Mould

Mould is made up of tiny fungi that grow wherever a surface stays damp for long enough. Indoors it shows as black, grey or greenish spots, usually in corners, on ceilings, behind furniture, around windows and in bathrooms. Outside, together with moss, it turns north-facing walls green.

Behind mould there is always water: condensationCondensationMoisture in the air turning to water on cold surfaces such as windows, outside corners and ceilings. It is the most common cause of mould indoors. from poor ventilation and cold walls, a leak from the roof or a pipe, or rising dampRising dampMoisture from the ground that climbs up inside walls through the pores of the materials. It shows as stains, blown render and salts at the foot of walls.. If the cause isn't found and fixed, the mould comes back, even through fresh paint.

Before painting, the mould is cleaned off, the surface treated with a suitable fungicide and left to dry thoroughly. An anti-mould paint can then be used. Because the spores irritate the lungs, it is wise to wear gloves and a mask while cleaning and to keep the room aired.