Damp proofing is a protective process to ensure moisture cannot pass through the walls of a building to the interior.
Rising damp is not the most common form of dampness encountered in buildings; this is left to condensation . However a high proportion of older buildings are affected by rising damp to some degree or another. In general, walls prior to the 1871 did not have damp courses and properties upto 1970’s had inferior ones, which allowed the damp to rise in capillary action. In many cases of rising damp in more modern walls the causes are often traced back to bridging/ breaching of the D.P.C. (Damp Proof Course).
Rising damp in buildings may be defined as the vertical flow of water up through a permeable wall structure, the water being derived from ground water. The water rises through the pores (capillaries) in the masonry. In other words the masonry acts like a wick.
By natural evaporation from the surface of walls, rising damp seldom occurs above a height of 1.2 metres unless forced higher by being sandwiched between two impervious layers of render, gloss paint or wall paper. Temporary measures, like cleaning the surface, replastering or just repainting can actually make the situation even worse.
The rising damp also carries with it hydroscopic salts (nitrates and chlorides) and as dampness evaporates from the wall surface the salts are deposited in the plasterwork, which build up into a concentration, that can absorb moisture from the air making the situation critical.
Rising damp can be more serious than just causing aesthetic damage, structural damage to the base of the wall can also occur which if left unchecked could lead to dire consequences.
There are two methods of tackling salt damp or rising damp. The other alternative is to place a chemical damp course at the lowest point of the wall, to create a barrier preventing any more rising saline water entering the wall above this point., This method gives a 20 year guarantee. The other method is a physical damp course and is completed by removing a course of bricks in stages we will then put a new Polyethylene DPC this conforms to BS6515 all damaged bricks will be matched and replaced, called 'Undersetting'. This method if done correctly will solve the problem, but is usually more costly, messy, time consuming and can compromise the structural integrity and the originality of the building. The other thing to consider this method does not remove any salts that is already in the plasterwork unless the plaster is removed as well. The other alternative is to place a chemical damp course at the lowest point of the wall, to create a barrier preventing any more rising saline water entering the wall above this point. We are one of the few companies in the south of england who offer both physical and the chemical pressure injected damp proofing methods. We believe the chemical pressure injection method, which has been perfected over many years, is far superior to any other type of damp proofing solution but are happy to discuss both solutions with the customer
website by karmaan