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Damp Proofing

Damp patch remaining on chimney breast

Anonymous user 25 October 2022 - 4.07 PM

In our bungalow we had the chimney taken out because there was a damp patch at the top of the wall. We suspected rain was penetrating through the chimney (there was no protection on top of it) and then through the brick and plaster. However, about a year on from removing the chimney the patch is still there and clearly saturated. It hasn’t spread though so we are unsure as to whether it is moisture that has been retained within the brick and needs the plaster removing, then a dehumidifier before replastering? Up in the loft there is no sign of moisture coming through the roof etc either. Are there any other potential causes/solutions?

4 answers from MyBuilder tradespeople

Best answer
Eco Greener Home LTD

No reviews yet

Swindon

Sometime what appears to be an isolated damp patch on a chimney breast or on a wall where one has been removed are actually not caused by external penetrating water but by hydroscopic salt. When fossil fuels are burnt such as coal or gas, because they are formed underground, they absorb minerals and when they are burnt produce a by-product of salts which remain within the walls. Hydroscopic salts unfortunately attract moisture from the environment that is naturally within your home which can lead to damp forming in an isolated area and not spreading. Contacting a damp specialist with PCA qualifications should be able to point you in the right direction how to confirm and remedy this

Answered

25 October 2022

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7
Shaws Building Services

No reviews yet

Cheadle

All that the previous contractor has commented is absolutely correct. However, you don't need to spend thousands with a PCA registered company. You need to hack off the salt affected plasterwork ensuring that all traces of gypsum are removed. Iyou paint the walls wink tanking compound (and not leave gaps) then replaster the walls with something like Limelite (Travis Perkins sell it) and skim the following day. That should do the trick!

Answered

10 November 2022

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1
Lee Hunter

No reviews yet

Sheerness

100% agree with eco greener home Ltd answer. I am a PCA qualified surveyor and this answer is correct.

Answered

11 November 2022

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1
GN Building Services (Stafford) Ltd
Rating: 4.8 out of 54.8525 reviews
Stafford

Well, you are right, an uncapped chimney can certainly cause damp. But so can various salts that tend to get deposited in or on bricks. These always attract moisture. The chimney has been removed, so that is not the cause. Salts might well be the explanation, so might be leaking guttering, cracked render, no internal ventilation etc. Assuming salts, the simplest, cheapest cure is simply to use foil lined plasterboard all around the area. Re-plastering will never work. Foil lined plasterboard is impervious to moisture and is cheap to do. If this does not work, you will know that the cause is a lack of internal ventilation. Depending on the property, you must have trickle vents above windows, maybe air bricks. Extractors in bathroom and kitchen. Tumble drier venting to outside. All properties will get damp patches if inadequate ventilation. Hope this helps.

Answered

18 November 2022

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0