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Damp Proofing Question
Damp problem under bay window
A company cleared a damp problem in 1998 under a bay window. They did not replaster inside. I now have damp patches on the same wall could this be damp in the plaster still or the original problem?
It really depends how the damp was addressed in the first place. It's common to see damp under bay windows but sometimes it is caused by rising damp, sometimes it is condensation and sometimes it is penetrating damp which can be due to poor rainwater drainage, badly sealed windows, damaged sills etc... If the cause of the problem hasn't been addressed then it will return.
Firstly, did you get a guarantee for the work? It is normally 25/30 years for the areas that have been treated. If the company has gone into liquidation then sadly your guarantees die with the company. Back then, some companies would have drilled and injected chemicals into a course of brickwork, some would have painted on cementitious tanking (looks like cement) and others may have used a membrane. In 99% of cases we use the plastic tanking system as it introduces a waterproof barrier and creates great airflow for moisture evaporation. If you can, try to get the same company to treat the damp and plaster, we do this because if there are ever any problems in the future, the book stops with us and you can't have one company/trade blaming the other.
Hope this helps you.
Answered 24th Sep 2013
We'd need more info to be more precise but here's a quick bit of guidance.
The fact the wall was not replastered could be critical. If the original cause was penetrating damp (water coming through the brickwork) then the expectation is it will have brought salts through with it. These then dry out in the plaster but are hygroscopic - in other words they soak up moisture - this time from your room - to cause wet patches that are worst in winter. If the area develops mould across the middle of it the original builder may have been right not to replaster. Instead, it sounds far more like condensation which is caused by an imbalance in the heating, insulation/exposure (bays are really bad for this) and ventilation. Ventilation is our expertise. If it is ventilation then the most obvious tell-tale sign is if you are also getting condensation on the windows as it gets colder.
Answered 22nd Oct 2013