Rising Damp Most commonly used building materials such as concrete, brick and natural stone are porous as are the mortar and bedding materials in which they are laid. Surrounding foundation clays and soils provide a source of moisture, which is absorbed into the masonry components of the structure by capillary action. The upward movement of this moisture causes rising damp. The level to which the damp will rise is determined by the efficiency or otherwise of any original damp proof course, the volume of the water supply, evaporative conditions over the wall surface and humidity.   The Effect The term rising damp is generally used when dampness appears above the floor or skirting board level of the property causing damage to brickwork, mortar joints, plaster, paintwork or wall coverings. This can in most cases be attributed to the lack of, or failure of, the building's damp proof course. Contributing Factors: No damp proof course provided at construction stage Progressive deterioration of the original damp proof course Replacement of timber floors with concrete Building extensions using concrete floors abutting existing walls New Spilt level extension below original dampcourse Bridging of the damp proof course from building rubble in cavity walls Wall surface treatments that form a bridge over the damp proof course Ineffective, or lack of, sub floor ventilation Concrete paths or verandahs finished above and bridging the damp proof course Incorrect concentration of a mixture in original damp proofing mortar Garden beds built up above and bridging the damp proof course Associated Problems: Many methods have been tried to hide or disguise rising damp. These usually involve the placement of waterproofing materials or sealing compounds over the damp surface. This sometimes hides the damp temporarily, but in most cases causes a chimney effect that forces the moisture further up the wall. This does not solve the problem and creates greater expense in the permanent corrective treatment. Where rising damp is present, the moisture level is sufficient to propagate timber destroying fungi, which can attack skirting boards, architraves and window frames. Brickwork, stonework and mortar joints can be seriously affected by natural ground salts, which may cause eventual structural problems.   Lateral Damp Lateral damp as distinct from rising damp is caused by moisture migration through porous walls due to a variety of factors. These can be rainfall on absorbent bricks and wall facings, faulty downpipes, roof plumbing or even soil built up too high against external walls. Lateral dampness can give the same appearance as rising damp but requires different corrective treatment. Specialised equipment and materials are used by F.G. James to determine and remedy lateral damp.   Hygroscopic Salts Natural soluble mineral salts are commonly found in soil. When rising damp occurs, nitrates, chlorides and efflorescent salts migrate through the masonry in solution and accumulate on the wall surface as a white powder. These salts are hygroscopic and attract moisture from the atmosphere, particularly during periods of high humidity, and give the effect of persistent dampness and associated damp smells. Salt contaminated solid plaster will continue to attract atmospheric moisture even after the rising damp has been stopped. To prevent this secondary damp problem the affected area of solid plaster must be removed. The removal and replacement of plaster forms part of the FG James system.   For further information on Rising Damp please call (03) 9885 9444 or send an email to enquiries@fgjames.com.au