Why Important
Concealment of damp areas is not recommended, but may occasionally be acceptable if the enclosed space is ventilated. In particular, untreated damp areas lead to fungal growth and unhealthy living conditions. Hiding the problem can lead to legal problems with regard to Duty of Care and ill health of the buildings occupants.
What to look for
Raised surface in large ‘bubbles’ on the wall. Hollow sounding plaster when tapped. Discolouration of the plaster work or wallpaper surface. Mould growth on the wall surface.
How to fix
A plasterboard lining on battens is the simplest method of concealment, but all battens must be pressure impregnated with a non-staining, inodorous preservative and both the wall surface and the back of the lining should be treated with fungicide.
Alternatively, a barrier, such as corrugated pitch or bitumen lathing, can be fixed to the stonework and plastered over; in this case, the undercoat should be 1:1% browning plaster to clean sand, which will not shrink on drying.
Re-plastering with a suitable plaster (as all specialist companies do) also hides the signs of damp (and failed damp-proofing systems!).
Avoiding creating problems
Do NOT ignore.