Identifying the Causes of Dampness

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Penetrating Dampness above ground

Identifying penetrating dampness is mostly about looking at the areas of dampness and then looking for defects that are allowing water to penetrate. In general penetrating dampness occurs in solid walls. Water will hit the wall and be absorbed finally appearing internally. Whilst the source of the water is rain, poor rainwater goods, such as gutters and downspouts, may affect the volume. Usually external observations will show algae growth in areas where leaks are occurring. Internally the patches will come and go dependent on rainfall.

Penetrating dampness below ground

This occurs in cellars and is a result of ground water penetrating the wall. It is found on external walls mainly but will also be absorbed into adjoining walls. In wet weather the moisture levels will increase and in severe cases liquid water may flow through the walls directly.

Rising Dampness

This is caused by water from the ground rising into the walls above ground by capillary action. It does not normally rise above 5 feet high (less in stone walls over 12” thick) and is usually seen as a tidemark on all walls in contact with the ground. In warmer dry weather the tidemark may drop leaving staining and sometimes decorations can delaminate and have a crunchy feel when pressed. Ground salts crystallising behind the decorations cause this. Externally look for the existence of a damp proof course and make sure that soil or paths are not bridging it.


This is caused when warm wet air meets a cold surface. Any water is then released and condenses on the surface. It is normally found in rooms that are poorly ventilated, cold and in areas where water is produced. Intermittent heating and cooling can also contribute. Very often mould growth is seen in the corners of rooms and behind large items of furniture.

Having identified the cause of the dampness thought must then be given on ways methods of treatment.

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