damp on my chimney breast

[nelly1859]

hi everyone,

got a problem at home and wondered if anyone may be able to help.

I live in a flat converted from a house and it is terraced. I am on a steep hill and the houses are staggered in level. My chimney breast has a damp patch on it which is at the height of my neighbours floor. Here is the work I have done so far.

Capped of all the chimneys including the neighbours.
Bitchumin painted the exterior of the chimney stack and the top round the chimneys.

There is no sign of damp in my roof and no damp anywhere else in the flat.
This is why I assumed it would be coming from the chimneys or the stack itself.

Help what do I do next as I have no idea what it could be now.

Thanks.

Nelly

 

[xerxes]

You have my sympathy: these problems can be difficult to solve.

Capping the chimneys (hope you've allowed for ventilation) will only help if the rainwater falling down the chimney is finding its way through the masonry to the outside of the chimney breast. If that's what been happening, you will have to wait for water already in the masonry to dry out, which won't happen quickly. A pencil line round the edge of the present damp patch will show you whether the patch is getting bigger or smaller.

If the damp is getting worse, you'll need to look for a solution elsewhere. You don't mention the flashing between the chimney stack and the roof. This may be where the problem lies; or you may have a puncture in the roofing felt. Or there could be several separate problems which are all contributing to the damp problem.

You may be best finding a skilled and friendly roofer who is willing to come back if you're still getting problems after he's done the first repair.

(An afterthought: consider the possibilty of a plumbing leak in that area.)

 

[nelly1859]

Thanx will give the flashing a go

nelly

You have my sympathy: these problems can be difficult to solve.

Capping the chimneys (hope you've allowed for ventilation) will only help if the rainwater falling down the chimney is finding its way through the masonry to the outside of the chimney breast. If that's what been happening, you will have to wait for water already in the masonry to dry out, which won't happen quickly. A pencil line round the edge of the present damp patch will show you whether the patch is getting bigger or smaller.

If the damp is getting worse, you'll need to look for a solution elsewhere. You don't mention the flashing between the chimney stack and the roof. This may be where the problem lies; or you may have a puncture in the roofing felt. Or there could be several separate problems which are all contributing to the damp problem.

You may be best finding a skilled and friendly roofer who is willing to come back if you're still getting problems after he's done the first repair.

(An afterthought: consider the possibilty of a plumbing leak in that area.)

 

[noseall]

it is likely to be hygroscopic salts, and nothing to do with external damp penetration.

 

[nelly1859]

how do i deal with the hygroscopic salts does this mean the chimney needs to be swept ??

Thankyou for a response and i look forward to hearing from you

nelly

it is likely to be hygroscopic salts, and nothing to do with external damp penetration.

 

[noseall]

you can't remove the salts from the brick but you can help prevent them from migrating through the plaster.

the existing plaster needs removing local to the problem area and allow a decent margin around the effected area too.

an s.b.r. cement slurry should then be applied to the masonry with a render coat being applied to the still-wet slurry.

skim as normal with an appropriate finish.