Rising damp and penetrating damp - causes
What causes rising damp?
Moisture that is drawn up from the ground to an approximate height of 1.2m (depending). Causes, are from a failed DPC (Damp Proof Course), or a lack of DPC (Damp Proof Course), or in houses with cavity walls - bridging from the outer-wall to inner-wall , often by something trapped in the cavity. Moisture is drawn upwards through the mortar (and eventually brickwork) in a capillary action from the foundations. Hygroscopic salts and minerals form deposits tend to form on the surface of the walls following the chemical reaction caused by high levels of moisture. Plastered walls are highly susceptible to moisture and tend to crack and blow.
What causes penetrating damp?
Damp that occurs in walls through the walls (rather than rising-up from the ground. This occurs from cracks in the render/brickwork, and decayed thin walls.
Penetrating damp is more likely to occur in single-skimmed walls as a cavity helps prevent the moisture bridging to the inner wall.
