Dampness on internal walls may be caused by:
- Condensation (kitchen, laundry, bathroom — improve ventilation by opening external doors or windows);
- Water penetration from above;
- Penetration across the wall cavity (accidental bridging of the cavity by mortar droppings or by an incorrectly installed wall tie or inadequate flashing around a window or door — difficult to rectify without skilled assistance, so consult a builder);
- Rising damp (absence of a dampcourse in masonry houses or bridging of a dampcourse by a water absorbent material, build up of a path or garden adjacent to the wall — visually check at least once a year, preferably when the moisture is visible on the internal wall).
In bathrooms where plaster linings have been used as fixing surfaces for tiles, check to ensure that a breakdown in the sheet is not occurring due to moisture penetration adjacent to the bath or shower recess.
Where a shower screen is adjacent to a door frame check that the joint between the screen and the wall adjacent to the architrave is remaining waterproof, as the moisture can cause dry rot in the timber, even under paintwork.