Damp proofing describes the control methods used to prevent excessive dampness in buildings. Given a basic understanding of the causes and cures, rising damp can be prevented by the simple injection of a remedial damp proof course using a damp proofing cream designed for the professional builder and those competent in DIY.

Rising damp is a form of dampness caused by the upward movement of ground water through a permeable masonry wall having no effective damp proof course. The water rises through the pores in the masonry via a process called capillarity.

Capillarity is an electrochemical action which attracts water molecules to mineral surfaces, enabling water to move vertically through pores of a certain size despite the counteractive force of gravity. The same process is responsible for the movement of moisture from tree roots to tree tops via intricately stacked hollow cells. Fortunately the pores in masonry are not as fine as those in trees and rising damp in walls rarely ascends more than about one metre in height.

Rising damp only becomes a problem if it affects vulnerable materials or finishes that are in contact with the wall. For example if it affects timbers such as joists, skirting boards or the bottom of door frames such as to provide wood rotting potential or if it causes wall plaster or wall coverings to deteriorate or become stained.

Effective remedial damp proofing requires a chemical damp proof course injection in accordance with BS6576:2005. The remedial DPC should be sited along the base of a wall at a level that is at least 150mm above external ground level and internally beneath ground floor joists, or close to the floor if solid.

In the UK you should use a BBA approved chemical damp proofing treatment that is specifically designed to be introduced into the mortar joints. The mortar presents the only continuous passage ascending up a wall through which water is able to rise. Therefore a mortar bed joint is the only layer that can function as a damp proofing layer. Introducing a DPC into just each brick or block unit along a stretch of wall will not stop the water rising through the joints between.

Contrary to common belief a silicone DPC does not form an impervious physical barrier. Chemical damp proofing is an effective method of lining the pores along a stretch of masonry wall with a silicone resin water repellent. For the purists, silicone rising damp treatments work by neutralising the charge attraction of the masonry pores to water molecules.

An essential requirement of BS6576: 1985 Code of practice for installation of chemical damp proof courses is to replace wall plaster that has been contaminated by the ground salts deposited by the rising dampness. Best practice, though not always the most convenient, is to leave the plaster above the new damp proof course on the wall for several months following the DPC injection. This allows the salts to surface during the drying out process and the extent of plaster replacement to be properly ascertained.

The 21st century has brought us modern Ultracure damp proof cream technology that has been independently assessed and accredited by the British Board of Agrement (BBA Certificate 02/3961). Holes are drilled into the mortar at 100-120mm intervals and DPC cream is dispensed to fill each hole. The damp proofing cream comprises a blend of silicone and a silicone carrier.

The effectiveness of the rising damp treatment relies upon formulating the correct balance of ingredients to ensure that the silicone migrates fully along the mortar bed, thereby maximising the effectiveness of the damp course treatment.

Whilst you would be wise to call in a competent tradesman to do any future plastering work, you can buy professional DPC cream online in a specialilist DPC kit or in damp proof course builder packs or in easy to use DIY damp proofing kits, saving hundreds of pounds in the process