Benham Preservation have been fixing problems associated with dampness for over 40 years, but this page is purely for your information.

So how does damp and moisture start and more importantly what sort of damage can it do? Most building materials are porous to some extent and thus have the capacity to absorb moisture. When a wall is built in contact with the ground, the soil, which normally has a high moisture content, will cause it to become wet. The drying action of the air on the upper parts of the wall will cause the wall to act as a wick. Water will move up the wall, mainly in the mortar by capillarity, and evaporate from the surface. The presence of nitrate and chloride salts in walls where rising dampness occurs helps to confirm diagnosis.

In well established rising damp situations, a large proportion of the dampness in the wall may be there as a result of these salts. This is described as the hygroscopic moisture content, as opposed to the capillary moisture which is directly attributable to the rising damp from the ground. In addition to increasing the wall moisture, these salts cause discolouration of decorations and wallpaper and crumbling and disintegration of plaster. On brickwork they may accumulate on surfaces, causing the familiar salt efflorescence associated with rising damp.

Special laboratory procedures have been developed to ascertain the hygroscopic and capillary moisture contents of masonry, and these can prove useful in special circumstances.