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Damp Proofing

Damp Patches in upstairs bedroom caused by condensation?

Anonymous user 23/02/2024 - 2.30 PM

I am having issues with my kids bedroom. We live in a rather old property and when we bought it, it had been sat empty for about 5 years and had a leaky roof so the place was pretty wet! We dried it all out with dehumidifiers and had the damp course done, roof re done etc. All was fine until I noticed 2 damp patches one bedroom. These patches are either side of the window (on an external wall) which has a bank and rather a lot of trees opposite. 1 patch is various distinct damp patches covered with the small black mold spoors and the other is above the skirting board and again has mold. Both patches never spread and when I clean the mold off the damp that is left is always in a very distinct pattern. I open windows at opposite ends of the house to ensure ventilation. No where else in the house has any issues and I cannot understand if its condensation why its forming there as there is nothing to cause it. The bathroom has an extractor fan and the door is always shut and this is the only thing upstairs that I can think could cause the problem. One person told us it was condensation and the another didn't seem to think it was! Can anybody shed any light?

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1 Answer

Anonymous user

Hi, The black spot mould is condensation. This can be caused by cold bridging or dampness within the walls. Basically the affected areas are colder than the rest of the wall creating a dewpoint on the walls where the moisture from the ambient air within your property condenses more readily than the higher temerature surroundings. Things to look for- Gaps where moisture or cold air can enter the fabric of the building Dot'n'dab plasterwork where the adhesive dabs form a cold bridge from an outside wall Leaks from roofs Leaks from gaps to lintels or cills. The leaks can be through quite small cracks gaps or openings and can be some distance from the internal signs as water/moisture can run from point of entry and settle in a different place. Also possible that interstitial condensation is forming within a cavity and causing damp patches or mortar is lying on wall ties forming a cold bridge. Or If wall ties have corroded this can cause a gap in the mortar and allow moisture/cold air to cross the cavity. This can often be seen by horizontal splitting in mortar courses/gaps in external pointing. These issues can be detected quite easily by a trained professional and inspections are often free. If in the North East area drop us a line through My Builder and I will inspect the problems for you. Mike Davison cssw Dryspace Maintain Ltd.

Answered12 September 2011