK.
    Here in the UK our problem is soot residues from years of burning coal. These residues need to be kept dry otherwise the chemicals in the soot absorb moisture and tend to migrate through the brick or stone walls of the chimney to the outer faces, that’s inside the house and out. Once the chemicals are embedded into the brick and stone and then the plaster finish they continue to absorb moisture from the atmosphere giving a brown sometimes tarry stain that is damp.
    Using the flue keeps the soot residues dry inside the chimney so they don’t tend to migrate but once you block off a flue the soot chemicals absorb any moisture and then go walkabout through the masonry! I therefore always recommend to my clients to leave a vent at the bottom of the flue if they brick up the fireplace and to put a ventilated cap on top to keep out rainwater but still allow air to flow through.
    Your black mould could be from a lot of sources, none of which are to do with the soot chemicals. I’m afraid I would need to inspect the building and discuss how you use it and the chimney before I could give you advice. Sorry.
    Peter Fall

    Friday, October 31st

  • andrew

    Peter

    I wonder if you can help, My daughter has an end terrace victorian house. In the back bedroom is a redundant fireplace. Just recently Damp patches have appeared from the ceiling to a depth of about 1/2 meter to right hand side of fireplace.

    I have been into the loft and it appears dry, even to the extent of taping kitchen roll around to see if its damp (It isnt !) I cannot believe that there is penetrating damp from outside as the damp forms an exact horizontal line at the celing ( But no damp above it in the loft just above where the plaster would start)
    The roof has had the lead flashings replaced previous to the sale to the satisfaction of the surveyor, although he did indicate that there was damp present in the wall concerned, and sugguested it could take months to dry in an older house such as hers. (Incidently, the patches get worse about 3 days after rain)

    It has been fine from Feb this year & the problems started mid Oct ?

    Andrew (Taunton)

    Tuesday, November 4th

  • peterfall

    Andrew
    Obviously I don’t know your house or the environment it’s in so I can’t give you any advice on the damp problem you are suffering. I can say that the reason we recommend air bricks in bricked up fireplaces is to stop the salts from the old coal soot from mixing with moisture in the flue and migrating to the face of the chimney and any attached ceilings. These salts are hygroscopic and therefore in damp conditions will absorb moisture from the atmosphere and become damp patches, just at the position you describe.
    Over the years water will run down the flue from the top and gradually mix with the soot.
    If the salts are the problem then only by removing the affected plaster on the walls and ceiling, applying a sulphate resisting barrier then a coat of render using sulphate resisting cement might you be able to resist the salts. Once in the wall they will continue to try to migrate to the surface. An alternative is to remove all of the plaster to the chimney breast and refinish it with plasterboard supported on an independent frame, i.e. not touching the wall.
    If in doubt engage a local Chartered Building Surveyor to inspect and report on the problem.
    Peter Fall

    Tuesday, November 4th

  • sam

    Dear Peter.

    Had a Dam problem due to water damage on one side of the wall where the totally sealed of chimney stack is. Got a few people to look at it including a surveyor.. And Later found there to be a whole to the outer Render of the Chimney stack where the water might have come in. Sealed it off.. But most of these people also pointed out to me a Air Flow Brick. Which is totally blocked off from the inside of the house. but not outside. The Air Flow brick Sits where the chimney stack wall. Should the outer Side be blocked as well as many also said that might be a cause of damp, since the inside is blocked?

    Monday, November 10th

  • peterfall

    Sam
    Sorry but I’m having difficulty understanding what you are trying to describe.
    You say you have a Dam (damp?) problem on a sealed chimney breast which a number of people have looked at and most have said there is an air brick (somewhere) and you don’t know whether it should be blocked off to stop the damp.
    The answer is I have no idea without seeing the house, the damp and the air brick.
    Peter Fall

    Tuesday, November 11th

  • Sam

    Hi Peter,
    Sorry for the confusions. Basically in the spare bedroom the wall facing outside were the window is, the plaster on this wall has started to bubble and to the left this wall is showing sign of a Brown Water stain to the corner which joins to the wall with the bubbled plaster. Above this room there is an old chimney that has been capped off, Leading into this room from the outside is a square shape air brick just above the window area, but for some reason the inside part of the air vent seem to have been closed off, and plastered over. We have had many people come and of course all say we are suffering from damp. But my concern is that some people have stated that as the Air Brick is blocked off from the inside and is only open from the outside water could be getting trapped between these walls so i have been told to block this off. Whilst other have said not to do this and have suggested opening the inside, some have said this may not even be the problem. So this is my first problem also their were many cracks to the top of the chimney which have now been repaired as most people thought that this was the cause of the brown water stain area and even maybe the cause of bubbled plaster. I have marked this area with a pencil in hope that the water staining does not spreed further Should this stain mark rescind if the wall is drying and no more further water leaks. Any advice would be gratefully and sorry for taking your time.
    Sam

    Tuesday, November 11th

  • peterfall

    Sam
    I need to start this with the last comment I made to you and that is I cannot be specific about your problems without first seeing the house, the defects and the environment the house is in
    Having said that you seem to be talking of two separate issues, one is the air brick and the second is the damp patch. If I start with the brown stained damp patch, you say in your messages that the stain is on ‘a sealed chimney breast’ and there is ‘an old chimney above this room’. If the stain and damp are at the top of the chimney breast and the old chimney is built on the eaves of the house directly above this room rather than at ridge level, then the stain and damp could be from salts. When you stop using a flue that previously had a coal fire, it is important to maintain an air flow through the flue so that any dampness that gets into the stack and onto the remnants of soot is quickly dried out. If you don’t ventilate the redundant flue the water and soot mixes, the result migrates through the brickwork and dries out in the plaster on the inside. This water/soot mixture has salts that are hygroscopic which continue to absorb moisture from the atmosphere and cause the damp stains.
    If the salts are the problem then only by removing the affected plaster on the walls and ceiling, applying a sulphate resisting barrier then a coat of render using sulphate resisting cement might you be able to resist the salts. Once in the wall they will continue to try to migrate to the surface. An alternative is to remove all of the plaster to the chimney breast and refinish it with plasterboard supported on an independent frame, i.e. not touching the wall.
    Turning to the air brick, this was originally built in to provide fresh air to the occupants of the room and combustion air to the previous fireplace. Previous occupants have blocked it off to stop the draughts. It is unusual for the air brick holes to be a source of dampness but if the room is now draughtless then condensation could occur in the room and this could appear as damp staining at high level with brown and black spots of mould.
    These are just two possible causes of the damp problem and until I inspect the house I cannot discount either or even other causes, such as related to your defective external render. If you are based withing 30miles of Newcastle I would be able to inspect for a reasonable fee but I suspect you are somewhat further away, in which case I suggest you look up a local Chartered Building Surveyor and instruct them to inspect and report on the problem.
    Peter Fall

    Wednesday, November 12th

  • John

    Hi Peter
    Last year i moved into my mothers house after she passed away and did upgrade work, the house is 1950’s end terrace. I had a new roof fitted and the kitchen fire place has been blocked up for over ten years.
    i replaced the gas fire in the living room with an ornamental electric one and i have noticed dripping in the evenings, i had a chimney company out to put a cowling on the pot but the dripping has only reduced not stopped.
    The dripping is not when it rains so i think it is condensation, i read your article about a vent to allow warm air flow which is something i do not have, i can only think the gas fire design allowed the air flow.
    My question is” if i was to have the chimney removed should i remove it in the attic as well, as removing the chimney should remove any risk of damp.

    thanks
    John

    Tuesday, November 18th

  • peterfall

    John
    I’m afraid I can’t answer this one as I don’t know what the cause of the dripping is and therefore can’t say that removal of the chimney stack above roof level and the breast in the attic space will remove any risk of damp. Damp can occur from many sources so removing the stack and breast will eliminate some causes but not all, especially your dripping noises.
    I suggest you call in your local Chartered Building Surveyor to inspect the house and the problem and recommend the repair.
    Peter Fall

    Thursday, November 20th

  • Lynne McGowan

    Peter I have a blocked up fireplace and a vent placed correctly but now i cant keep my room warm. The room has two radiators 2 doors and 2 opening windows…did i still need the vent?
    How can i stop the icy cold wind coming into my room through the vent?

    I look forward to hearing your advice.

    Thanks.

    Sunday, November 23rd

  • peterfall

    Lynne
    Two points, firstly to have a ‘wind’ blowing through the vent you must also have a serious leak of air out of the room, as the room will not keep admitting air unless it also exhausts the same amount out of it. Look for where you are leaking air around windows and doors.
    Secondly the idea of the vent is to get warm air to go up the flue to keep the inside of it dry. Cold and probably wet air coming down from outside can mix with the soot residue and give rise to salts and damp staining on the chimney breasts. Can I suggest you look into fitting a cowl to the chimney pot that will resist ‘down draughts’.
    Peter Fall

    Monday, November 24th

  • Chris Hain

    Hi Peter. We have recently bought a 1st floor flat in a Victorian villa and have just noticed a large damp patch on the old unused chimney running up internally up the back bedroom the full height of the tall room. There is no staining but the paint is damp and new paint does not dry. There is no fireplace in the bedroom but an upside down air brick. Thinking there was a leak of rainwater down the chimney or a flashing leak I went to see the owner below to see if he had problems too. He had in the past, told soot build up and condensation which was rectified by a damp proofing co. It appears he has blocked the fireplace up and there are no signs of ventilation. I checked in the attic and found the chimney is capped at floor level within the attic and is dry. I can feel a small draught into the bedroom but have no idea where else the chimney will be ventilated.

    Does this sound like a ventilation issue or could it be another cause of damp? What solutions could I employ, especially if flat below won’t add to ventilation? Could I remove fill, or open the chimney up from my floor to ceiling or are there likely to be structural implications? Thanks for great site.

    Tuesday, November 25th

  • peterfall

    Chris
    I can’t be specific on this without inspecting the problem and the building. I think you are saying the chimney breast and therefore at least one of the flues runs from ground floor level up to the attic where the upper stack has been removed and the top of the flue is capped off.
    There are many ways a wall can become damp but if the external pointing is sound and the chimney stack has been removed then it could be the salts from soot embedded in the flues from the old fireplaces. Once a fire is blocked off and there is no warm air rising up the redundant flue to keep the soot dry then over the years rainwater draining down the flue from the top will mix with the soot and migrate to the outer face, inside or outside the house. This mixture is hygroscopic and once embedded in the brickwork and plaster it will continue to absorb moisture from the atmosphere, even though the chimney stack has been removed. This could be a cause, in which case you need to remove the plaster, seal the bricks with sulphate resisting primer and then apply a render using sulphate resisting cement before re-plastering. If it is the cause the air bricks will be of no use now.
    You could remove the chimney breast altogether, if the breast and stack in the attic has already gone, but beware, the soot embedded brickwork will be on the outer wall as well so better to apply a plasterboard wall internal to the existing wall with a gap between to stop the salts migrating into the new plasterboard.
    If all of this is confusing I suggest you contact a local Chartered Building Surveyor to inspect and give advice on the cause based on what they can see rather than my on-line pontifications!

    Wednesday, November 26th

  • Karl

    Hi Peter, I’m not sure if this is still active but seems such a useful resource I thought I’d ask on the off chance. We have an early 80’s detached house, block & brick construction with dot & dab internal plasterboard. We had a horrible 80’s gas fire removed from the lounge and the iron supply pipe capped by a Gas Safe chap. Long story short we wish to re-board the whole wall, blocking the precast opening (620x320x95). The dot and dab wallboard has been removed and reveals a badly laid concrete block flue to loft level where galvanised pipe then continues to a ridge vent. I plan to use fermacell boards over battens and SuperQuilt insulation, perhaps with Cellotex to fill the opening. Is that feasible or do we have to install a vent?
    Many thanks!

    Wednesday, November 26th

  • peterfall

    Karl
    If the flue hasn’t been used for a coal or coke fire then I don’t see the need to ventilate it.
    Peter

    Wednesday, November 26th

  • sam

    Dear Peterfall
    Thank you very much for the reply. Unfortunetly I live way Down South. But will Take your Advice. We did intially have a surveyor sent via the insurance company. He Assembled A digital camera to a Long Pole and took some pictures. and found a hole to the outer Render( Pebble dash) of the Chimney stack. We got a Builder to reponit and fill the hole with cement, and yet this Brown Stain spreads (Drew a Pencil Mark).. I did get some Roofers and a chimney Person to look at the problem, many said the roof was good, and no crack Tiles, Faulty Render or Motor chimney area or Lead flashing. The Chimney has been removed from room and sealed from the top. But no Air Bricks are on this Shared Chimney. But still getting this mark. One Roofer did say it might be condensation as the back room is small and not used. So Back wall is pretty cold and they Adviced me to get the Sealed Vents Open. Will give it a Try as we and many builders seem to be at a loss to know wht could be causing this damage.. After that will look at outer wall Pebble dash render.. Once again Thank you for your advice.

    sam

    Friday, November 28th

  • Dave Metcalfe

    Hi Peter

    I have 2 unused chimneys which have been blocked off and have ventilation grilles in place. The problem I have is that the chimney pots don’t have cowls so that when its windy there is a significant draught into each room and its also quite noisy. I will probably get the chimney looked at at somepoint, but in the meantime I was thinking about putting some fibreglass loft insulation behind each grille. I was hoping this woild reduce the cold draughts when windy but also allow enough ventilation to avoid condensation. Is this likely to give me problems?

    I would really appreciate your opinion.

    Many thanks

    Dave

    Friday, December 19th

  • peterfall

    Dave
    If you part block the flue with insulation quilt it will reduce the effectiveness of the ventilation. You need to get the air to rise up the flue rather than be blown down. There are a number of patent flue terminals designed to combat ‘down draughts’. Try one of these.
    Peter Fall

    Saturday, January 3rd

  • Ben

    I have an older property that has an internally (beneath the roof) capped chimney in a back bedroom. Any heavy rain results in major damp patches all over the chimney breast (plastered over)

    I should add that it’s currently not inhabited as it’s a rental property with no current tenants so no heating is being used. Would a vent be suitable and if so internal or external? If not, what would you suggest?

    Regards

    Tuesday, January 13th

  • peterfall

    Ben
    As with most queries I receive through the web it is not possible to be definitive over questions such as this.
    You are saying the chimney has been removed on its external section but it still becomes damp with patches all over the chimney breast at times of heavy rain but not whether the damp dries out again, so it is short term? You also say it is an older property but not how old or whether the flue was ever used for coal fires. You don’t say if the chimney is on an outside wall or an internal wall and if the wall is brickwork, stonework, blockwork etc. Each of these make a difference together with the buildings exposure to rain and whether the heavy rain is vertical or driving rain.
    What I can say is the vent is unlikely to be of any benefit as we fit them to keep the inside of soot affected flues dry, so that the soot salts don’t emulsify with dampness in the flue and migrate to the face of the wall. Once they have migrated, the benefit of the vent is no more, instead you must treat the external face of the brickwork beneath the plaster. Because of all the above questions I can’t say if your dampness is from the salts or another cause altogether.
    Sorry about this but I recommend you have the damp patches inspected by a local Chartered Building Surveyor as they will be able to take all of the possible causes into account and give you advice on repairs.
    Peter Fall

    Wednesday, January 14th

  • Dave Metcalfe

    Hi Peter

    Thank you for your response to my earlier question (19th Dec).

    I got someone to cap the unused chimney pots this week in the hope that this would stop the noise and the draughts. Unfortunately it doesn’t seem to have worked! The guy who fitted them is going to come back and take a second look but I’m not confident he’ll be able to sort them out.

    Should a cap (slightly vented to avoid damp) do the trick in this situation or is there something I could try?

    I’d really appreciate your thoughts on this again.

    Many thanks,

    Dave

    Friday, January 30th

  • Peter Fall

    Dave
    Just capping isn’t the answer. You need a terminal designed to combat down draughts.
    Peter Fall

    Monday, February 2nd

  • Sarah Adam

    Hi Peter,

    We live in a semi-detached house built in 1958 which sounds like your typical example (2 reception rooms, both with chimney breasts and a central chimney stack combining chimney’s for both houses). We are currently renovating the house and the original dining room will become a kitchen with the old fireplace covered over. Units will be fitted in front of it with the hob and extractor hood against the chimney. The hood will be vented out using the old flue. We have been advised to brick up the fireplace to prevent smells and draughts and I wanted to ask if this would pose any problems. If the hood is vented out thus allowing air to circulate in the chimney is an air brick still required? The hood will be 2/3 of the way up the wall therefore there would be no circulation of air from the bricked up section to the hood but if we fit an air brick lower down it would be blocked by kitchen units.
    I have read about chimney balloons which allow for ventilation but they need replaced after 5 years and we would have no access to replace it after the kitchen is fitted. Can you suggest the best way of doing this?
    Many thanks
    Sarah

    Wednesday, February 4th

  • peterfall

    Sarah
    I’m not sure about the hood venting out using the old flue. If the hood has a separate duct running from the hood to the chimney pot then ok but if the hood simply discharges its fumes straight into the old flue then definitely not. The thing we worry about with redundant flues is moisture getting into the flue and reacting with the old soot deposits that are embedded in the flue lining. Your cooker hood will be extracting steam from cooking into the flue so you can see that is the worst scenario. If on the other hand you are fitting a duct vertically up the flue then the moisture will not mix with the old soot deposits. If you are ducting the air from the hood to the chimney pot then put a vent into the flue ideally from the side of the chimney breast to avoid the steam from the cooking but still keep the air around the duct dry.
    Personally I don’t think its a good idea to run the duct all the way from the hood to the chimney pot as you will find over that distance the steam will condense in the flue and run back down the duct into the kitchen. I think its better to run it with a slight upward slope across the kitchen directly to the outside. This may not be feasible but the warmth of the kitchen will keep the duct warm and the steam should mostly be extracted and not condense inside the duct. Beware of using fexible ducting that can sag because you will quickly find this fills up with water in the sag.
    Peter Fall

    Monday, February 9th

  • Sarah Adam

    Thanks for the information Peter. I understand the hood we have purhased can either be ducted out or recirculated. If we fit it as a recirculating hood and do not use the chimney should we just cap off the top of the chimney and brick up the bottom including an air brick?

    Monday, February 9th

  • peterfall

    Sarah
    Don’t cap off the chimney, fit a ‘gas terminal’ which will stop water and birds dropping down the flue but still allow the air from the kitchen vent to get out at the top.
    Peter Fall

    Monday, February 9th

  • Sarah Adam

    Thanks Peter. We will get someone in to do what is necessary with the chimney pot. This might seem like a stupid question but are the 2 chimney pots on this side generally for this house?

    Monday, February 9th

  • peterfall

    Sarah
    Each fireplace has a totally separate flue and chimney pot so if you had two fireplaces then you will have two chimney pots. A flue should never be shared between fireplaces.
    Peter Fall

    Tuesday, February 10th

  • Phil

    Hi Peter,
    I’ll try and paint the picture as best as I can. We moved in to a 3 storey Victorian house about 4 years ago, and when I started to decorate one of the 1st floor bedrooms, I noticed that above the fireplace, the nails that the previous owner had left in the wall were all rusty. Then during the winter months, we noticed that there were visible wet patches above the fireplace and had to buy a dehumidifier to clear it.
    This wall is an external wall and the chimney breast for this fire only starts in this bedroom and then goes up to the roof, where it looks like it once extended out through the roof, but has now been taken down and it’s now beneath the roof, plus there is no air vent on the breast. The top of the chimney has been capped under the roof space, so there is no air flow, even with that little flap open on the fire, but we can’t leave this open as soot drops onto our cream carpet!!
    The fireplace itself is for aesthetic purposes only, as it’s the original fireplace, the chimney has probably never used for many many years.
    I’ve had a few builders around and they’ve come up with some strange solutions to this problem, one said to drill a 4″ hole in the corner of the bedroom wall with a diamond core bit right through the double wall to the outside and that would cure it. I asked him that surely we need an airflow up the chimney rather that all the warm air going straight out of the wall, sure enough he didn’t get the job!!
    I’m thinking that I need an internal vent above the fireplace and an external vent at the top of the stack near the roof, this would allow the warm flow of air up the chimney and stop the warm stagnant air from condensating inside the stack
    Regards
    Phil

    Thursday, February 19th

  • peterfall

    Phil
    I fear it may be too late to fit the air brick. This should have been done when the fireplace was originally blocked off and the flue capped or removed. The salts from the soot have migrated from inside the flue to the face of the wall carried by moisture your vents would have dried out in the flue. These salts are hygroscopic and will absorb moiture from the atmosphere in your room showing up as a damp patch. You now need to remove the salt affected plaster and put a barrier on the brickwork of the chimney breast. You need to coat the brickwork with a sulphate resisting primer then apply a sulphate resisting render to the wall before replastering. Do a bigger area than gets damp now in case those areas are also affected.
    Peter Fall

    Thursday, February 19th

  • Gareth

    Peter, Great article and very informative.
    Unfortunately the builder had read it when doing our work and now we have a small damp patch on the inside of our bedroom on the chimney breast. Will installing an airbrick or vent now allow dry the damp to dry out or do you think or would I need to get some other work done to remove the damp.
    Thanks in advance
    Gareth

    Thursday, February 19th

  • peterfall

    Gareth
    Please see the response I’ve just given to Phil below. The same applies I’m sorry to say.
    Peter Fall

    Thursday, February 19th

  • Phil

    Peter,
    Thanks for the prompt reply!! Once the work is done, will I still need to fit the air bricks or will the barrier and rendering you mention stop it completely?
    Kind regards
    Phil

    Thursday, February 19th

  • peterfall

    Phil
    It’s difficult for me to say without seeing the property and the problem but if you are still liable to have dampness getting into the flue then yes put a vent in top and bottom. Safety first says yes vent the flue.
    Peter Fall

    Thursday, February 19th

  • James

    Hi peter,
    I am planning to change a gas fire to an electric fire in a semi detached house. From what I understand I will need to brick up the fireplace behind where the electric Fire will be. Will a singular ventilation brick be typically suffice even if it sits behind the electric Fire. There is no damp currently but obviously don’t want damp being a problem in the future many thanks. James

    Tuesday, March 3rd

  • peterfall

    James
    The answer is a question I’m afraid.
    Was the fireplace ever used for a coal or coke fire? If so then a vent is required, ideally at the bottom of the bricked up opening and this should be some 150x225mm.
    If the answer is no, you don’t need a vent.
    The vent is to stop the soot from the coal or coke fire absorbing moisture and then producing salts. These salts then migrate through the brick walls of the chimney, inside and outside the house, where they dry out on the surfaces of the chimney breast. As they dry out they leave salt residues in the wall which unfortunately readily absorb moisture from the atmosphere and gives you a damp patch on the wall surface. By ventilating the flue we try to stop the soot becoming wet.I hope this helps.
    Peter Fall

    Thursday, March 5th

  • Chris Lewis

    I have a damp problem with a blocked off fireplace. The damp is in the upstairs bedroom in the corner, checked with a damp meter and it’s reading 33%. I had a builder to have a look and reported that the lead flashing is ok and the chimney mortar is ok, he capped off the chimney took the old pot off and sealed the chimney somehow?

    There is still a damp problem though, so I am suspecting it may be condensation especially because the problem got worse when next door (semi detached) became empty. There are no ventilation air bricks fitted anywhere on the chimney, now that the chimney is capped off is ventilation still required? If so where should these air bricks located?

    Friday, March 13th

  • peterfall

    Chris
    I can’t say what may be the cause of the dampness without seeing it I’m afraid. Certainly condensation mould tends to develop in corners of rooms on cold particularly external walls but this is not the only cause of dampness in an upper room.
    As for ventilating the flue, if the old chimney was used for a coal fire in the past, even distant past then an air brick at the bricked up fireplace and then a vent in the chimney stack is required. The chimney stack vent could be just an air brick through the side of the chimney into the flue if the stack has been blocked off at the top. If the flue hasn’t been used for a coal fire then there is no need for the air bricks.
    Peter Fall

    Friday, March 13th

  • Chris Lewis

    Peter,
    There used to be a coal fire fitted a number of years ago, so this may be a lack of ventilation problem?
    The builder who called out and capped the chimney off with no ventilation doesn’t sound such a good thing to do, perhaps one of those vented type chimney pots would have been more suitable instead?

    If an air brick is fitted at the base of the chimney stack (ground floor where the fireplace was originally fitted) and a vented chimney pot fitted instead would this suffice for the ventilation problem?

    Monday, March 16th

  • peterfall

    Chris
    That would be a correct way to ventilate the redundant flue.
    Peter

    Monday, March 16th

  • Ian

    Hi,

    Great article and sorry if this has already been asked, but we are planning to cap our chimneys but leave the original fire places alone – too nice to brick up, but the heat loss and draft is not pleasant!

    Would we need to be concerned about damp? We intend to use a C Cap, they look to allow ventilation at the top of the chimney, combined with the open fire place at the bottom, I would hope this is sufficient?

    Thanks
    Ian

    Tuesday, June 2nd

  • peterfall

    Ian
    By keeping warm air rising up through the flue you will keep the soot deposits dry and prevent their salts from migrating through the chimney to the face inside the house so using a C Cap cowl and leaving the flue open at the bottom should do the job. Always assuming the salts haven’t migrated through the bricks/stonework already and that is unlikely if the flues have always been open.
    Peter Fall

    Wednesday, June 3rd

  • Catherine

    Hi Peter
    I live in a 1900 mid terrace house and the downstairs fireplace has been rebuilt with the flue dropping directly down and pieces of wood stuffed up by previous owners (which I wasn’t happy with). The chimney top is open with no pot.
    A chimney sweep visited yesterday, removed wood and swept it and will return to seal the bottom. At the moment it just sealed with plastic as the whole flue is now open.
    Ultimately I don’t want a fire or stove, happy to keep it empty, but I want it to be sealed and no debris falling out (or insects which I had recently!).
    How do you recommend I seal the bottom / top? I understand it has to be ventilated, but how can this be done but still keeping debris out?
    Thank you.

    Saturday, June 6th

  • peterfall

    Catherine
    I’m sorry but I would not be able to advise you without seeing the property. If you are in the North East of England then give me your address and I’ll quote a fee. If not then you could try the rics.org website and in their find a surveyor section look for a chartered building surveyor in your area.
    Peter Fall

    Saturday, June 6th

  • Catherine

    Thanks Peter, I understand.
    On a similar note, would you recommend a chimney balloon for an open flue? Or would this prevent ventilation?

    Saturday, June 6th

  • Peter Fall

    Catherine
    If you mean a wire basket set onto the top of the chimney pot then that would be fine.
    Peter Fall

    Monday, June 22nd

  • Jonathan

    I have recently found moisture within the chimney cavities which have been sealed top and bottom for 20 years plus I guess. If I install a spinning cowl top to the chimney pots would this increase upward ventilation from 225×225 air brick about 1mtr from the ground fitted in the external brickwork? The chimneys will not be used for any appliance. I have trickle vents fitted to windows for room ventilation.

    Wednesday, July 22nd

  • peterfall

    Yes the spinning cowl should draw air up the flue from the air brick and keep the moisture within the flue at bay.
    Peter Fall

    Wednesday, July 22nd

  • Jonathan

    Thank you Peter

    Monday, July 27th

  • Jo

    Hi Peter
    I’d be grateful for your advice on this. We had our Victorian lower ground floor flat damp-proofed (plaster off, injected, plaster back on) about 3 years ago, by a FMB registered company. We have one bricked up fireplace which was not previously vented, and was not vented whilst the company did their work. I’m now wondering if we should install a vent or not. Whether in doing so, it would affect the damp proofing on this wall?
    Thanks in advance
    Jo

    Monday, August 10th

  • peterfall

    Jo
    I’m the wrong person to ask. Presumably the damp proofing has a guarantee from the FMB company so it is essential you don’t do anything to void the guarantee. Go back to them and ask the same question.
    None the less it is always good to put in an airbrick to vent the flue, even if you install it above the damp proofing plasterwork.
    Peter Fall

    Wednesday, August 12th

  • Jo

    Thanks for your advice Peter,
    Jo

    Sunday, August 16th

  • Dale

    Hi Peter,

    I have just removed a flues gas fire in my 1996 detached house (only ever gas fire fitted) with a clueless fire. I want to board over the hole at the bottom, would it be sufficient to cover the external hole with a slab mortared into position?

    To mitigate draft I planned on putting loft insulation at the bottom before a few breeze block and then plaster board

    With age etc I am told I don’t need to ventilate if sealing both ends?

    Tuesday, August 25th

  • peterfall

    Dale
    If the flue hasn’t had a coal fuel through it then I don’t think you need to ventilate it if you stop using it.
    Peter Fall

    Wednesday, August 26th

  • Gemma

    Hi Peter,

    We want to remove our old gas fire and surround and add an electric stove effect fire which will sit inside the chimney breast. What will we need to do to the chimney breast itself to protect it and stop drafts?

    Thank you for your help.
    Gemma

    Saturday, September 12th

  • peterfall

    Gemma
    I’m sorry but without seeing the chimney breast I cannot say what to do.
    Peter Fall

    Wednesday, September 16th

  • Ashley

    Hi Peter,
    We have an old, unused fireplace opening on the lower level of a two story house (1940s). The chimney is a duel one (on an exterior wall), and the 2nd story fireplace has a wood stove with a liner in it that is used all winter. We want to block off the first story fireplace opening (in a bedroom) by putting ridged foam insulation over the brick and then framing a wall and dry walling over top of the insulation. Eventually, there may be an electric insert installed by opening the wall back up again. The flue of this chimney is currently completely sealed at the top and the flues are both separate. Is this adequate or do we need to add ventilation as well?

    Thank you for your help
    Ashley

    Sunday, September 20th

  • peterfall

    The need for ventilation depends on whether the flue was previously used by a coal fire. Being 1940’s I suspect it was.
    On that basis you need to stop moisture building up in the flue and reacting with salts from the soot. It’s these salts that do the damage. By venting the flue the airflow from inside the house to the outside reduces the moisture and prevents the reaction. My advice is to fit an air brick at the previous opening and reopen the flue at the top, fitting a gas cowl that stops water dripping in but allows the air out.
    Peter Fall

    Friday, September 25th

  • Tom

    Hi Peter

    I have just recently purchased a newly renovated mid terrace cottage that was built in the early 1900s. We have two chimneys which the builder blocked up and stuck internal vents on. The chimneys are located on the party walls between me and my neighbour’s property. After being here for a month or so, damp patches, bubbling paint etc. has started appearing just above the skirting on both the chimney in the kitchen and lounge.

    I have since removed the vents on the chimneys to investigate the source problem to find that the builder has left about a foot of rubble inside the blocked up stacks. Also this rubble is now covered with damp soot. I have spoken to the builder and he has admitted he never got the chimneys swept before closing them up. The chimney on top seems to be capped off correctly and there is good air ventilation coming through the chimneys but I think after seeing the soot covered rubble inside the bottom, I think that maybe some condensation has caused some soot to drop and creating the damp issue.

    My course of action was going to be to create a bigger opening on the stacks, remove all rubble and excess soot, have the chimneys properly swept and then block up the opening, leaving the vent in place. After reading further up this article about salt transfers etc. is there anything else you would suggest?

    Any help would be great!
    Many Thanks,
    Tom.

    Sunday, September 27th

  • peterfall

    Tom
    I can’t really advise without seeing the dampness and bubbling paint.
    What you suggest is all good stuff but you can’t discount rising damp. A cottage of this age probably doesn’t have a dpc unless one has been recently installed. Chimney breasts extend down into the ground so dampness can rise up through the lower walling to appear above the skirting boards. If a dpc has been installed and the work is guaranteed then it could be worth having the dpc contractor re-inspecting incase that is a source.
    Peter Fall

    Wednesday, September 30th

  • Andy Scott

    Hi Peter, I moved into my house 13 yrs ago and the bedroom had a fireplace which I removed and blocked up.
    Through the winters a small amount of condensation formed on the window but nothing to worry about.
    18 months ago we had cavity wall insulation and now have major condensation with mould on the walls around the window frame.Leaving the window on vent ot leaving the heating on all night makes no difference.
    I was thinking of putting a vent in the top part of the chimney breast just below the ceiling, is this a good idea?

    Many thanks

    Andy

    Saturday, November 7th

  • peterfall

    Andy
    I’m afraid I don’t. I appreciate you want to get rid of the high levels of humidity in the room but putting it into a flue that previously served a coal fire could give problems of salt migration through the stack.
    I don’t know your house so it would be wrong of me to give you advice about the mould growth but it sounds like a cold bridge at the window opening. I suggest you have the insulation installer back to comment or get a local chartered building surveyor to inspect the area and give independent advice.
    Peter

    Monday, November 9th

  • Barrie Stewart

    Hi Peter, I’m experiencing a damp area appearing on an external wall and chimney on my house. The chimney is unused, has an air brick at the bottom and a cap on the top. For the last couple of years I’ve noticed a damp patch appearing on the outside of the house in the winter. I’ve had various people (roofers , chimney sweeps etc) look at it and they’ve each tried different things. (tidying up pointing, pulling out an old flue liner etc) but the damp patch has just returned over the last few weeks. I knocked the centre out of the air brick and managed to remove a load of soot, some of which was wet. I recently bought a set of drainage rods and fed them in through the air brick and managed to get them all the way to the top of the chimney cap so I’m pretty sure there’s an airflow through the chimney now. I was thinking that the soot in the chimney was restricting the air flow and leading to condensation inside the chimney which was then causing the damp area to appear on the roughcast. Now that the chimney is clear (its not been swept as yet but I plan on having it done) the damp patch is still visable. Is this likely to be due to the wet soot creating salt which has migrated through the roughcast? If so, whats the best way to get the wall to dry out? Remove all affected roughcast and then re-roughcast the wall?

    Saturday, November 7th

  • peterfall

    Barrie
    It sounds like the salts have migrated through to the outer face of the wall. This is not unusual with older houses. I’m afraid the only solution is to remove the render and treat the wall before reapplying the render. Do this after you ahve cleared the flue say next summer.
    Peter Fall

    Monday, November 9th

  • James E

    Hello Peter,

    Thanks for the article and advice. We have a 1930s detached property. A couple of years ago we replaced an open fire on the ground floor with a gas fire but left the chimney flue redundant and the chimney stack in place open on the roof. On the 1st floor in the room directly above the ground floor there have been a series of damp patches in exactly the same place on the wall just below the ceiling line. There is no chimney breast in the room but the damp patches line up with the redundant chimney. The symptoms have persisted over the years. We have removed the chimney stack and put in ventilation tiles on the roof where the stack used to be. Inserted 2 air bricks at the top redundant chimney breast and a further airbrick half way down level with the first floor to create an airflow from one airbrick to the other. The problem still remains. A roofer has suggested an internal air vent inside the room as well as having two external air bricks as well?

    From your advice on here “Salts embedded in the stack will cause staining at high level on the stack. On large roofs with the stack at the ridge the staining occurs in the roof space. Where the roof is very shallow or the stack is at the eaves then the staining can extend down to the ceiling of the room beneath. To overcome it you need to remove the affected plaster, seal the wall with sulphate resisting primer and the apply a sulphate resisting render to the wall, finishing with plaster.
    Ventilating the flue will prevent the salts from migrating to the face of the stack but once they are embedded no amount of ventilation to then flue will remove them.”

    Could I ask what the next steps are to take are:
    1) Surveyor?
    2) Insert internal air vent to improve air circulation?
    3) An additional air vent at bottom of chimney breast (but above gas flue outlet)?
    4) Get builder in to remove the affected plaster, seal the wall with sulphate resisting primer and the apply a sulphate resisting render to the wall, finishing with plaster.

    Any advice greatly appreciated.

    Many thanks
    James

    Monday, November 9th

  • peterfall

    James
    It sounds like it could be the salts migrating from the redundant flue. If that is the case then option 4 is the way forward but I think option 1 would be a good idea as a starter, just to check the construction of the house, comment further on the flue ventilation and agree it is a salts problem.
    Peter Fall

    Monday, November 9th

  • Hannah

    Hi Peter,

    I have found your article really interesting and useful.
    We, like many others, are blocking up our fireplace. We have currently removed from the wall and simply have a board up at the moment to reduce drafts.
    We have a plasterer coming in next week (W/C18th Jan) to skim over the wall, however we do want to check on what works we need to do prior to this. We understand there is a requirement for a vent internally (low level), would an air brick be required in opposite on the outside of the external chimney breast too?
    We also have a vent within the room which sits approx. 1m to the left of the old fireplace. If we were to have a vent fitted in the fireplace location, do you know if we could then block up the other to avoid having two? Is there also a recommended size?
    We are looking to get a cap fitted to the top of the chimney outside.

    Any help and advise would be much appreciated.

    Regards
    Hannah

    Wednesday, January 13th

  • peterfall

    Hannah
    Like many of the queries I receive to the website I have difficulty fully appreciating the problem and therefore suggesting an answer. An inspection would overcome this dilemma.
    The important point is to get a flow of warm drier air to rise through the now redundant flue, up and out at the top. Hence the need for an air brick at the bottom and an outlet at the top. I appreciate that an air brick on the face of the chimney breast in the room is not attractive therefore an airbrick broken in from the side at low level would do just as good and it would be less obvious. You don’t need an airbrick venting at low level externally and indeed I could argue that introducing external cold air would not be as effective as using the warmer internal air.
    At the top don’t cap off the flue but either leave the original pot in position or if you are worried about birds and water getting into the flue then fit a standard metal gas cowl to allow air out but prevent water and birds getting in.
    I’m not sure what your present vent is for set 1m to the left of the fireplace. If it is into the chimney breast and this room and fireplace is at first floor level then it may be venting the flue from a redundant ground floor fireplace. If it’s just through the gable wall to the outside and it is set above floor level then it is probably only to ventilate the room. Sorry that I can’t help with that.
    Peter Fall

    Wednesday, January 13th

  • Alex

    Hi Peter.
    I’ve tried to read as many comments as possible to see if there’s one that fits my question but there are so many. Anyway my house (c1860 ish) has had its chimney removed so now there are four square holes at floor height in my loft (like a slice of battenburg cake), all fireplaces also blocked off. From what I can see 2 of the 4 chimneys are 1/2 to 3/4 full of rubble, the third I would guess has 1.5 metres of rubble, the fourth – cannot see – has a redundant water immersion on it.

    So while there does not seem to be any damp areas I can see (I feel it could be drier) I would still like to put in vents at the bottom of these chimneys – but is there any point if filled with rubble I cannot remove – or best to just properly cap off the tops? (obviously I would get a builders advice before any work but would like to hear yours too before I decide, thanks Alex

    Thursday, January 21st

  • Alex

    Hi again, sorry I should probaby say the ‘quad’ of chimney stacks is in the centre of the house so no outside/external walls involved, thanks Alex

    Thursday, January 21st

  • peterfall

    Alex
    I can’t give you direct advice without seeing the property but I haven’t seen a chimney breast dampness and salt staining problem on an internal stack that for a number of years, has been reduced to below the roof level. Redundant stacks are vulnerable to rainwater soaking down from the outside chimney stack or in from the exposed gable wall. If the outside stack has been removed to below the roof level and the chimney is fully internal then the sources of dampness are limited to pipe leaks and condensation. I would expect the risk in your instance to be low with no need for ventialation. But I need to see the building before I can confirm this.
    Peter Fall

    Thursday, January 21st

  • Alex

    Hi, Thanks for replying so fast Peter. The building was an old bakery and then was a shop for many years until 5 years ago. we only bought the property 5 months ago so we are just trying to get to grips with the whole place.

    Thursday, January 21st

  • Richard

    Hi Peter,
    I have damp spots which have appeared on the ceilings of two rooms immediately above old sealed 1st floor bedroom fireplaces.
    The house was built in 1949 and about 15 years ago a builder took down the 2 old chimney stacks flush to “ceiling level” and tiled the roof over the stacks. I note we haven’t any air bricks in the stacks and having inspected the roof cavity can’t see any obvious problems from water seeping through the tiles/membrane.
    All 4 previous fireplaces have been sealed with no apparent ventilation.
    Can you advise please – Is the lack of ventilation likely to be the cause of the damp and how might i treat this
    Thanks in anticipation

    Wednesday, February 10th

  • peterfall

    Richard
    This is a difficult one for me to answer without seeing the house. Dampness stains can occurr on the ceiling adjacent to a chimney breast but usually as an extension of the dampness on the breast itself. None the less it is always a good idea to ventilate a redundant flue with an air vent at the base and either leaving the top open or capping the top and fitting a vent into the flue at the side.
    I’m sorry I can’t be more specific on this one.
    Peter Fall

    Thursday, February 11th

  • Francis

    Hi Peter

    I’ve just bought a property with four Chimneys. None of the chimneys are being used . The chimneys all have cowls on them. Do you think it’s a good idea that I get them cleaned or should it not matter if they’re never going to be used again? Will there be an impending issue with damp being left as they are? I’m not going to block them off inside the property as I see them as a feature. Your advice will be greatly appreciated.

    Sunday, February 14th

  • peterfall

    Francis
    If you are intending to leave the flues open at the top and bottom than I suggest you have them swept as there could be loose mortar and soot which may start to drop down the flue and onto the hearth and spoil you floor coverings.
    The open flueways should keep any damp from salts at bay.
    Peter Fall

    Monday, February 15th

  • April

    Hello Peter – hope you can help with a little advice. In an upstairs bedroom, the chimney breast is showing brownish staining at the top near ceiling. Directly above this area is a lead covered flat valley between 2 roofs. The fireplace is open in the bedroom (but not used) and below in the kitchen the old fireplace is blocked up. Also on the other side of the chimney breast is the master bedroom wall also showing an historic damp patch which does not change in size at all and does not show any brown staining. The house is Victorian. We have had several roofers attempt to solve the problem by replacing roof tiles, repointing the chimney, checking the flashing, etc. The brown stain appeared after heavy rain and other small areas are appearing too.
    Would it be a good idea to light a fire regularly in the bedroom fireplace to dry out the inside of the chimney? I really wish I could have a good look at the valley and chimney flashing where it meets the roof myself but its too high to go up a normal ladder so would need scaffolding.

    Monday, February 15th

  • peterfall

    April
    It’s always difficult to diagnose a problem without seeing it first hand so I’ll restrict myself to general advice based on assumptions.
    From what you say the chimney stack passes through a valley gutter between two roof slopes so I presume there is only a short vertical distance between the ceiling level and the exposed bricks of the chimney stack. I also presume the flues were used by coal burning fires a long time ago.
    The flues are completely separate from each other therefore the ventilation going up the bedroom flue will not dry out the blocked off kitchen or master bedroom flues so lighting a fire in the bedroom will have no effect on the other flues.
    If there are no defects in the valley gutter or the flashings to the stack then it is more than likely the water is draining down through the brickwork of the chimney stack. Current Building Regulations require a damp proof course to be built into the chimney stack at the flashing level but your Victorian stack won’t have one so there is nothing stopping the damp percolating down through the bricks. This, once it mixes with the soot deposits around the flueway, becomes a salt that absorbs moisture in the atmosphere. Heavy rain also means heavy humidity in the atmosphere so the salts absorb this moisture and it looks like a damp patch on the plasterwork.
    The solution isn’t cheap. You need to dismantle the stack down to the flashing level and insert a lead damp proof course. You then need to treat the salts that are in the wall and plasterwork around the chimney breasts.
    I hope this helps.
    Peter Fall

    Monday, February 15th

  • John

    Hi Peter – what a great service!

    I have recently moved into a 1930’s house with a (holed) brick and black mortar built chimney stack. Both fire places upstairs and downstairs have been blocked off with no ventilation. Two of the bedrooms have very damp walls and it’s been getting progressively worse. I can tell that poor attempts have been made to cure the problem previously (4″ vents in the room at ceiling height!!), plaster upon plaster and mastic on the chimney stack.

    So far I have replaced the lead flashing, today removed the last pot (3 of which were open to the elements) and reduced the height of the stack as it was a bit ropey, and re-pointed the remaining stack.

    I have also removed the horrid black render internally, back to brickwork, so now I can see the water coming from above. I believe that it has been running down the inside of the stack and seeping through the mortar.
    We have no intention of using the chimneys again (or for a long time) and I’m happy to cap them off, so here’s my quandary….
    Do I
    1 fit vents into each of the rooms and cap the stacks off (allowing air to flow)?
    2 cap them off so that they are airtight top and bottom?
    3 fill them with vermiculite?

    Thank you

    Monday, March 14th

  • peterfall

    John
    This chimney doesn’t sound to be in a good state. I would be tempted to take the stack down completely to below roof level and roof over but if you want to keep the appearance of the stack then rebuild it with a lead damp proof course across the brickwork at the top level of the flashings to stop water migrating down into the building.
    That deals with the stack but not the dampness on the walls. If the dampness is to the chimney breasts then you will need to hack off the damp affected plasterwork apply a sulfate resisting primer to the brickwork, and then replaster with a sulfate resisting plaster as a base coat. If you can afford the time of say a year then leave the old affected plaster in position after rebuilding the stack so the wall starts to dry out and the salts migrate into the present plaster finish before you hack it off and replace it.
    If the damp isn’t on the chimney breast wall then it is probably from another source altogether and that will need a full investigation.
    Peter Fall

    Monday, March 14th

  • john

    Thanks Peter. I would take them down but I can’t find any similar roofing tiles anywhere. If I cap the stacks where I’ve reduced them at a height of 4 courses above the flashing, should I replace the pot and cover it with a rain guard to encourage circulation and drying-out; or can I completely seal the stack?
    John

    Tuesday, March 15th

  • peterfall

    John
    We are venturing into the area where an inspection is required I’m afraid. taking the stack down to the flashings, then rebuilding with a dpc will stop water soaking down the stack. The problem you may have however is the salts that could have migrated from the flue through the bricks and into the plasterwork. If that is the cause of the damp on your bedroom chimney breast then no amount of ventilation will help, it’s too late I’m afraid.
    My problem is I can’t see the dampness, the position of the flue and the chimney breast so I can’t give you good advice. Sorry
    Peter Fall

    Tuesday, March 15th

  • Michelle

    Hi Peter

    I have come across your website as we are trying to fix a damp patch that has appeared after the recent storms in one of our bedrooms. We live in a semi detached victorian property and discovered that this bedroom with the damp has had the chimney stack totally removed. So the chimney ends in our loft! Next door still have theirs in tact. We are concerned as have been told the chimney stack is not properly supported on our side where it has been fully removed internally but not supported properly in our loft. Since the storms also, I ‘think’ water has just leaked into the chimney through the open pots and straight onto the ceiling of the bedroom. How on earth would we sort this problem out? We have no idea who to ask and we want it done properly-no Cowboys. Do we approach a roofer or a structural engineer or both?? The way I see it we have two problems-the unsupported stack and the water leaking straight into the loft and thus the bedroom ceiling. I appreciate without seeing you may only be able to speculate but I would hugely appreciate any advice you could offer up. Thank you in advance.

    Wednesday, March 16th

  • peterfall

    Michelle
    I suggest you ask your local Chartered Building Surveyor to come out and inspect the building. If you don’t know one then try the rics.org website and use their Find a Surveying Firm section but make sure you specify a building surveyor and then review the firm’s website to check that they do specific defect inspections as not all of them do.
    Peter Fall

    Wednesday, March 16th

  • Michelle

    Thanks Peter. So would a building surveyor be able to let us know who we would need to employ to rectify the situation and potentially how? Thanks, Michelle

    Tuesday, March 22nd

  • peterfall

    Yes they should be able to recommend a remedy and suggest competent contractors.
    Peter Fall

    Wednesday, March 23rd

  • Mario

    Hello Peter:

    I have a victorian 3 bed – typical 2 front reception rooms both with Fire places both working.

    In one their is damp on the side and front of the chimney breast just above skirting level. Sometimes its actually wet and you can see the water. Only above skiting , and not much higher up, maybe 6 – 12inches high.

    The house has been re pointed in the last 18 months. Their is an air brick, and i had a builder dig along the outside of the house to create gap, the previous owner had covered the air brick with a patio, But this has all been done over the past 2 years. If we light the fire, after a few days it does dry out, stop the fire it soon comes back.

    There is a damp course , it look like slate.

    The previous owner was a proper developer, and the patio is around 4 – 6 inches higher than the lawn, and as i said it was covering the air brick.

    Any ideas ? on builder has said he would need to come inside and dig the floor up to find out the problem, which sounded expensive and messy.

    Any help would be greatly appreciated.

    Thursday, March 24th

  • peterfall

    Mario
    I’m sorry but there are too many possible causes for this problem for me to pontificate on the actual cause here. It needs an inspection by someone who deals in this type of problem rather than just your local builder. Can I suggest you ask a specialist dpc contractor to look at the damp patch. I use Peter Cox Ltd. but there are others about.
    Peter Fall

    Monday, March 28th

  • David Byars

    I live in a stone and brick built Victorian top (second) floor flat in Edinburgh, and effectively live in the mansard style roof. The terraced houses were built around 1890, and have each been converted into three flats.

    There are four chimney stacks adjoining our building, two on either side, which are shared between us in our building, and the adjoining neighbours.

    Therefore, these four stacks (25 pots in total) cover 9 flats.

    I understand that all rooms in Victorian properties would have once had a fireplace. There are probably four main rooms in each flat (living room, two bedrooms & kitchen), meaning that there would once have been 12 fireplaces in our building, and perhaps 6 fireplaces in each of the adjoining buildings sharing our chimney stacks. This equates to 24 fireplaces (there are apparently 25 pots) – perhaps the ground floor flat once had 5 fireplaces?

    The old roof sprung a leak and needed to be replaced. Damage was caused to one of the exterior walls next to one of the dormers. An area of plasterboard and corresponding plaster was removed and replaced, and timbers treated. The work was carried out by a roofing & building company (who hired plasterers), but with no involvement of a preservation company – I’m hoping the timbers should be okay?

    In the past there has also been water ingress into the kitchen due to a flue for a gas boiler not being properly sealed at the roof (on getting GCH installed).

    About 18 months after getting the roof replaced I decided it would be a good idea to get some surveyor to check my flat given the prior issues with the roof and the gas boiler flue.

    I got a surveyor from Wise Property Care to inspect my flat. I wanted to ensure that there was no outstanding damage, but I wasn’t expecting there to be any current, ongoing areas of dampness.

    It turned out that moisture meter readings combined with a visual inspection indicate a water ingress issue both to the living room wall and above the kitchen wall units in the areas where chimneys are located.

    The surveyor suspects that dampness may be filtering in through a possible defective seal around the chimney and this has resulted in the dampness noted to the wall plaster. They recommend a roofing specialist inspect all areas of the roof and gutters and carry out any works that they deem necessary.

    There are two disused fireplaces in my flat, one in the living room (above which is the first area of dampness) and one in one of the two bedrooms (where apparently there’s no area of dampness, but it may have been here where I once saw an area of stained wallpaper prior to redecoration).

    There are no existing fireplaces in either the second bedroom or the kitchen.

    I’ve since had roofing/chimney specialists inspect the roof and chimneys.

    It appears that the roofing, flashings, chimneys etc. are sound, although some minor work may be required to the stacks.

    One said that the dampness is due to the chimney pots being open, and not covered. I think they said that rainwater is going down the pots in each stack, accumulating, and entering my property.

    Perhaps my top floor neighbours on either side may be equally affected?

    If this is the case, then all my neighbours (including myself) are contributing to this dampness issue?

    Another company said that the problem could be due to inadequate ventilation in my flat. However, I generally leave the interior doors open, especially the bathroom and kitchen doors. The windows (except in the living room bay window) are vented, and, importantly, I have my own dehumidifier (in the hall) running 24/7, targeting a relative humidity of 40%. In addition, the two areas of dampness are around chimney areas.

    A third company (who replaced the roof) has taken a look, but I have not, as yet, had any response from them. They have lent me an industrial dehumidifier to help dry the walls in the living room and kitchen.

    I have read on the internet that dampness associated with chimneys results from one or more of the following:

    – leaks
    – uncovered pots
    – condensation in the flue (lack of ventilation)
    – hygroscopic salts

    None of these roofing/chimney companies seem interested in the possibility of either condensation or hygroscopic salts being a cause.

    I have consulted my neighbours about getting caps on the disused chimneys (the C-Cap looks a good choice), and cowls on the active chimneys (here the Colt Top looks a good choice).

    Should chimneys be cleaned prior to capping?

    I gave a note to all the neighbours explaining that I would like to jointly get the pots covered using these caps/cowls, along with any necessary work needing done to the stacks. The total cost could have been shared between the buildings/stairs 50% / 25% / 25%, with us in our stair sharing 50%.

    Unfortunately, one neighbour on the ground floor in one of the adjoining stairs says that their side of the stacks are in good order, that their roof was replaced very recently, and that they have had no issues in their property since they moved in some 18 years ago. He is of the opinion that each owner should act on their own in order to ascertain the condition of their chimneys (although a stair could agree to act collectively if they so wished).

    There is also the issue of disused chimneys at the bottom of the flue. It appears that the fireplace in my living room has been sealed without any ventilation, and newspapers have been stuffed up inside the flue in the fireplace in the bedroom. I understand that this can cause condensation.

    No doubt some sort of air brick should be fitted in the living room, and something else should be fitted in the bedroom where the fire grate is still present (chimney balloon?).

    In fact, if a fireplace has not been sealed, would a ventilated cap on the chimney pot suffice (e.g. C-Cap) so that the bottom of the chimney could be left open in the bedroom? In other words, would a good quality cap stop enough of the heat loss from a room (as the flue length would be fairly short in a top floor flat)?

    There is also the matter of the fireplaces that have disappeared. The 25 pots in aggregate is likley to be considerably in excess of the current number of fireplaces (used or disused). Have these “disappeared” fireplaces just been bricked up and plastered over? What about ventilation?

    For example, in my kitchen where there is damp, there are probably no vents above the wall units.

    There is the issue, in my mind, of whether any condensation in my neighbours’ chimneys could also be contributing to the dampness in my flat?

    As for hygroscopic salts, I wrote to the preservation company (Wise) about whether this could be a possibility (along with the possibility of condensation), but never got any response.

    I have no idea whether they tested for the presence of these salts, and I am wondering whether I should have someone carry out such a test?

    I realise that I must first solve the source(s) of the damp, but the preservation company has quoted for carrying out the following:

    Plaster and exposure treatments in order to ascertain the condition of the ceiling joists (kitchen) and inspect for any signs of fungal decay (sterilise as appropriate).

    The ceiling boards, wall and ceiling plaster will be renewed (as appropriate).

    Living room:
    remove wall plaster down 1 metre, renew with Limelite renovating plaster

    Kitchen:
    remove damaged section of ceiling, inspect, renew ceiling boards and re-plaster;
    remove wall plaster down to cupboard level, renew with Limelite renovating plaster

    I realise that redecoration will be required afterwards.

    On the other hand, the roofing & building company who replaced our roof, and lent me the industrial dehumidifier, have suggested letting the affected walls dry, and then get a different preservation company to check for dampness.

    I am concerned though about the risk of dry rot etc. if I do not follow the advice of Wise Property Care.

    Thanks for taking the time to read this message.

    I would very much appreciate any advice, and expertise, you can give me as to fixing the problem, and whether I need to do anything more than just let the areas of dampness dry out once the dampness issue has been addressed?

    Should I get several more roofing/chimney companies survey the roof & chimneys, or would it be best to arrange a building surveyor to inspect the problem areas?

    If only you could come up from Newcastle upon Tyne to Edinburgh…! 🙂

    Wednesday, May 11th

  • peterfall

    Wow this is a big question and not something that this blog should be trying to answer, sorry.
    Peter Fall

    Friday, May 20th

  • morris

    Hi Peter.
    We have been having dam patches on the upper floor spare room by the windows and old chimney area. When we got a few people to inspect the damp patches that said it is condensation and we need air vents in the room. We installed Air vents and got the wall re-plastered and the walls were showing a brown/ yellow stains and started to bubble. This was late year. Today the newly plastered walls are still showing the damp patches that have come out.(we did not paint the walls). Got a few more people in to inspect. And many now point to the roof. There is a old Chimney stack which is capped off (cement only on the top) but in the loft space the chimney it totally removed. (does not run down only halfway). We had many roofers saying they cant find a problem with the stack. But one said we needed to have Air vents to the chimney. as this might be causing condensation. My question is even if the chimney is removed totally would this cause a problem of damp on the wall?

    Thanks

    Wednesday, June 8th

  • peterfall

    Morris
    I’m afraid you are asking me an impossible question. In order to answer I would need to visit the property and inspect the affected area.
    Soot salt deposits embedded into the retained wall could be causing the staining but so could water draining down from the top, condensation generated by the occupiers of the building and a number of other causes.
    I’m afraid defect diagnosis isn’t a simple tick sheet but a careful consideration of the many causation factors.
    Sorry.
    Peter Fall

    Thursday, June 30th

  • Neil

    Hi Pete,

    This is a really useful article. I have a chimney breast in a c1900’s Victorian house and the chimney breast is quite damp. It has been blocked off in the bedroom and the breast has been removed in the floor below.There is no staining. I need to open up the old flue that was originally for the downstairs part of the chimney. Can I put an airbrick in the side wall of the chimney instead of the front face as we don’t want a vent in the front.

    Thank you

    Neil

    Wednesday, June 29th

  • peterfall

    Neil
    Yes you can put the vent into the side of the stack as long as it goes into the flue. Make sure that both the upper and lower fireplace flues are vented.
    Peter Fall

    Thursday, June 30th

  • Neil

    Hi Pete,

    Sorry, I forgot to add that the flue is open on the stack.

    Thank you

    Neil

    Wednesday, June 29th

  • Neil

    Hi Pete,

    Thanks for getting back to me. The two flues would-be open as we have a decorative fireplace in the upper flue hence why we don’t want a vent to the front. I know you suggest not to but if I drill a series of 20mm holes in the side and place a vent over them will this work? I’m worried about removing and replacing a brick as the breast has been removed below-c40+ years ago. Not sure how is it supported.

    Thanks again.

    Neil

    Thursday, June 30th

  • peterfall

    Neil
    If the fireplaces are open then you will have enough ventilation up through the fireplace and not need an airbrick. If I’ve misunderstood what you mean by ‘the two flues would be open’ and you are blocking off the flues above the fireplace to stop dirt from dropping down then make sure the side airbricks are set above the line of the blocking off. Also make sure the flues are open at the top so the air can flow up and out.
    Peter Fall

    Friday, July 1st

  • Neil Crooks

    Hi Peter,

    Thank you again. Sorry, I will try and explain a little better. The chimney breast in the kitchen has been removed and it is remaining on the bedroom above all the way to the chimney stack on the roof. The two pots are still open with cowls on top. The chimney breast (fireplace) in the bedroom was blocked off, but I have opened it and put a decorative fireplace in. The flue that would have run from the kitchen is unvented in the bedroom so I wanted to open it to allow airlow. I know it is clear inside as there was a floor mounted boiler in the kitchen when we moved in that had a flue running up to the chimney pot. I want to ventilate the flue that used to run from the kitchen but don’t want to remove a brick to put in an airbrick as I am unsure what is supporting the chimney. I thought that maybe drilling a few large holes into the brickwork might work and want to do this on the side of the breast to stop it being next to the fireplace. Then cover that with a vent cover.

    I hope that is clearer? Thank you again for your help.

    Neil

    Friday, July 1st

  • Matthew Hayhurst

    Hi Pete,

    I have been reading a different website (http://www.telegraph.co.uk/finance/property/advice/10112581/Jeff-Howell-should-we-cap-our-unused-flues.html) and it says there that common practice in a blocked up fireplace is to insert an airbrick at HIGH LEVEL just below ceiling height. I note that you recommend putting the air brick at ground level. Does it matter?

    Also my chimney pots have been capped. The bedroom fireplaces have been boarded up with no vents. Do I need to uncap the chimney pots and replace them with ventilating cowls and then put vents in the boarded up chimney breasts in the bedrooms?

    Thanks
    Matt

    Tuesday, August 9th

  • peterfall

    Matt
    The purpose of the air brick is to ventilate the flue If it is at high level then the section below will not easily ventilate.
    I suggest you use ventilating cowls as this stops water entering the top of the flue.
    Remember it is only necessary to ventilate the flue if it was previously used to burn coal or coke and there isn’t a flue liner in place from a previous gas fire use.
    Peter Fall

    Tuesday, August 9th

  • Matthew Hayhurst

    Thanks Peter.

    Actually my chimney pots are capped with pepperpot caps.

    Am I right in thinking that these will provide adequate ventilation?

    If so I can just block the chimney breast and put in an air brick/vent and I’m good to go?

    Thanks
    Matt

    Thursday, August 11th

  • peterfall

    Sorry I don’t know the term pepperpot caps but if you are saying they let air out but are sheilded from rain entering then yes.
    Peter Fall

    Thursday, August 11th

  • Goran

    Hi Pete,
    3-bed 1938 semi, first floor bedroom. I have removed the (small) fireplace thus gaining more floor space. The cavity is dry and shows a well built brick structure with a neat bricked arch (clean – probably seldom used in the past). I wish to turn it into a small built-in bookcase with a copule of shelves. How do I ventilate this space and yet – protect the books from anything falling down onto them. Do I have to build the cavity ceiling and then cut into to the chimney just above it, for the air brick? Too difficult and costly …anythnig simpler you can think of? Hoping you can advise me so that I can progress with the halted work. My child has decided for the cavity to be the centre piece of her future bedroom! Various designs integrating the unused fireplace are so carefully discussed and drawn as I type … (the fireplace cavity is 50cm wide, 35 cm deep and 80 cm high) … the gaping hole in the wall is waiting for the venting solution … PLEASE 🙂

    Monday, August 15th

  • peterfall

    Goran
    A point that may be in your favour is whether the fireplace and therefore chimney was ever used to burn coal or coke. Many small bedroom firplaces weren’t and only had primitive gas fires fitted. If it was never used to burn coal then there won’t be any soot to worry about and therefore no need to ventilate. It’s the old soot deposits that cause the problem.
    If it was used to burn coal and the inside of the flue is black with soot deposits despite cleaning, then cut a hole above the book shelves and fit a vent into the flue at this point. Make it as low as you can as you will be blocking off the flue at the bottom when you fit the book shelves to prevent soot and mortar droppings falling onto the books.
    Peter Fall

    Thursday, August 18th

  • Goran

    Thank you so much for your quick reply!
    Moving on then … will report in due course.
    Goran Radic

    Friday, August 19th

  • Goran

    Well … the child won. Wanting this to be the centre piece of the room – with all brick work exposed. So … it is going to be a bendy curved marine ply for the fitted bookcase top with venting, sieve like, holes. The “ceiling” curve is mirroring the one of the balck painted metal lintel that supports the exposed brick arch. Inside the chimney a few inches above the bookcase a simple ply shelf (along the “ceiling” vertex) large enough to stop anything falling onto the holes but plenty of space on both sides allowing air to flow freely. All brick mortar raked and re-pointed, white shelves to match white woodwork in the room. Fun to implement!

    Sunday, August 21st

  • Ann

    Hi,

    We have a 4 storey 1850’s Victorian house. I want to use a chimney sheep in one of the unused fireplaces on the second floor. The chimney has no cowl. If the chimney sheep gets wet from rain, would it cause damp issues in the chimney breast?

    Monday, August 22nd

  • peterfall

    Ann
    These devices block air flow up the flue so even if the ‘sweep’ didn’t get wet the soot in the upper flue could and then you will get damp appearing on the upper chimney breast as you don’t have any means of drying the damp soot.
    Peter Fall

    Monday, August 22nd

  • claire

    Hello Peter
    I appreciate it is hard to advise without seeing the issue/property first hand however if you could provide some advice it would be greatly appreciated.
    we have a typical 3 bed semi built in 1951. The chimney is in the centre of the house between the living room (front) and dining room (back of house). The chimney stack continues into the main bedroom above the living room (front of the house), this looks like it has been blocked up for many years or was never open, there are no issues. The bedroom at the back above the dining room is flat so the stack turns towards the living room and up through the front bedroom and continues to the roof. (story, this is the best I can explain).
    We have recently had the old back boiler removed from the dining room chimney breast and have removed a non load bearing wall separating the kitchen and dining room to make the whole space a kitchen. During the building work we have had the roof inspected and the chimney re-pointed, lead flashing re-done etc. The spinning cowl to the chimney flue in question is still in place and has been re-mortered.
    The builder has removed the front side sections of brick from the chimney sides revelling the flue as these were built out with no support for the stack itself. We need this floor space for the new proposed kitchen.
    We need to build a single brick wall in front of the wall that is essentially the back of the living room chimney wall/flue so far up, then as the wall slopes away, this will create a cavity higher up.
    The flues have at some point in the past been used to burn solid fuel, so they need ventilation to keep the soot dry. We have cleaned as much of the soot away as is possible to minimise moisture retention.

    My quandary is. do we install an air brick to the top of the wall we are building to not only level the wall for kitchen units below but still allow the airflow from the top section that will be a chamber so to speak? Is the air brick higher up effect anything? We can’t put it lower down as this essentially will be against a wall!
    Is it acceptable, will it help or indeed hinder the inside of the flue, if we were to paint it with a liquid damp proof such as bitumen paint to try and minimise the moisture on the remnants of soot whilst we still have access?
    The two flues we have are not used, the living room has only a decorative fireplace.
    We plan to keep the spinning cowl on to aid ventilation and leave the old metal flue in place, this has just been cut higher up. Does all this sound ok?
    Once the wall is built and ventilation added, we plan to dot and dab plasterboard to the wall and have it skimmed. I would very much appreciate your time in advising the best action to take to prevent any future problems before the work is carried out.
    many thanks, claire

    Tuesday, September 27th

  • peterfall

    Dear Claire
    This is difficult for me to envisage and therefore help you I’m afraid. Presumably your builder is fitting support for the bottom of the retained section of chimney breast. If you can leave the bottom of the flue open say within the floor void to the first floor the air will be sucked up through the flue by the spinning cowl on the top and do the job.
    Peter Fall

    Wednesday, September 28th

  • Frank

    Dear Peter

    I came across your website and really hope that you may be able to help me. I have read your blog and answers above but none quite fit the bill.
    We live in an old 4 bed sandstone detached house. On one side of the house the chimney had 5 chimney caps (elephants feet or pepper pots depending where you live) – however we could only find 3 rooms with a vent (3 blocked up fireplaces). I assume the 4th fireplace was in the kitchen but was knocked out when the kitchen wall was taken down. No idea about the 5th chimney. None of the chimneys are in use. There was a constant leak into the kitchen which several roofers could not locate. Finally the fireplace above the kitchen was found to be soaking so the leak must have been coming down the chimney. 2 of the caps in the middle were poorly cemented in and once taken off the flues were found to be pretty damp. The roofers slated & cemented over chimney pots 2 and 3 to stop further rain entry. They said that there would be enough ventilation coming from the caps in 1, 4 & 5. Is this correct? From my understanding of chimneys: bed 1 is chimney 1 – room vented and this has a cap
    Room 1 is chimney 2 – room vented and now blocked off at top
    Kitchen is chimney 3 – no fireplace as wall removed and now blocked off at top
    bed 2 is chimney 4 – room vented and this has a cap (this is the fireplace that was found all wet)
    Chimney 5 – no idea of where this flue went but this has a cap

    Basically we are trying to work out if there is sufficient ventilation or whether it will be ok. I am slightly confused by the fact that we don’t know where 2 flues came from!
    Any advice appreciated. Thanks.

    Wednesday, September 28th

  • peterfall

    Frank
    I’m sorry I can’t really say one way or the other for this query. What I can say is each fireplace has its own flue therefore to say that the air passing through one flue will vent another is wrong, it won’t. You need to treat each flue as a separate entity with air coming in at the bottom being sucked out by the air passing over the top of the chimney. This is to keep the inside of the flue dry.
    If the flues are pretty straight up through the house then a vented cap is required to stop rain and snow from dropping down the flue.
    Peter Fall

    Wednesday, September 28th

  • Frank

    Hi Peter

    Many thanks for your reply. If the feathers between the 2nd and 3rd chimney had come down between them (at least a good 150 cm at the top of the flues) could you get away with one chimney being blocked off and the other being vented? Also if the chimney had an old gas fire in is it best to remove the old steel liner? Many thanks.

    Thursday, September 29th

  • peterfall

    Sorry Frank I’m afraid I can’t comment on this without inspecting the house.
    Peter Fall

    Monday, October 3rd

  • Andrew

    Hi Peter

    I have a double flue chimney with one flue fed from the downstairs fireplace and the other from a fireplace in the bedroom and I am wanting to block the upstairs/bedroom fireplace up. I’ve read and been told that if you do this you have to fit a vent brick in the wall to allow the flue to breathe and prevent condensation build up in the flue which could lead to damp. I don’t really want to do this because the vents look ugly so was wondering if you could knock a hole between the 2 flues so the downstairs fire place would vent through both flues allowing the disused fireplace flue for the upstairs bedroom to breathe and prevent condensation which would allow me to fully brick up the fireplace opening without the need for a vent brick. Your feedback would be much appreciated.

    Thanks

    Friday, October 7th

  • peterfall

    Andrew
    In theory I suppose you could but the section of the upper flue that is below the cross over wouldn’t be vented and could be vulnerable. I would need to see the house and the layout of the flues to be able to advise you properly.
    Peter Fall

    Friday, October 7th

  • John

    Hello Peter
    I have a shared chimney stack with a neighbor which serves their bedroom and my sitting room . They have had the fireplace in their bedroom sealed with no air vent for many years. We have a disused but fully open fireplace below. The flaunching on top of the stack was deteriorated but seemed intact. Importantly the external stack was sealed up and so not vented. The chimney pointing was cracked and dislodged . Recently the neighbor had a roofer install a ventilated pot and an air brick in her bedroom. But the rest of the flaunching was renewed so as to completely seal my chimney opening. The external stack was also re pointed. Within 24 hours we had an awful smell of damp and musty air coming from our open fire place. It seems to be much worse first thing in the morning. What could have changed causing my fireplace and chimney to start emitting this awful smell?

    Thursday, October 13th

  • peterfall

    John
    Problems of smells are very difficult to diagnose without sampling the smell, seeing the situation and understanding the construction of the building/s. I can say that capping off the top of the flue will stop the natural flow of air up the chimney and therefore any smells that develop in the flue could drift down as the air temperature drops overnight but there are other reasons for damp smells to develop such as condensation, rising damp etc. Beyond that I’m afraid I can’t help. I can say that you need to rere-open the flue at the top to return the flue to its natural ventilation.
    Peter Fall

    Friday, October 14th

  • Alan

    Hi Peter
    I wondered if you could please give me some advice on the following, the house is 1980’s brick built and within the lounge we have a fire place with a gas fire fitted. The chimney appears to be an open stack, you can view all the way to the top, so not suitable for a coal fire (no vent controls). Generally we do not use the fire and rely on the central heating, the only issue is the fire place always is a cold spot. Can I just board the fire place up, thus removing this cold spot, or am I going to cause damp problems later? Maybe I could vent the chimney by fitting vent holes externally? Thanks.

    Sunday, November 13th

  • peterfall

    Alan
    I’m afraid I can’t say whether you will get damp problems later without seeing the house but I can say that if the flue hasn’t been used for a coal fire only a gas fire since it was built then the problem of dampness from salts lodged in the stack will not occur. These salts that cause the damp and necessitate the ventilation are from soot which you won’t get from a gas fire.
    A straight vertical flue could have rain and snow dropping down it so you might want to add a cowl on the top to deflect the rain and snow away.
    Peter Fall

    Monday, November 14th

  • jess

    Hi Peter,
    I have a renovated 1920’s semi that has 4 chimneys, 2 in each of the downstairs reception rooms and 2 in the bedrooms. These go up 2 separate chimney stacks on the external wall, which I cannot seem to get watertight. Each fireplace has been boarded over before I bought the house and have been capped off at the top. I have had roofer after roofer come to ‘fix’ the chimneys, one has repointed, one has redone the lead flashing and another has put small airbricks in the mortar of each stack (didn’t even know that was possible) but the problem seems to be worse than ever. In your opinion, should air bricks be at the bottom and the top or just one or the other?
    I clearly have water running down the chimney as the attic walls are soaked after last nights downpour but the flashing and pointing are all sound on the stacks. I fear I have two different types of problems as the water is running down the chimney in the attic, then there is a separate isolated damp patch on the downstairs chimney breast about 1m from the floor. It is safe to assume these were all working fireplaces once and after reading a lot of your comments about salts passing through the plaster, would the main remedy to fix this latter problem be to use the moisture resistant plasterboards?
    I understand it is hard to comment when you haven’t seen the property personally but any advice would be greatly received before I waste yet more money on remedial work that wont solve the problems.
    Many thanks,
    Jess

    Tuesday, November 22nd

  • peterfall

    Jess
    As you rightly say I can’t say what is the right solution for your house without first seeing it and the dampness. There is no doubt that if you removed all of the present plasterfinish and then applied a waterproof barrier such a polythene to the wall then dry lined the walls in plasterboard it will provide a short term solution. However the problem won’t have gone away so the damp could spread to the adjacent areas.
    The flues should have been ventilated when they stopped being used. If the cause of your damp staining is salts then I fear venting now won’t make it go away but it could slow down the spread to other areas.
    You may wish to get advice from a local Charrtered Building Surveyor. Have a look at the website http://www.rics.org and under the facility ‘Find a Firm’ look for a Chartered Building Surveying firm that specialises in the analysis of building defects (Building Pathology).
    Good luck
    Peter Fall

    Tuesday, November 22nd

  • Ian

    Hi Peter, fascinating read, thank you. We are in the process of removing an old back boiler and will block off the fireplace and place an electric fire on the finished wall. To my knowledge there has never benen a convential fire in this location. There is an air vent in the bedroom above the fireplace that I believe runs into the chimmney breast. In your experience (I accept that it may be difficult to comment unsighted) would this suffice in creating sufficient airflow to counter any potential damp or would we still need to install an (unsightly) airbrick into the wall?
    Many Thanks,
    Ian

    Friday, January 20th

  • peterfall

    Ian
    Yes, I can’t be specific for your house without seeing it first but I can say the need for ventilation is for those flues that have been used to burn coal or coke. The other fuels don’t seem to have the same problems from soot/salt deposits.
    I’m concerned that there is an old back boiler but not a coal or coke fire. Perhaps you had a combined gas fire and back boiler or maybe it was just never used.
    The air vent in the bedroom may be for another flue. Remember each fire has its own separate flue so don’t assume that it vents the lower flue.
    Sorry I can’t help more.
    Peter Fall

    Monday, January 23rd

  • Jon

    Hi Peter, Decorating in our bedroom over the weekend and have unearthed a rather damp wall and part of the ceiling adjacent to an unused internal chimney breast. Interestingly we also removed a layer of silvery paper and some black tar like paper on the surface of the plaster which was clearly used to stop the damp coming through.
    There has been a large amount of unsympathetic renovations in the 1920’s house, with the downstairs and upstairs chimney openings being boarded up with radiators in front, and central heating pipes routed into the chimney void. The chimney stack has also been removed to below the roof level (probably when it was last re-roofed) and just capped with concrete.
    I’m assuming the issue might be resolved through some ventilation, the question I have is, should I insert an air brick into the stack in the attic or in the wall in the bedroom? Obviously I’d prefer to have this in the attic where it is not visible, it would also remove the need to remove plaster in the bedroom to expose the brickwork.
    Many thanks,
    Jon

    Monday, January 23rd

  • peterfall

    Jon
    Without seeing the house I can’t say with any certainty but I suspect the salts came through some time ago hence the attempt at damp proofing the wall. If that is the case then ventilation on its own will not remove the problem. It will have to be replasetering I’m afraid with the special sulphate resisting plaster. Off course it may be another cause altogether and I can’t comment on that without seeing the house.
    Ventilation should be from the base of the flue to the top even if that is in the roof space.
    Peter Fall

    Monday, January 23rd

  • Marie

    Hi Peter

    I’ve recently moved into a 1930s semi detached house, which currently has an inset fireplace installed by previous owner, upon inspection by gas certified engineer I was advised that the flue was blocked and appeared to consist of approx 1 meter length of asbestos cement flue. I’m not sure what to do and if to have this section of flue removed and then have the blockage cleared and then proceed to blocking up the opening after removing the the current inset fire. Or should I leave this in place and block this up? I have had varying advise from builders with some saying to leave in place and seal up with plasterboard and venting the hole and other saying to have it removed, swept and new flue line inserted.Can you offer any advise? Also it appears there is a double chimney pot in the chimney stacks one with a cowl and one without, would you recommend having a cowl put on the other chimney pot to stop any rain etc from getting in? The chimney breast is on a party wall with my neighbours as its a semi detached. I’m not to fussed about having a gas fire but I want to be able to make it safe and damp free.

    Monday, January 23rd

  • peterfall

    Marie
    I’m sorry I’m afraid I cannot give specific advice for this without first seeing the house and the chimney itself.
    Peter Fall

    Wednesday, January 25th

  • Tony

    Hi Peter,

    We have recently bought a 1930’s 3 bed semi which originally had four fireplaces. The chimney stack is shared with our neighbours in the centre of the two houses.

    Three of these fireplaces are covered and have ventilation. The fourth has had the breast removed (downstairs) and is supported and sealed off at ceiling height.

    We have just had the stack re-pointed and I was advised that we should have it capped, in this case it is completely sealed off. They have laid slate tiles over it and covered the whole thing with cement. So we have one flue completely sealed and three with ventilation at the bottom only.

    From reading your site and others I’m thinking this is wrong and some ventilation should be provided at the stack. I don’t know if coal was used but given the age of the house it must have at some point. I did ask the roofers about ventilation and damp and they were clueless.

    Should I be worried about future damp issues?

    Many Thanks,
    Tony

    Thursday, January 26th

  • peterfall

    Tony
    I can’t be specific for your property but I would expect most 1930 houses to have burnt coal at some time. The exceptions being where there are bedroom fires and many homes never used these fireplaces.
    On the basis that it did burn coal in the past then I would recommend venting it top and bottom. If the top of the flue is capped off then air bricks should be fitted each side of the chimney stack above the roof into the flueway itself. This will allow air in and out but the capping will stop any rain or snow leaking in.
    Peter Fall

    Friday, January 27th

  • Claire

    I’ve just bought a 1930s semi detached property with two reception rooms. The back room had an old gas fire set into the original fireplace. On removing the old gas fire and mantelpiece/hearth it is clear that it was used as a coal fire originally. I intend to board up the fireplace and place a vent in the wall as you describe in earlier posts. I’m also going to get a chimney cowl fitted to protect the chimney from rainfall. However this wall is also the best wall to fit the radiator on when the new central heating is fitted, would it be okay for the vent to be behind the radiator or will this limit the air flow and prevent the chimney from being suitably ventilated? Many thanks, this whole thread has been so helpful!

    Wednesday, March 8th

  • peterfall

    Claire
    This should be ok. It’s the airflow across the top of the flue that draws the air out of the room. There needs to be a gap of an inch or so between the radiator and the vent to allow air to be drawn up the flue.
    Peter Fall

    Thursday, March 9th

  • Claire

    Many thanks Peter

    Sunday, March 12th

  • Chris M

    Hi Peter,
    I am renovating my 1935 cavity brick house, with two external chimney stacks with two flues in each. The flues were blocked up for sometime by electric fires and debris. I have now cleaned up and left the flues open to ventilate, including adding cowls.
    We have installed a multi-flue in the lounge flue.
    For our bedroom flue I have insulated at the fireplace opening to reduce heat loss, but installed a hit and miss vent to continue the ventilation into this flue.
    I’m wondering if I should install a breather membrane at the vent for two reasons;
    1. to prevent the internal warm moisture from entering the flue and condensing in the cold external flue (if this is and can happen?), and
    2. to reduce the draw across the bedroom to reduce the feel of a draught across the room? Would this continue to ventilate the flue enough?
    Many thanks for any advice.

    Thursday, March 23rd

  • peterfall

    Chris
    I’ve never considered what you are proposing before. My first reaction is no to the breather membrane as it will heavily restrict the flow of air up the flue. I then thought that maybe a moderate layer of mineral wool might do the job, say 75mm thick and laid loose so the air can pass through but at a rate that reduces the heat flow.
    I’m still not sure that would do the job but…..
    Peter Fall

    Wednesday, March 29th

  • Caroline

    Dear Peter, I have an 1860’s house. When I bought it three and a half years ago there was no damp. I enlisted a builder to knock out the two gas fires in the chimney breasts and create non functional fireplaces. The problem is that the replastering in the middle room inside the fireplace never dried. I left it some months originally as the work was completed in November and I thought the summer months would dry the plaster, however over the three years the problem has worsened and the entire inside and front wall of the fireplace is now damp up to about 50cm, with salt crystals. Another plasterer has told me today that I need a damp course, but could you advise why this problem has occurred? There was no issue with the wall before the work was done. Many thanks, Caroline.

    Thursday, March 30th

  • peterfall

    Caroline
    It is very difficult for me to diagnose a problem without first seeing the plaster and inspecting the house however it sounds like the plaster is contaminated by the soot deposits that are embedded in the wall. I suggest you try to replace this plaster with the sulphate resisting render and plaster as suggested in previous posts.
    Peter Fall

    Thursday, April 6th

  • John Ball

    Hi Peter,
    Congratulations on a great blog.
    I have an interesting situation where I have a central chimney in a 1950’s semi, which was built to initially accommodate a coal fire at ground floor, and 2 small gas fires in the bedrooms at first floor level.
    Some time in the past these gas fires were taken out and plastered over.
    What I would like to do is to install a new gas boiler at first floor level, and route the vent into the existing chimney.
    Would this be sensible? The difficulty would be knowing how the dual chimney is split.
    Kind Regards,
    John

    Tuesday, August 15th

  • peterfall

    You will need to talk to the heating engineer about which boiler can have a flue that goes up the existing chimney. The days when we could slip a flexible flue liner down the flue are gone I’m afraid. Most boilers these days work on a balanced flue which draws air down the outside of the pipe and pushes the fumes up the inside.
    As for the flues in the chimney breast and stack, they will all be separate. None of the flues should combine with another.
    Peter Fall

    Tuesday, September 12th

  • Jinni King

    Hi, Sorry if I’m repeating.

    I’m refurbishing a victorian(ish) semi with 2 breasts (4 pots). We’re insulating and going as airtight as possible with a heat recovery ventillatuon system. It therefore seems crazy for me to have air free flowing out of the chimneys. Is there any way you know if to successfully block a chimney so that it doesn’t need to be ventilated?

    Regards
    Jinni

    Monday, September 11th

  • peterfall

    The reason for the ventilation is to keep the inside of the chimney dry so if your ventilation system can also draw air through the flue before the vented air exits the house then that’s the solution.
    Another alternative is to remove the chimney breasts and the flues or you could just let the decay happen, strip off the affected plaster and replaster with a sulphate resisting render or dry line the wall with a clear gap to the salt affected wall.
    Peter Fall

    Tuesday, September 12th

  • Ed

    Hi Peter,

    I’m blocking up my fireplace with bricks, I have left a gap a little smaller than an air brick. Do you think this would be acceptable rather than using an actual airbrick ? I plan to purchase a vent for the hole once the plastering is complete.

    Saturday, September 16th

  • peterfall

    That is all that is needed.
    Peter Fall

    Monday, September 18th

  • Alex

    Hi Peter
    A couple of years ago we had a multi fuel stove installed in our detatched Victorian house (built around 1815) the stack looks in good condtion, had been rendered and has a cowel on top. There are no vents in the chimney breast upstairs, the room does get condensation but no more than any other. The problem seems to be in the bricks surrounding the stove. White Mould appears to be coming from ground level which we assumed was because the installer did not install a damp proof membrane. When contacted the company said ‘leave the stove door open to allow airflow and this should fix the problem’. Any advice before we get the other fireplace converted?
    Kind regards

    Alex

    Friday, September 22nd

  • peterfall

    I’m sorry Alex but this can only be dealt with by seeing the problem. If you are in the North East of England we could arrange an appointment but it would not be economic to travel further.
    Peter Fall

    Friday, September 22nd

  • Stacey

    Hi Peter.
    I purchased my first house around a year ago. The chimney breast downstairs had been taken out long ago, however there is still one upstairs and its capped at the top. There are no signs of any air vents anywhere in the house and although i havent spotted any dampness – my house does suffer massively with a condensation issue. There is also a odour, but it doesnt seem to me like a damp odour. There were visible signs of mould when i first bought the house, but none of it has since returned. There is also a huge amount of kingspan insulation on top of the rafters in the attic – i wasnt sure if this was normal process or could it be contributing tp the house not being able to ‘breathe’? Any advice would be much appreciated?

    Many thanks, Stacey.

    Monday, October 16th

  • peterfall

    Stacey
    If you put a vent in the chimney breast you will also need to remove the cap off the top of the stack.
    Condensation is a very complex problem that cannot be easily diagnosed without physically seeing the house. The main methods of reducing the risk of condensation are,
    Ventilate any moisture production at source – fans in kitchens and bathrooms and keep the doors closed when cooking or bathing.
    Ensure the walls, windows and roofs are well insulated
    Keep the heating levels up around the whole house.
    I susggest you have an independent inspection by a Chartered Building Surveyor to give you unbiased advice on the condensation risk.
    Peter Fall

    Tuesday, October 17th

  • Jane Tily RIBA

    If we are demolishing a 19C semi detached house and blocking up the chimney breast in the party wall (as it will become an external gable wall to the adjoining property), is there a need for an air vent in the new blockwork in front of the fireplace? Externally there is a rendered stone chimney stack with 2 clay pots. The fireplace appears to have been in use as there is a wood-burning stove in the recess. Should the chimney stack be capped, the fireplace blocked up with no additional ventilation? Also, further investigations may be required to confirm the condition of the flue in the adjoining property and whether this links to the flue which will be redundant. The adjoining property is 16C.

    Thursday, October 19th

  • peterfall

    Jane
    By leaving the breast in place, exposed to the weather you are running a major risk of moisture soaking the salts back into the party wall and no amount of ventilation will resist this. I can’t give you advice on how to do this as I haven’t seen the properties but I suggest you think carefully about leaving the breasts in place.
    Peter Fall

    Thursday, October 19th

  • Bronwyn

    Hi Peter

    I live in a 1900’s building, there are four flats, basement, ground, first and loft. The loft flat has issues with damp, a couple of years ago my neighbour put in an air vent in the wall of the chimney stack in his flat and a vented cowl on the chimney. He said the area above and below his vent has dried the wall out but there is still damp either side above the vent. He thinks this might be where the flues of the lower flats are. We had the brick work on the chimney sealed a few years ago and the lead around the chimney has been redone a few years ago and a waterproof resin painted around the top of it. He wants the rest of us to put vents in our chimney breasts. There is no damp in the rest of our flats, just the loft flat. Do you think if we put venting cowls in the other flues that it would dry out his damp wall or do you think we have to put the air vents in our chimney breasts to aid the air flow? We are a bit reluctant as they are ugly and we all have nice fireplaces!
    Thank you

    Friday, October 20th

  • peterfall

    Bronwyn
    If you have nice fireplaces put the vents in the bottom of the flue within the fire place. I can’t say this will cure the damp without seeing the house and the chimney breasts but at least it will ventilate the flue ways.
    Peter

    Wednesday, November 15th

  • Rhys

    Hi Peter,
    I have removed a log burner and want to keep the opening so I have the option of putting a new one in at a later date. What is the best way to block the hole? Can I plasterboard over the hole some sort of vent?
    Thanks

    Sunday, October 29th

  • peterfall

    Rhys
    You could block the hole with plasterboard but any soot falling down the flue will rest on the board and could attract damp causing the board to break down. I suggest you use a fire proof board that will resist the damp and remain rigid such as superlux.
    Peter Fall

    Wednesday, November 15th

  • Vicky

    Hi Peter
    We have a two stack chimney, we had the main from the living room lined and a multi fuel burner installed. We’ve just uncovered the old fireplace in the bedroom which had been breezeblocked and plastered over without an inside vent. We don’t suffer from any damp issues at present, the house is 1846.
    The fireplace would be too close to our furniture to use again but I’m hoping to re-instate it as a redundant feature. It has a standard pot and the lime mortar is in great condition. Yorkshire stone stack and hearthstone. It also lets a lot of light into a dark corner. I’m hoping to install a cast iron surround and narrow the opening by blocking off the sides but allow the back wall to be exposed. Would I be able to fit a transparent top to still allow the light in? The creative ideas are sometimes not practical so any help is greatly appreciated. Thanks for your time

    Friday, January 19th

  • peterfall

    Vicky
    I think you are saying the present flue from the bedroom fireplace is vertical, without any offsets or bends and you want to put some form of transparant cap on it. If the cap prevents air from passing up and out of the flue then this is a bad idea. On the otherhand if you fit air bricks below the cap into the side of the flue then you will maintain the air flow and this should keep the flueway dry.
    Peter Fall

    Tuesday, January 23rd

  • Tor

    Peter,

    Like many others I have read your articles and found them very helpful. We have just purchased a late Georgian terrace over 4 floors (in London). I wondered whether you had any advice regarding my questions/comments below:

    1) One side of the house has 3 fireplaces. We have lined the lower ground floor chimney and installed a wood burning stove. We have lined the ground floor chimney and installed an open fire. 1st and second floor fireplaces are in place and chimneys uncapped. Will the LG and ground chimneys still vent or does the lining prevent this?

    2) We have had a damp survey done by a DPC company. They have suggested injections, render and membrane across the entire LG floor. I am unsure as I can’t smell or see any damp. It smells a little musty but I suspect this is ventilation related as the kitchen has no extractor (we are putting one in)and the bathroom extractor appears to have been broken (unused).I can’t find a wet wall or any overt signs of damp (in fact it seems very dry). There is the odd bubbling of wall paper in one or two places (tiny bits) but nothing behind and I wonder if this is a condensation issue rather than a damp issue. I would hate to seal the house as I understand the ‘breathing’ principle (having read your articles). Any advice would be gratefully received.

    Kind regards,

    Tor

    Thursday, March 15th

  • peterfall

    Dear Tor
    As with all email queries I cannot give specific advice to your problems without inspecting the building first. London is a long way from Newcastle upon Tyne I’m afraid.
    1) All flues from fireplaces should be separate from each other. Lining the flue will ensure that flue is fully separated and the flue gasses safely discharge out of the top. Once you start using the fire those flues will be satisfactory as the heat from the flue gasses resists the problems of salts in the brickwork. The other two flues that are not being used will need to stay open so that air can rise up through and keep the brickwork dry.
    2) This is very much a problem I need to see and test to be able to give you advice. You could of course simply do nothing and see what happens. The way you use the house will be different to the previous owners and therefore any dampness from what ever source, could increase or decrease. The problem with waiting is if you then decide you must do something the mess can be quite nasty.
    Peter Fall

    Friday, March 16th

  • Torsten

    Peter, thank you for taking the time to respond. We have hacked off some more plaster/board today and it is bone dry so have decided to leave the DPC and see how we get along with heat and extraction! Have a great weekend. Tor

    Friday, March 16th

  • yvonne ferguson

    Hi Peter
    I happened upon advice given on your page about chimney closure. I am, TODAY!, having an old cupboard ripped out of corner of bathroom and a walk in shower installed. there is a chimney there and an opening stuffed with something like fibreglass and a board, freestanding over that. It didn’t occur to me until last night, after plumber said he would close up with plasterboard and skim, that that will mean it won’t be ventilated. This area is also going to be tiled. I don’t have a builder, just a plumber. As that area will be a shower I am not sure what to do about ventilation. I need to bring this up with the plumber obviously but I am doubtful he’ll know exactly what should be done. Should a vent go into chimney in loft (if that is possible, there’s not much loft above that room), should it go into the area where there’s a shower (which seems to me would cause more of a damp issue), on the side of the chimney (which is outwith the shower area). Do we have to cap chimney if there’s a vent? Would rather not, trying to find someone to do such things is always a problem

    Tuesday, March 20th

  • peterfall

    Yvonne
    It’s very difficult trying to imagine accurately what is being described but I presume the chimney breast is not being removed but the opening is being blocked up with plasterboard and skim and then tiled over to form the shower cubicle.
    If this room is on the top floor then I suggest you fit an air brick in the chimney stack in the loft as close as you can to the ceiling to ventilate this flue. Do not cap off the top of the flue.
    You say there isn’t much loft above this room so is the chimney an eaves stack or does it come through the ridge at the top? An eaves stack is very vulnerable to salts appearing in the room so even fitting the air brick may not work. The shower will generate a fair bit of humidity which will react with the salts and could give you damp staining problems despite the ventilation.
    Not a chimney problem but plasterboard doesn’t like getting wet so it is important that a membrane be applied between the tiling and the plasterboard and skim otherwise you will find the tiles start to peel off after a couple of years of use.
    I’m not sure your walk in shower in this position is a good idea.
    Peter Fall

    Tuesday, March 20th

  • Steve

    Peter, 1930’s mid terrace – bedroom fireplaces have clearly burned coal at some point. We want to keep fireplaces and have extended smart laminate flooring right to the back of where the grate would have sat. We now need to ensure that, grit and soot does not fall from the flue.
    What do you think of blocking the flue with a plug of ‘Fill and fix’ expanding foam with say, half a dozen lengths of 20mm plastic pipe set into it, just out of sight above the fireplace opening? Each piece of pipe would have a 90 degree elbow on top to save anything falling straight down.
    Or, alternatively a plug of rock wool insulation with the same array of plastic pipes providing the air flow path.
    The chimney pots are to be fitted with terracotta pepper pot caps. Thanks for your help, Steve

    Thursday, March 22nd

  • peterfall

    Steve
    Your idea of the 20mm diam pipes should work. A further thought is to have them discharge onto a tray hung beneath that will catch any debris and which can be periodically removed and cleaned.
    Peter Fall

    Thursday, March 22nd

  • Rich

    Hi, thanks for the article, exactly what I’m looking for. I live in a 1900 terraced cottage (ex-mining village) with a blocked chimney breast on a party wall. There is some damp around where the fireplace would have been, but no airbrick. (Have had a mixture of black mould, and white fuzz, likely efflorescence). I’d rather not have an air brick in the room (sucking up precious warm air, and looking ugly), so would it be possible to put one in from below floor level? It is a suspended wooden floor. I’m toying with the idea of breaking up into the base of the fireplace from below floor level. The source of the air ventilating the chimney will then be the same as the air that currently ventilates the floor voids. Any thoughts would be much appreciated! Many thanks.

    Monday, May 14th

  • peterfall

    Mr Rich or is it Andy?
    I’m sorry but without seeing tha damp I can’t say whether the air brick will help or not.
    Peter Fall

    Tuesday, May 15th

  • Jannice

    Hi Peter. I moved into a rented property. aged about 1960 I asked – and was given – landlords permission to decorate and do DIY. I took this to include remouve a hideous firepace and So I did and covered with plaster board.. Belatedy I see that this had had lots of ventilation up an old unused chimney formally used for coal (long time ago).
    The venting is into chimney below level roof level (built as such) but with an inbuilt built in ‘cowl at ridgeline.
    I have introduced some ventilation at low level.
    Do I need to worry? is dangerous??

    Sunday, July 1st

  • peterfall

    Jannice
    I’m sorry but without seeing the problem I cannot say.
    Peter Fall

    Monday, July 23rd

  • Jenny

    I don’t know if this thread is still running but here goes !
    I bought a 1950’s 1st floor converted house flat 6 months ago and have developed chest problems as well as numbness to my lips and swollen tongue every time I sit in the lounge. I can smell a strange toxic smell which is really strong to me but others cannot smell it. Could this be a result of a blocked up chimney that has not been vented at all. Have you ever heard of such a reaction? I have changed everything else in the room and I am not affected in any other even though there is a smaller chimney breast in the bedroom. Is there a test that can be done ?

    Monday, July 16th

  • peterfall

    Jenny
    I’m sorry but I haven’t heard of medical reactions from the effect of chimney breast salt staining.
    I have heard of medical problems from condensation mould. Lack of ventilation in the room/s can give rise to condensation mould and therefore I suggest you consider this area rather than the blocked off flues.
    There are public health companies that can test for the toxic mould from condensation.
    Peter Fall

    Monday, July 23rd

  • Kieren

    We’ve just bought a old ex local authority property, the 2 downstairs rooms have both got fireplaces one of the fire places has no air brick or vent, the other has a multi fuel burner with a flew system. In the loft the chimneys emerge together is the log burner enough to dry out the inside or does it still need a breath block? Any advice would be helpful.

    Wednesday, July 18th

  • peterfall

    Kieren
    The flues should not be connected. They may run along side each other but not connect. You need to consider each as a separate entity.
    Peter Fall

    Monday, July 23rd

  • Sean

    Hi Peter, not sure if this is still open for comments as your article was written years ago, but here goes.
    House = couple of hundred years old stone cottage renovated about a decade ago. All rooms are ground floor, with a master bedroom and bathroom having replaced a living room and kitchen either side of what was (anecdotally) a massive stone fireplace on one side (used for cooking) and a smaller fireplace on the other, both largely hidden away by now smooth vertical walls. Both rooms vent to the same chimney breast, and I’d suggest join as the chimney was swept days ago through the bedroom fireplace but soot came down into both rooms.
    There may well be a problem of soot salt penetration, from reading earlier questions and helpful solutions, but the main problem is that my bedroom just stinks of soot, even after having had the chimney swept. The chimney has been capped at the top by someone concreting a roof slate into place, so the only ventilation is from the open fireplace(s) at the bottom. This seems to have the effect of drawing sooty air down the chimney and into my bedroom, indeed it seems to have penetrated the carpet, which smells of it despite cleaning, so I don’t want to buy a new one until the problem is solved.
    Ideally I would like to block up the fireplace and NOT have any kind of ventilation into the bedroom, airbrick or otherwise, but earlier solutions seem to suggest that the chimney needs the ‘improvised’ cap replaced with a cowl that draws air up but is anti-downdraft, the fireplace blocked up using something called Superflux(?), and an airbrick needs to be inserted into the chimney breast in the bedroom. If that is the case (please confirm), the question remains at what sort of height? Some answers seem to suggest quite high, others low. The previous owner removed the ceilings so the room height now extends right to the roof.
    [As an aside, my surveyor said the underfloor needs venting with an airbrick(s) to the outside, so it would have been useful to combine the two jobs in one, venting the underfloor to the chimney breast instead, but I cannot see how this could be achieved as the bottom of the chimney is concrete, level with the floor; perhaps trying to kill two birds with one stone isn’t necessarily as clever as it might seem.]
    Thanks if you’re still taking questions and replying to them.
    Sean

    Thursday, July 19th

  • peterfall

    Sean
    I cannot give specific advice without seeing the property itself but having no top ventilation from a flue means the air will stagnate in the chimney. I normally recommend an air brick at the bottom in the blockeed up fireplace then a second through the top and your suggestion of a cowl is a good one.
    Peter Fall

    Monday, July 23rd

  • Steve H

    Looking to block up chimney, but would like to put a shelve into the recess where fire would go, and put my tv on the wall and have all the cables run down the inside of breast and into an MDF shelve built into the recess.

    Any suggestions/Tips/Advice ??

    Saturday, September 22nd

  • peterfall

    Steve
    I don’t know what you are wanting me to say.
    Sorry
    Peter Fall

    Wednesday, October 10th

  • Nel

    Hi, Please can you advise?

    Period 1903 semi-detached stonebuilt property.

    I have an external gable end wall that is stained. I think it is soot-stained as the black staining runs the full length from the Apex the chimney sits on the Apex, It splits into two where the chimney the runs bend. It starts to fade a bit about halfway down the wall towards ground level.

    20 years ago, tradesmen used a smoke bomb before fitting the flues for the two downstairs gas stoves. We also had the house sandblasted so the staining is more apparent.

    Two upstairs rooms have chimney breasts but no fires. I presume they have been blocked up and there are no vents in the bedrooms. Could this be causing the dark black run of staining on the gable end wall?

    Thank you for your valuable time.
    Nel.

    Monday, November 19th

  • peterfall

    Nel
    Not having seen the house or the stains it is difficult to be certain but I suspect the stain is soot deposits that have migrated through from the flue to the outside. If so the wall will be imprgnated from the flue to the surface so trying to remove the stains will be futile.
    Peter Fall

    Wednesday, November 21st

  • Barrie

    I need advice I had chimney taken down to floor level in loft.and had open coal fire removed. It is still vented in loft and in fireplace but I just can’t get home warm now if I block vent in loft and fireplace humidity go’s though the roof.and still can’t heat home up it feels like home is just drawing in the cold air.

    Tuesday, November 20th

  • peterfall

    Barrie
    If you have taken down the chimney fom above the roof to the loft floor level and vented the remainder then the only air passing through the flue is your internal warm air. Wher else could it be drawing air from?
    Peter Fall

    Wednesday, November 21st

  • Graham

    Good morning Peter
    We live in a cottage built in 1760 which was renovated in the 1970’s. During this work, a cement liner containing white asbestos (as confirmed by lab tests) was installed into the chimney stack on the gable end of the property.
    When the chimney was swept recently, the sweep discovered a broken piece of liner. We have been advised by an ARCA registered asbestos removal company, to seal the chimney off, as removal of the liner could be very problematic, causing damage to the whole chimney stack. We intend to install at least one, possibly two, external air vents on the bottom of the chimney stack, (internal vents not being viable due to the failing of the liner).
    This liner, as far as we know, runs from the fireplace right up to the chimney pot, which is fitted with a cowl.
    1. Do you recommend capping the liner?
    2. How many vents would you recommend?
    We’re concerned that the presence of the liner will prevent air flow, from the external vents out through to the chimney pot.
    3. Will it be a problem that the circulating air will be from the outside, as we understand that ideally, it should be a warm air flow through the vented chimney?
    Any advice you can give us will be much appreciated.
    Graham

    Saturday, November 24th

  • barrie

    in need of advice chimney stack is in center of home internal wall between front and back room. After a hetas installer did a bad job i had to have stack taken down to floor level in loft. instead of having an inset fire opening in back room i now have a large square opening where log burner has been removed. this has a 8″ opening straight flue to the top(floor level loft).if i leave this open top and bottom humidity in home go’s up to the high 70%. with cold air coming down from loft. the front room still is inset with vent and does not have a draft. Air gos up rather than down into room. If i put insulation boarding over in loft and flue opening down and leave a small 1″by3″ opening to both it does not help still have cold air coming into room from loft.and cant heat home. if i block both no help stops cold air but home still feels cold and cant heat proper. at mo got bottom 8″ opening blocked. humidity under control but still takes an age for home to heat. as of the cold damp air in stack. could i as stack nolonger exhasts home fill this with vermicerlight to fill voild and seal top and bottom ???? or would it be better to seal in loft and leave open downstairs and add vent ceiling level in bedrooms so the air can cerulate home and heat stay within home?.

    Saturday, January 5th

  • peterfall

    Barrie
    The need for ventialtion is to keep the flueway dry. If the flue doesn’t now go outside then dampness shouldn’t penetrate the stack so the ventilation shouldn’t be required. On that basis you could just cap off the base of the flue.
    Peter Fall

    Wednesday, January 23rd

  • Rich

    Hi, I employed a roofer to cap my chimney (old mid terrace property). He used some sort of slab and cemented over the opening to seal it. I have been told this is illegal, unsafe and will cause damp from poor ventilation. Where can I find the specific regulations relating to these issues? He tells me I don’t know what I’m talking about, but a quick search on the net assures me I’m correct but I need to be accurate in my response to him. Do you know what regulations I can specifically quote to him?
    Many thanks
    Helen

    Wednesday, January 16th

  • peterfall

    Helen
    I’m afraid I don’t know of a written regulation on this only that stopping air from flowing through the flue can result in the soot salts migrating to the internal face of the chimney breasts resulting in damp staining on the plasterwork.
    Peter Fall

    Wednesday, January 23rd

  • Matt

    Hi, my fireplace has been blocked up and I plan to open it up to have as a focal point in the room. I am not putting a fire in place. Would it be okay to open it up block off the flue from inside with plasterboard and add a vent?

    Wednesday, January 30th

  • peterfall

    Yes, that should be ok. If you are putting a vent in the bottom of the flue you will need to incorporate a removable tray underneath to catch the soot and debris that falls down over time.
    Peter Fall

    Thursday, January 31st

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