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. It potentially occurs where there is no damp proof course (DPC) or where the DPC has been damaged or bridged. 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 generally ranges from 0.5 to 1.5 meters above ground level. Rising damp may show as a stain on wallpaper and other interior finishes, blistering of paint and loss of plaster. Damp walls encourage the growth of mould, which with high humidity can lead to health problems for occupants. Externally, a damp zone may be evident at the base of walls and in extreme situations, with associated fretting and crumbling of the substrate.