Does our plaster need replacing after leak?

[Garth]

hiya, we moved into our house 3 years ago. within the first few months we realised we needed the felt on our roof replaced after signs of leaking on the ceiling and chimney breast downstairs. We had the felt replaced 2.5 years ago. The damp patches dried out a bit - they were 35% on the damp meter we used and reduced by 10-15%. these patches are still at about 24% even after 2.5 years. The immediate surrounding area have much lower readings. We have no mould or salts and the room doesn't smell damp. We are pretty sure the leaking has been fixed but it seems those original damp patches are either still damp or attracting any damp in the atmosphere. We keep the room well heated and ventilated. We don't know if we need to continue to be patient and let it dry or replaced small sections of ceiling and plaster on chimney breast if these areas are permanently damaged and attract damp. we don't know what sort of plaster has been used or if there's plasterboard. The plaster finish is rough on the walls and the ceiling is papered. Sorry to ramble on...hope someone has some advise. Thanks, Andrea

 

[erikwoolf]

I had a similar issue with a historic leak along the chimney breast that left a damp patch that persisted long after it as all repaired and dried out. I ended up removing the affected plaster area and replastering. Two years in and there is no sign of any damp in the area.

 

[Garth]

when you said there was a damp patch did it continue to remain damp and that's why you replaced the plaster?

 

[malcolm]

Damp meters are designed for use on wood where they work because the wood has fairly good electrical insulation and any water conducts a bit.

On plaster they are inaccurate. Plaster is more conductive than wood in the first place, and if any water has got in from brickwork at some point it will have carried some salt with it so the plaster will conduct electricity even better even after drying out.

The only reason to replace plaster is if you have an actual damp problem causing the wall to get wet in which case something more breathable would probably help. Damp meters are useless on plaster so don't rely on one of those to tell you if you have damp.