Basements waterproofing

When assessing a symptom of a perceived damp problem in a Georgian basement, one point is fairly certain: Georgian basements were damp. The general absence of dpcs and dpms, and sometimes inadequate ventilation, make an ideal breeding ground for wood-boring weevil, furniture beetle and both wet rot and dry rot.

In respect to refurbishments for accommodation, once a basement is tanked, lined, decorated and adequately ventilated it should be habitable. Because of the generally high market value of Georgian properties, owners need to rely on good refurbishment design and workmanship to retain value. It is often the case that defects arise from negligent work or poor design principles rather than faulty systems. However, living in basements also requires good housekeeping skills to keep moisture under control. If ventilation systems are overridden or poorly maintained, condensation can give rise to damp-staining and mould growth.

Earlier retrospective waterproofing techniques tended to rely on asphalt tanking to line the walls or bitumen membranes behind brick linings, and these can fail if water pressures increase or joints fail. Basement waterproofing leaks normally are only discovered once the structure has been occupied, and while patch repairs are possible, they tend to be unreliable. Any remedial work or investigation is going to be very disruptive. The cause of damp needs to be diagnosed carefully, as it is important to isolate the effects of condensation. A normal moisture content of 40–60% is acceptable, and long-term monitoring can establish moisture patterns.

Basement waterproofing should always be considered as a 3-dimensional problem, and it is important to establish whether the system will be required to provide or has failed to provide resistance to water pressure and whether additional controls on water vapour are also required.