Recurring damp in attic bedroom where chimney breast has been removed (now supported by steal beam)
Anonymous user 03/03/2024 - 3.27 PM
Hi, any help greatly appreciated.
We’ve had a chimney breast removed in our top floor attic bedroom. The neighbours wouldn’t agree to remove the stack even though neither of us use it and it’s capped, so the stack is supported by a steal beam. The beam was plastered in (double boarded) but ever since we get huge damp patches every time there is heavy rain. We’ve had the chimney recapped, there are ventilation bricks, we’ve had the lead lifted, a better runaway created in the valley and then the lead relayed and sealed into the chimney, and had the chimney repointed. And we still have damp patches where the breast used to be on the plaster around the steel beam. We’re at a loss. Removing the chimney isn’t an option. Do we need to do something internally? Damp proofing?
Any ideas?
Thanks
Are you a tradesperson and able to answer this question?
Sounds like you have done everything correctly, in checking that the ingress is stopped and the area well maintained. When steel is cold it creates a surface ideal for condensation - could this moisture be warm air in the loft turning to condensation on hitting the cold steel surface ? (this is Annabelle not a surveyor - but this may be the answer ?)
Answered13 January 2020
4
Anonymous user
I probably would of left it open and used as a vent if your neighbour will not allow it removed, would guess your only option is to somehow vent it and get air flowing through as its probably a condensation trap now its closed and doing nothing, very difficult question to answer mate other way is maybe insulate the area that's cold and damp from the warmth
Answered13 January 2020
0
Anonymous user
You’ve done everything right but by the sounds of it your getting damp where you’ve fixed your boards to the brickwork via dot and dab. For easiest method especially with it being in the loft would be to install a cavity drain membrane. This provides a barrier from the brickwork for your plasterboard to fix to
If the chimney was ever used , it will have deposits of ammonium sulphate in the brick work, removing the actual chimney only removes three sides and in your case also leaves the top.
Ammonium sulphate is hygroscopic and will become wet when the humidity is high and particularly when it’s been raining but the rain or rain water is not the issue, it’s humidity .
This salt cannot be removed though rendering over it with a waterproof render will help keep it back from exposure to humidity; that is the only ‘cure’ !
Those other contractors should be ashamed of them selves and I suggest they research this subject prior to carrying out further work !
Answered14 January 2020
0
Anonymous user
It could be either one of the above . It needs to exposed to cure the problem but the best thing to do would be to drop the stack once you have exposed the bad area then get the job done properly, using the correct boards and to make sure it’s well insulated
I think the first answer is correct. The support for the stack is steel and is now effectively embedded in plaster. This is ideal hunting ground for condensation. Just like the cold mirror gets fogged in the bathroom during a shower, the same is happening in the loft when humidity is high such as when it rains. ~Consider the installation of a PIV unit to combat the condensation.
