How To Install Cavity Drainage Waterproofing

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Cavity Drainage Membranes System

Cavity drainage membranes are a popular method of basement waterproofing.

They work by internally lining a basement and diverting any water that enters the basement structure into a drainage system.

Cavity Drainage Membranes are classified as Type C waterproofing by the British Standard for waterproofing BS8102:2009.

The first element of a cavity drainage system is providing accessible and maintainable drainage in the slab. This can be provided by the use of Delta Perimter Drainage Channels or by the use of a modular drainage system.

Although it can be possible to discharge this drainage by gravity. Cavity drainage systems should not be connected to a combined sewer due to the risks of smells and sewer surcharge.

Typically a sump pump is used such as the Delta V3 Dual which is suitable for basements up to 100M2 and an invert height of up to 3 metres.

Before the cavity drainage membrane is installed new concrete should be pre treated using Koster Polysil TG500. This is an anti free lime treatment that will prevent the formation of limescale in the drainage system.

For the walls Delta MS500 is mechanically fixed using Delta Qwikseal Plugs. Typically this is fixed at 600mm centres to allow for easy fixing of wall lining systems.

​For the basement slab Delta MS20 is typically used, this has a much better drainage capacity due to the 20mm stud height and can be loaded to 150kn/m2.

The membranes are sealed using Delta Tape and Delta Corner Strip to provide a vapour barrier.