Rising damp is the action of water moving vertically through porous building material, which is in contact with the ground. This is brought about by the drying action of air on the upper surfaces which causes the wall to act like a wick, drawing water upwards from the ground by capillary action, which then evaporates from the surface into the atmosphere. The moisture will continue to rise until it reaches a height where, unless evaporation is possible, gravity pulls it down again.
Water coming from the soil will have various dissolved Nitrates, Chlorides and other salts (hygroscopic ground salts) which will be carried upwards into the brickwork and plaster. As the water evaporates, an increasing amount of these salts will be deposited in the wall. As ground salts are easily dissolved they also readily attract moisture from the atmosphere.
As a result of this the plaster will always be damp or contaminated, even after the rising damp is cured. For this reason the plaster is normally removed when treating rising damp. Wood rot in adjacent timbers may often be as a result of rising damp in a wall.
moisture to enter the structure in a horizontal direction. Gravity may cause the downward movement of the resulting dampness.
Causes of penetrating damp may be from sources difficult to control such as defective brickwork, cracked render, faulty pointing, poor flashings or rainwater goods. The cause can also emanate from a defect within an adjacent property outside the owners control.
Penetrating damp has been proven to be responsible for a high percentage of dry rot attacks found in
Penetrating damp can create isolated patches of dampness that increase in size after periods of heavy rain and tend to disappear in long dry spells of weather.