As a basic principle, tanking involves applying a water-proof substrate to the basement walls. This is often a waterproof cement or slurry to defend against moisture ingress and subsequent damp problems. Tanking can be be applied to either the internal cellar walls or the external subterranean walls.
External Cellar Tanking
As local water tables rise, earth-retaining walls are often subjected to increased hydrostatic pressure. Hydrostatic water pressure may occur on any wall directly in contact with the earth, therefore there is a need to effectively deal with this pressure to stop water from entering the structure.
An external tanking system prevents water ingress, flooding, and other water damage to a building or substructure by sealing the exterior of the structure to provide a barrier between the building masonry and direct exposure to the ground. Crucially, external tanking prevents moisture from entering through weak joints in the masonry, or through wall floor junctions, to ensure the basement space remains moisture-tight.
External walls can be tanked using a variety of different methods, each using a specific combination of tanking materials depending upon the age of the structure and the ground conditions in which the basement sits. While it is more common to add external tanking to new subterranean structures, depending upon the ground conditions, it can be retro-fitted to existing basements.
Internal Cellar Tanking
An interior tanking system works along similar lines to an external tanking system, but is installed on the inside walls and floor of a basement or cellar. Interior basement tanking is most commonly applied to existing basements, and can be done as a standalone solution or in conjunction with exterior tanking where conditions require. Interior tanking systems are constructed in a similar way to external tanking systems, but have a perimeter drain and sump pump system instead of a land drain to carry water away from the structure.
