Condensation, Painting and Decorating walls & ceilings
Damp on the inside of an exterior wall is sometimes blamed on water penetrating from outside or rising from
the ground when the real cause is condensation. Cooking, washing, etc – it all produces water vapour which condenses on cold walls.
Totally blocking up fireplaces and draught sealing windows and doors, makes it worse, because with no draughts there’s nowhere for the water vapour to go. In London, fireplaces are not so much in use lately. Anything which keeps surfaces in the room warm will help. Double-glazing prevents condensation inside windows and lining cold walls with a dry wall ( stud wall ) and insulation stops the damp from settling there. It also helps with soundproofing the walls.
Damp patches: some alternative barriers
Where the amount of damp coming into a room is slight, it can be kept from spoiling the decorations by applying any waterproof barrier between the plaster and the paper. Ask your builder’s merchant what he has in stock and what he would recommend; the materials range from paint-on waterproofing liquids, through pitch-coated lining papers to metal foils and foil-surfaced plasterboards. Pitch-coated papers are applied with a special waterproof adhesive; so are metal foils – the adhesive used with these dries quickly and you’ll need to smooth the foil out at once, working gently with a soft cloth to get rid of any air bubbles, before it has dried. Overlap joins by about an inch. If you tear the foil, stick a strip of foil at least an inch wide over the tear. The foil surface can then lined and painted, or wallpapered. Nail or stick foil backed plasterboard in place, foil side towards the wall. This will act as a barrier against the damp soaking through and help protect inside surfaces against the formation of condensations.
Stain blockers can be used before painting, however, sometimes the damp stain will show through the final painting coats in time, if the damp problem has not been solved before painting and decorating. You might need professional Painters & Decorators for the job.