Healthy Homes

What is Condensation, Damp and Mould?

Mould is a form of fungus that is usually produced in damp and humid conditions. It can grow in any home and typically can be found on items such as wallpaper, wood, and carpet. Mould will continue to develop until it's cleaned and removed. As it has potential to harm our health, early action is needed. 

The principal causes of mould are humidity, condensation, penetrating or rising damp and ineffective ventilation. It is important to understand each of these and take preventative actions.


Condensation is the most common kind of damp. It is caused by moist air condensing on walls, particularly in rooms with a lot of air moisture. Condensation can be worsened by poor ventilation and heating that comes on and off, as this allows warm, damp air to condense.

You may notice water droplets on windows or walls, see dark mould appearing, particularly on glass or around windows, and / or notice an unpleasant smell. This can provide ideal conditions for mould especially mildew which causes black patches on walls and fabric. If left untreated, condensation can damage paint and plaster and cause window frames to decay, so when you see it form you should wipe it away with a cloth.

Penetrating dampness:

A leak in the roof or gutter, rainwater pipes, mains water supply or other pipes in the building as well as defects in the pointing of brickwork can cause penetrating damp issues. Defects of this sort can be relatively straight forward to repair once they have been tracked down, although the dampness may then take some time to dry out.

Rising dampness:

Rising dampness can affect ground floor rooms and is caused by water from the ground getting into the walls and floors, often because a damp-proof course (DPC) or damp-proof membrane (DPM) has failed or (in the case of many older buildings) because the property was built without such damp proofing. Residents are advised against piling rubbish or soil up against the outside of the house above the level of the DPC.

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