DAMPNESS in a cupboard

[Rigger]

I have a flat with a small cupboard which has 2 wall which form part of the outside wall that is to say they are in the corner of the building. The one wall has dampness below a window which seems to be getting worse. I accept and understand that in all dampness cases the source needs to be found 1st and treated, but the outside wall looks fine and as the dampness is not major i would welcome a cost effective and easy way to prevent/slow down the effects. I heard about a paint which if applied inside will help, also is there something i could paint outside to protect the brickwork against dampness. I WELCOME ANY COMMENTS AND THANK YOU IN ADVANCE FOR YOUR ADVICE.

[Stuart Noble]

Any oil based paint on the inside might help a little (no point in buying anything special) but it sounds like you may have a problem with the window sill. Either it's porous or the joint between sill and wall needs sealing

[Owain]

Are you sure it's not condensation? In which case, ventilating the cupboard, and perhaps using expanded polystyrene lining paper on the walls, might help.

Dampness below a window might indicate the drip groove in the underside of the sill has been bridged.

Owain

[mail]

Dear Rigger As i understand it you have two sources of dampness One under a sill. All the subsequent posts are right. I would also add that by now the plaster may well be hygroscopic and thus you may need to replace it in a suitable material such as a sand:cement render. To test for hygrocopicity you can get simple chemical tests for salts or you can measure the dampness and compare it to the relative humidity in non-rainy weather and see if there is a correlation. It would be quicker just to replaster! I personally would fix the cause and wait and see if it went and only after fixing the cause (drip groove, negative slope on sub sill, joint opening up etc etc) and it still being wet would I conclude that it was hygroscopic and replaster. The cupboard sounds like a classic case of condensation but with the absence of data I cannot advise. There are only four categories of dampness in buildings. Rising - lateral penetration - pipe leaks - and condenstion

Chris