Damp around chimney breast

Tolley · Post by **Tolley** » Tue Apr 24, 2007 12:43 pm

An excellent site. I have tried searching it for similar topics; my apologies if I’m going over old ground or have posted to the wrong forum.

We have a problem with damp around the top of a chimney breast in an attic bedroom. We hadn’t noticed a problem until we came to re-decorate. Repairs to the roof and external chimney stack were professionally made a few months ago so I don’t think water is getting in from outside. There are gas fires either side of the stack in rooms downstairs – one is in use, the other isn’t. However, the dampness is fairly even all the way round, so its not clear if it’s some form of condensation coming from inside the chimney. We have tried picking the brains of builders who were undertaking other work at the time, but they didn’t have any suggestions. I’m at a loss what to do next.

A friend suggested painting PVA over the affected area to create a barrier. Is this a sensible idea? If so, can I use a universal PVA or does it need to be a special type? Should it be used neat or diluted?

A previous owner had used some sort of plastic film-coated liner under the wallpaper. As we hadn’t noticed damp staining of the wallpaper previously, I presume it must have worked. Is this a good way of dealing with the problem? Can anyone advise me what it’s called and if there are any tips on its use?

There again, am I totally barking up the wrong tree? All advise would be gratefully received.

dewaltdisney · Post by **dewaltdisney** » Tue Apr 24, 2007 1:21 pm

Hi Tolley,

You must start with basics. This is in an attic space so we must assume that this is not rising damp. The next cause would certainly be from water creeping in through the stack or roof joint. You say that the stack has been repaired and I take this to mean that lead flashing, pointing and flaunching, the cement seal on top of the stack surrounding the pots is sound. Has the stack been saturated though as this can take a long time to dry out? Next ensure that there is not a water pipe that is leaking into the wall a little further down (unlikely)

Gas fires produce a damp exhaust gas and if the chimney is not clearing well then I suppose it is possible for dampness to permeate the top of the stack. Again this is unusual.

PVA is water soluble and would be useless for sealing. You would need something like Aquaseal but you really need to identify the cause first.

The dry spell we have had should be seeing an improvement. My money is on a continuing problem with the stack.

Hope this is useful,

DWD

Fats · Post by **Fats** » Tue Apr 24, 2007 1:26 pm

Hi Tolley and welcome.

First of all just because you had professionals doing the roof doesnt mean they dont cock up. What was wrong with the stack originally? They might have sorted the problem out then..or has it appered after the work?

And whatever you do dont PVA over it.

Post by **ultimatehandyman** » Tue Apr 24, 2007 1:30 pm

I agree with DWD,

The other chimney that is not in use- has it been capped off or has it been sealed in the room? If so this could be the cause!

Identifying a problem like this is never easy without seeing it.

The PVA is a bad idea. Once the problem is fixed you can repair the plaster if needed and then paint over the area with stain stop, but the cause of the problem needs finding first.

It does sound like there could be water getting in somewhere, did you notice any improvement after you had the remedial work done?

Tolley · Post by **Tolley** » Tue Apr 24, 2007 2:46 pm

Thank you very much for the prompt responses and warning me off the PVA option.

We had originally got the roofer in because of the damp. He said that there hadn’t been anything major and had done some re-pointing and repaired some cracks in the cement work around the chimney stack. I can access a portion of the chimney via a small roof space above the bedroom; it does feel dry to the touch compared to the area around the top of the chimney breast and immediate area of the ceiling below.

We had assumed that the roof work had sorted the problem out, and left the area to dry for a few weeks before papering over. The damp started to show through a few weeks later.

At maximum, the damp stain spreads about 12 inches down the chimney breast and across the ceiling in the bedroom. It doesn’t seem to be weather related. As the pipeworks to the water tanks etc in the roof space are a fair way from the chimney, it doesn’t appear to be a leaky pipe. It doesn’t seem be greatly different compared to before we had the roof work done, though it’s hard to tell.

The house is unusual in being tall and thin, and was originally two terraces knocked together. I think there may originally have been three flues in both houses, so the chimney stack probably contains a total of six (and from memory there are 6 chimney pots). Two are connected to the gas fires and there is an open fireplace in another room. The equivalent in another room is definitely boarded over with no obvious ventilation grill. I vaguely recall a builder mentioning that these type of houses had hot water boilers in the kitchen, so I guess that would account for the other flues, but I don’t know where they would have been originally sited. Again – no obvious ventilation points. How would I tell if a chimney has been capped off and what is the significance of this?

If the source of the problem is due to condensation in the flues, would it be reasonable to simply Aquaseal over the affected area or would I be storing up problems for later. How would you suggest I proceed, especially with regard the two “mystery” water boiler flues if they are part of the problem?

Your advice is much appreciated.

Post by **ultimatehandyman** » Tue Apr 24, 2007 2:52 pm

sealing over the patches is not really curing your problem, it is merely masking it!

I think you need to take a look at the chimney pots and make sure thay have not been capped off, if they have it would be a good idea to get them uncapped and then fit ventillation grilles in any of the internal chimneys, which are not in use. This will allow good ventillation and should hopefully stop any damp thst has been caused due to lack of ventillation or trapped damp air.

petengade · Post by **petengade** » Tue Apr 24, 2007 8:45 pm

We had a damp chimney breast, it had a coal fire in the grate before and seemed to attract the damp on a wet day and stain would appear.

Cured it by sticking bacofoil on the breast with pva

then gave another coat of pva

then papered on top of that.

Still ok to this day, broke every rule in the book but it cured it. have done three others the same way with no come backs.

bye the way all chimneys were open fire places , maybe soot left after being swept attracted the moisture.

jason123 · Post by **jason123** » Tue Apr 24, 2007 9:47 pm

Alot of chimney carry flue liners these days, rain could be entering between the vertical flue and mortar.

carhartt kid · Post by **carhartt kid** » Wed Apr 25, 2007 2:10 am

Start from the outside and work in mate. Check the flashing, pointing and capping etc. I mean really check it!!! Hairline cracks etc! Make sure you've the right cowell and vent caps, and that no tiles are out of place. If you've a chimney liner check its not damaged or blocked!

Also check the type of pattern of the damp. Is it a water mark, mould, or rot. Every type of mark has a name??? If you can take a photo post one on here!

I personally would hedge a bet that it being an attic room, may be purely down to humidity and moisture build up in the cavity between the roof skin and the room below???? Cold surfaces draw moisture out of warm air and then pourous surfaces just wick it away leaving a mark!

Yet again photos photos photos!!!! If you can get some posted it may save you a load of wasted time and money!

Tolley · Post by **Tolley** » Wed Apr 25, 2007 2:00 pm

Thank you again for all your responses.

The damp that showed through the wallpaper ran down each side of the chimney to form roughly a triangular shape and similarly across the adjacent area of ceiling, to a maximum point of about 12 inches from the chimney. Now that the wallpaper has been stripped off, there isn’t anything to actually see, so nothing off note worth photographing. There are no obvious signs of mould or rot which I presume means that it is likely to have been simply due to water.

I have had previous dealings with the roofer and am inclined to trust him. He said he had given the chimney a thorough examination and had repaired some hairline cracks.

Regarding checking whether the chimneys are capped or not, what should I be looking for? If each is covered with a vented top, is this sufficient? Is it absolutely necessary to have vent lower down to create a draught?

Things did seem to improve last summer, which may suggest that humidity is the problem, as suggested by carhartt kid. So what are my options? I’m quite tempted by the simplicity of the bacofoil option suggested by petengade. Are there any other proprietary products that I’d be better of using?

I very much appreciate that so many people have taken the trouble to offer advice.

dewaltdisney · Post by **dewaltdisney** » Thu Apr 26, 2007 8:41 am

With respect to Cahartt moisture rising through the house in the form of condensation would settle on the surface of the cold spot where it would condense back to water. This damp appears to be in the brickwork coming out as the cover over decoration kept it contained in the past.

I still feel that water is getting in and not able to dry out so the brickwork is getting saturated. The flaunching around the pots needs to be checked as this is a classic place to gatheror pool water if there is no run off. Step flashing around the stack should also be checked as should the stack pointing.

You really need an independant to check this out.

DWD

Third Eye · Post by **Third Eye** » Fri Apr 27, 2007 6:07 pm

How did you decorate over the damp area's ?

Did you use any sealers prior to decorating ?

Did you use emulsion or wallpaper over the damp patches ?

Tolley · Post by **Tolley** » Mon Apr 30, 2007 8:38 am

We had thought the problem had been sorted out by the roofer as the area had dried out. We simply wall papered over and covered it in emulsion paint.

Would using bacofoil as a liner or a proprietary water sealant be better? Any recommendations of a type?

Post by **ultimatehandyman** » Mon Apr 30, 2007 5:07 pm

You can get special paint now, but you are masking the problem rather than fixing the cause :!:

http://www.screwfix.com/app/sfd/cat/pro ... 2&id=79059

Third Eye · Post by **Third Eye** » Mon Apr 30, 2007 5:53 pm

Oky.

If the area dried out AFTER the roofer done his/her work, then this suggests that any small leaks have been correctly fixed.

Going by what you have wrote so far Tolley it SEEMS to me that you have just assumed that by the roofer fixing the roof, that this fixes the Water Marks.

This is NOT the case. When constant water has made on-going contact to Interior Plaster or Gyproc then this causes the Interior Plaster or Gyproc to turn a yellowish colour where the water has made constant contact. This yellowish colour stays there even after an water leak or damp has been fixed. Even when dried out.

Sometimes the yellowish stain is hard to see if the surfaces are already an yellowish colour.

Best thing to do is coat the yellowish stained areas with Dulux Trade Stain Block Plus. I recomend this product as it is water-based, therefore totally breathable.

Follow this advice if the surfaces are DRY.

Are they CURRENTLY dry ?