Basement / Cellar Waterproofing
About Waterproofing
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Basements are making a comeback: as building plots are getting smaller and more expensive, builders and homeowners are seeing the sense of creating more space from the same footprint.
The key to a successful outcome is basement waterproofing, which will protect against water entering the structure and allow you to create additional living space, leisure facilities or car parking. Without waterproofing your basement, you risk water getting in and causing damp-related and structural issues.
There are 3 different types of waterproofing:
Type A: Also known as tanking, where a barrier system is applied internally or externally to the walls and floor of a structure;
Type B: An inbuilt characteristic of the structure by adding waterproofing additives to the concrete used to form the walls and floor;
Type C: The use of cavity drain membranes, where the aim is not to prevent water entering the structure but to manage it and divert it to a pumping chamber or external land drain.
What’s the difference between basement tanking and waterproofing?
Basement waterproofing covers all methods of waterproofing (BS 8102:2009 Types A, B and C), whereas basement tanking refers only to the application of a membrane or coating to act as a barrier.
Tanking a basement is what BS 8102:2009 refers to as Type A waterproofing. Here, a membrane or coating is externally or internally applied to walls and floors to create a protective barrier and prevent ground water from entering the building.
Basement waterproofing is required when a structure or property, or part of a property, is built at ground level or below. It is likely that there will be a build up of water in the ground surrounding the basement, raising the water table, leading to hydrostatic water pressure.
This water pressure is exerted on the floor and walls of the basement and can lead to water penetration through cracks, joints and structural weaknesses in the basement. Without basement waterproofing, this water ingress can then lead to mould, decay, structural problems and other damp-related issues.
Basement Waterproofing Methods
Basement waterproofing can be achieved in two ways, either by blocking the passage of water into the building with external waterproofing or tanking waterproofing. Or you can control the ingress and flow of the water to a pre-determined evacuation point by the use of cavity drainage systems.
Basement Tanking
Cementitious tanking materials are used for basement tanking when there is a requirement to block water ingress into the building. After preparing the surface, the basement tanking slurry is applied to the masonry surface in two to three coats depending on the volume of water ingress. The basement tanking slurry then cures to form a water impermeable surface which should then be covered with a render to protect it. By using this basement tanking method, the basement remains completely waterproof and the walls remain dry and breathable.
Basement Membranes
Basement tanking membranes like PermaSEAL and those manufactured by John Newton and Platon, are designed to control the passage of water using cavity forming membranes, drainage channels and sump and pump water evacuation systems.
Newton Membranes and PermaSEAL Waterproofing Membranes come in a wide variety of sizes and types. Some membranes have a mesh welded on the face for direct rendering or for fixing dot and dab plasterboard systems. Other basement tanking and basement waterproofing membranes are plain, designed for flooring or where a wall is to have a dry-lining finish.