Persistent Rising Damp takes on chlorides, nitrate and other salts from the soil, which are deposited into the plaster as the water evaporates from the surface. Such salts are Hygroscopic, with the effect that the plaster has a tendency to be persistently damp, particular during periods of high Humidity in the atmosphere, even after Rising Damp has been stopped.

Many older properties can be affected by Rising Damp due to the lack of and effective Damp Proof Course (DPC). Existing Damp Proof Courses can be bridged i.e. high external ground level or when the walls have been plastered the plaster runs to ground or the DPC is an old DPC and has broken down over time.