What is Tanking a Basement?

What is Tanking a Basement? Will it Solve Damp Problems?

Tanking as its name suggests is the formation of an unbroken waterproof tank to an area of a building which is commonly under ground. The tank is formed by the application of a waterproof material to the walls and the floors of the structure, either internally or externally.

Drained Cavity Underground Waterproofing

An alternative water control that is used to make basements and cellar areas more habitable is something known as drained cavity underground waterproofing. In this method water is allowed to pass through walls and floors into a cavity formed by placing an impermeable membrane to the walls and floor. Drainage channels at floor to wall intersections take the water to a sump where it is pumped out to drainage outlets.

Tanking and Drained Systems should be used in underground situations where dampness and water ingress make the room unusable.

When designing a tanking or waterproofing system consideration should be given to the following three points:

  • End Use
  • Access and Positioning
  • Compatibility

Comparisons of Tanking and Drained Cavity Systems

Drained cavity allows for speedy installation and drying. Preparation of floors and walls is often minimal and the system will accommodate slight movement.

The system lends itself well to the application of insulation and thermal boards which can greatly reduce heat loss and condensation. The downside is that water is still coming into the building, there could be problems if a pump or power failure occurs and sometimes water passing through concrete-type structures can produce a lime-type substance which can solidify and block drainage channels.

Tanking systems produce a tank and prevent the passage of water. Pumps are not usually required and the surfaces are usually hard wearing and resilient. Disadvantages are preparation of walls and floors which can be extensive if a good bond to the walls is to be achieved and if the floor is to stay intact under the pressure of water in extreme situations. Slight movements to the building can cause damage to the system leaving weak points and cracks.

Design and Use

Always use an experienced and competent surveyor. Tell the surveyor what your requirements are, for example;

  • A beer cellar, tool store or garage only requires to be dry and cool
  • An area for storage of archives will need to be dry and a have a low relative humidity to prevent paper curling and decay
  • Conversion of living space must be dry, warm, well ventilated and free from serious condensation problems