Internal damp on chimney stack

[Brooktop]

I have damp coming in on the bedroom wall, where the chimney stack is located. It seems to be coming in through the mortar because it is patterned.

A damp specialist said that it was probably caused by condensation build up because the fire in the lounge wasn't being used and that it would dry out when I started to use the fire again. I've since had the old inefficient gas fire taken out and have been having a real fire (the chimney was swept before using it).

Far from the problem getting better, it has probably got worse. Apparently the guttering, flashing and flaunching are ok. A builder had a look; the first obvious sign of a possible problem was a couple of cracked slates. He replaced these (cost £105)....but that didn't solve the problem. He came back and has re-pointed the back of the chimney stack (costing £120, but it was in a poor state and needed doing)...but that still doesn't seem to have sorted the problem. I don't think the guy is trying to rip me off...as he didn't think the pointing would sort it.

Does anyone have any other suggestions? The roof is too high for me to get up to, so I have to take his word for it that the other usual suspects (flashing, guttering and flaunching) are ok. Could it be that the chimney simply needs lining? btw - my house was built in 1946 and does not have cavities.

 

[JohnD]

Do you use the fire regularly, so that the brickwork tends to be warmed through?

If you can get into the loft, you can have a look for any evidence of gaps or rain penetration.

 

[Brooktop]

Hi - the fire is used at least 3 times a week for a minimum of 2 hours at a time.

There is no evidence of ingress of water or damp in the attic.

 

[noseall]

the staining your talking about may not necessarily be damp. it could be that the bricks have reached their saturation point of combustible deposits and its just eeking through.

 

[Brooktop]

so how would I sort that? I have a de-humidifier on the go during the day...which does dry it out....and then after it rains, I'm back to square 1.

 

[noseall]

when a customer of mine encountered this problem, it was suggested by a surveyor that s.b.r. be used as a barrier. that is, hack off the plaster where necessary, back to the brickwork and wire brush. mix neat cement with s.b.r. solution and apply to the brick work, mix a rendering gauge with s.b.r as an admixture and apply to the "tacky" s.b.r./cement as a scratch coat, apply a second coat as normal, then skim.

 

[viewer]

Noseall sounds spot on. You say it comes back with rain - have a look when the rain comes. Often if the problem is due to salts from the old coal fire then the damp will show as a patch before there could have been time for the rain to penetrate. Sometimes it will appear as the humidity increases before the rain arrives. Salt inhibitor before replastering usually works, but many people choose a big mirror.

 

[Brooktop]

Is that before the sticky waterproofing layer that noseall recommends or afterwards?

Damp patches can appear before rain...which I'd put down to the cold. The previous fire was a living flame fire, but obviously still gave off carbon deposits....but the chimney was swept before I installed the real fire...and there wasn't much soot; I think the previous owner kept the c/h on 24/7.

 

[Brooktop]

After doing a bit of research on the net, it would seem that it may well be damp coming through the chimney breast. Condensation and the acids from the fire attack the mortar, which then seeps through in patches. So stripping off plaster, and rendering etc would just be a temporary solution and would not get to the root of the problem.

Looks like it's a flue re-line (circa £1.5k). I may also have to strip the damp plaster AS WELL. Great...just what we need to hear seeing as we have a baby due in the next month! Ho hum!

 

[tawelfryn]

If your definately sure its not a leak from your roof and it is as noseall suggests (which makes sense to me as I have seen it before) Instead of 1.5k for a flue, try £150. Strip wallpaper (if there is) Seal with a sealing solution (it helps) dry line, with batten or dot and dab new plasterboard on the affected wall. re-plaster or scrim the joints and sand in, re-paint

 

[Brooktop]

Thanks guys - I've got a chimney flue co. going round to have a look. They think it may just be that because there is one flue within the stack (one from the bedroom, that must have been bricked up years ago) that is not used, it's not getting ventilation.

My only concern is that the damp patches appear across the full width of the stack.

I'll let you know what they say.

 

[Adzy]

Hi guys
I would say be careful on who and how much you spend on this area.
It could be a number of things and whilst a lot of people make positive and fair guesses tread carefully,one thing is for sure we have had a lot of rain and houses flats bungalows are simply just not completely waterproof.
Another thing that's for sure don't do anything till it's dried out your wasting time and money
The chimney stack out of the roof is a solid thing and when it exits the roof should be sat on a full lead tray across the whole chimney then dressed down,if you don't have the tray and if you do with the amount of rain we have had most bricks are porous ie take water on board so once the brick is saturated it will travel in out anywhere it can go I believe from a practical view that this is what has and is going on with most of the houses with this problem
I also understand we are building house in the wrong way today in not letting them breathe we are sealing everything up and this also adds to the problem when water decides to make its way in