A damp-proof course is a physical or chemical barrier built into a wall, just above ground level, to stop groundwater wicking upward into the brickwork. Older properties (particularly pre-1875 or so) sometimes have no DPC at all; in others, the original DPC has failed, been bridged by a raised flower bed or path built up against the wall, or damaged during renovation work.<\/p>\n
Chemical DPC injection involves drilling a series of holes along a mortar course near the base of the affected wall and injecting a water-repellent chemical (usually a silicone- or siloxane-based cream or fluid) that spreads through the masonry and creates a barrier to rising moisture. It’s typically followed by re-plastering the lower section of the wall with a specialist salt-resistant render, since the original plaster will usually be contaminated with salts drawn up by the damp and won’t simply dry out and become sound again.<\/p>\n