Waterproofing and damp proofing quotes

Diagnosis comes first

"Damp" is a symptom, and the cure depends entirely on where the water is coming from. The same stain on a wall can be caused by rising damp, rain driving through the wall, a leaking pipe or condensation. Treating the wrong one wastes the money and leaves the problem.

Rising damp and the damp-proof course

Walls are built with a damp-proof course (DPC), a waterproof layer near the base, to stop ground moisture rising. Rising damp happens when there isn't one, it has failed, or it's bridged: soil, paving, plaster or a flower bed built up above the DPC gives water a way round it.

Removing the bridge, by lowering paving or soil, or cutting plaster back above the DPC, sometimes fixes the problem on its own. Otherwise, a new chemical DPC can be injected into the wall, and the salt-contaminated plaster is replaced with a suitable render. Plastering over rising damp without treating it just moves the tide mark higher.

Flat roofs, parapets and balconies

Flat concrete roofs, balconies and the tops of parapet walls are where most waterproofing work is done. Common systems include torch-on bitumen membranes, laid in sheets and sealed with heat, and liquid-applied membranes, painted on in layers with a reinforcing fabric. The system has to suit the surface, the slope and whether people will walk on it.

On a flat roof, ponding water is the enemy. A good contractor checks the falls and the outlets before covering everything in a new membrane.

Showers and wet areas

Leaking showers usually leak through failed grout and silicone, or around the drain, because the shower was never properly waterproofed under the tiles. A lasting fix often means lifting the tiles, installing a waterproofing membrane, and retiling. Sealing the surface helps temporarily, but water already under the tiles has to go somewhere.