Rising damp is a common phenomenon in older buildings, particularly those constructed without a damp-proof course. In simple terms, it is caused by ground-water rising upwards through a wall, much in the same way as oil would rise through the wick of a lamp. The visible characteristics of rising damp are dampness on the lower part of a wall, sometimes up to 1.5metres high, and often with a horizontal water mark towards the top of the rising damp front. In severe cases ground salts will be visible, particularly at the apex of the rise. These deposits of salts are hygroscopic and can absorb water directly from the air.
In many European countries the existence of rising damp has been acknowledged in building codes since the 19th century.
The presence of rising damp in walls is undesirable for a number of reasons, including decorative spoiling, loss of thermal efficiency, and the potential to cause decay in embedded timbers.
Below-ground Masonry, Crawlspaces and Basements, Damp proof courses and Waterproof Tanking, Ground floors, Moisture in Materials, Penetrating and Rising Damp, Product information, Rot, Mould and Bugs, Technical Reference
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