Basements waterproofing

Tanking

Tanking is used where basements have been formed, but can be applied as an additional coat to existing walls if the background is stable. This technology was not available to most Georgian properties. Systems can be applied internally or externally using painted, trowelled or sheet membranes, but it is difficult to apply tanking retrospectively on external surfaces. If applied internally, water pressures can cause the layer to blow.

Tanking systems are not recommended unless drainage is provided above the wall/floor membrane lap position and the site is relatively free-draining.

Integral

Mainly used in the construction of new basements, these systems use concrete retaining walls that resist the ingress of water in differing amounts, depending on thickness, the amount of reinforcement and the density of the concrete. Compaction of the concrete and the installation of water stops at the construction joints are critical. Additional tanking may also be required.

Drained

Drained cavity and floor systems enable moisture to penetrate the retaining wall. Profiled polythene membranes are applied to the vertical surfaces to form a drained and vented cavity layer. For example, Delta Membrane Systems produce damp proof systems for retrofitting basements.

The moisture is collected in the sump and pumped away. These systems are thought to be much more reliable than other waterproofing systems for retro-fitting. Access hatches for the inspection and maintenance of internal gullies should be provided where possible. Sumps may need back-up pumps. Fixing the membranes to the walls must be carried out with great care.