Waterproofing is necessary when Penetrating Damp (as opposed to Rising Damp) travels across or down masonry.
Where high ground or below ground areas (i.e. your basement / cellar) are affected your surveyor will inform you that these areas require a tanking system.
There are many methods of tanking and all are designed to deal with lateral penetration of moisture from high and below ground levels. They can be grouped into three categories:
Cement-based Water Proof Render (Tanking)
Water proof renders are one of the oldest methods of water proofing and have been used by the remedial industry for many years.
The application of multiple coats of a water proof render (using sand and cement incorporating a quality waterproofer) to a previously prepared surface is designed to stop water entering the tanked area. However there are many disadvantages:
The Cavity Drained Membrane System is, as the name suggests, a polyethylene studded sheet which is fixed to the walls, floor or ceiling with specially designed plugs with fitted seals.
It creates a cavity between damp masonry and a new wall surface. The base of the wall carries a drain channel which normally runs to a sump pump or manhole, thus relieving water pressure.
The system can be either dry lined or plastered directly on to to achieve a smooth plastered finish. This method of tanking:
These are often cement based, two part flexible coatings which come pre-packed in powder form. The surface must be prepared and a salt inhibitor applied. The slurry can then be mixed and applied by brush.
The system has the same disadvantages as the Water Proof Render system with the added problems of eroded or perished brick requiring special attention, and the high cost of the materials.