Tanking & waterproofing of basements and cellars

Tanking & waterproofing of basements and cellars

Structures that are either partly earth-retaining or completely below ground level can often be prone to hydrostatic pressure of moisture (lateral penetration). If the basement or cellar is not a habitable area, this does not really pose a problem. However, if more living space is needed, various options can be considered in order to transform the basement or cellar into habitable accommodation. Our surveyor will be pleased to carry out an inspection and provide a detailed report and estimate on the most suitable method.

BS8102:2009 is the British Standard for waterproofing below-ground structures. Working to this standard ensures consistently high quality and also reduces the possibility of waterproofing systems failing. There are three types of protection available.

Cementitious Tanking
The traditional method of tanking is a cementitious multi render coat applied directly to the wall, incorporating a waterproofing agent. However, this relies on the substrate being in a sound condition. The slightest movement or a hairline crack in the substrate could be enough to cause failure.

Cavity Drainage Membrane
The modern tanking alternative is to use a plastic dimpled membrane, usually incorporating drainage channels and a sump chamber and pump. It is not intended to withstand water pressure, but to produce a dry usable space by diverting water away from it. Walls can then be finished with insulated plasterboard dry lining and skimmed with plaster. Alternatively, render can be applied directly to a meshed membrane.

Dry Lining System (without drainage)
A ventilated dry lining system can be used without full drainage provision in order to give protection from damp or salt contamination. Plastic membrane can also be used for this purpose. However, this method will be not be recommended where standing water exists, as it will not resist water pressure and so cannot be guaranteed waterproof.

Whichever method is used, two important factors should be considered when making a cellar habitable. Mechanical ventilation (if no windows exist) and adequate heating.

Waterproofing to Floors
In some situations, our experienced surveyor will recommend Epoxy resin as a suitable medium for tanking solid damp floors, which are otherwise in a sound structural condition. Usually, two coats will provide a durable waterproof membrane, which will tolerate normal mechanical wear.