Technical Information

The cavity drain system is one of the most commonly used methods of controlling water in basement projects. The cavity drain channel is utilised in association with the installation of a cavity drain membrane to the walls and floors. The cavity drain channel would generally be laid around the ‘perimeter’ of the basement at the wall / floor junctions, this carries the water to the sump chamber where it is collected and discharged using a sump pump or gravity system to an external drainage point.

The sump chamber is installed below the finished floor level. Pipe work to carry the excess water and electrical wiring for the sump pump is fitted in ducting before the concrete is poured.

Prior to the installation of the new concrete base to the basement or cellar floor, suitable provision must be made for the installation of the drainage channel. This is normally achieved via the temporary installation of suitable size timbers or polystyrene etc being placed at the wall floor junctions where the cavity drain channel is to be placed. Once the concrete is laid and set, these temporary formers are removed to enable the installation of the cavity drainage channel.

Section of the drainage channel

The drainage channel is laid and connected to the sump chamber prior to the cavity drain floor membrane being laid. The cavity drain membrane is 3, 8 or 20 mm in depth dependant on the water flow being controlled in the area.

In REFURBISHMENT PROJECTS the system is installed exactly as above following excavation and removal of the original floor etc.

The cavity drain system can be designed to suit various property layouts or building designs, on occasions various factors may result in a variation to the specification detailed above. Additional provision must also be made for flushing out / future maintenance of the system.

One of the range of Cavity Drain Membranes

Within the PLANS & DRAWINGS section of the website there are numerous cross section drawings detailing the above system.

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A basement conversion is always a good idea, especially if you want to extend your living space. See our case study on basement conversion.