Rising damp, a worldwide phenomenon, is a major cause of decay to masonry materials such as stone, brick and mortar. Even when mild it can cause unsightly crumbling of exterior masonry and staining of internal finishes. It may also cause musty smells in poorly ventilated rooms.

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What is rising damp?

Rising damp occurs as a result of capillary suction of moisture from the ground into porous masonry building materials such as stone, brick, earth and mortar. The moisture evaporates from either face of the wall (inside or outside), allowing more to be drawn from below. The height to which the moisture will rise is determined by the evaporation rate and the nature of the wall. The normal limit for rising damp ranges from 0.5 to 1.5 metres above ground level. Rising damp may show as a high-tide-like stain on wallpaper and other interior finishes, and, when more severe, as blistering of paint and loss of plaster. Damp walls encourage the growth of moulds, which, with the high humidity, can lead to health problems for occupants. Externally, a damp zone may be evident at the base of walls, with associated fretting and crumbling of the masonry.