Cavity Drain Membrane Systems

Based in Brighton, Lewis-Bradbury are Specialist Installers of Structural Waterproofing and Cavity Drain Membrane Systems who cover Sussex, Surrey, Kent and London.

Based in Brighton, Lewis-Bradbury are Structural Waterproofing and Cavity Drain Membrane Systems Specialists who also cover Sussex, Surrey, Kent and London.

Cavity drainage systems or “type C” waterproofing usually utilise pre-formed high density drainage membranes, channels and sumps. These are designed so as to direct any water entering the structure back out in a controlled and managed way. Typically cavity drain membranes are installed to the walls and floors these direct water into drainage channels. The channels then allow water to be directed to sumps or drains so that it can be removed safely from the building. Cavity drain membranes provide an alternative to conventional cementitious tanking systems, which work by holding the water back. Cavity drain membranes work on the principle of allowing water to continue to penetrate the structure but control it in the air gap and divert it to a suitable drainage point. They do not allow pressure to build up against the internal construction and the air gap behind the membrane allows the structure to breathe and to some extent to dry out. The membranes are lose laid on floors and fixed to walls using special plugs and sealing materials, with little or no preparation required to the substrate. Once the membrane has been fitted, wall surfaces can be dry lined or plastered directly and floors can be screeded or a floating dry board system installed.

The typical areas of use are for existing Basement Waterproofing, Cellar conversions, Structural Waterproofing, Barn conversions, Retrofit, New Build, Damp proof membranes and Gas Barriers.


Lewis-Bradbury supplies products and systems designed for cellar waterproofing and other general waterproofing works in new build and existing properties. Key products for waterproofing include Isola Platon cavity drain membranes, which are designed for use in all cellar or basement waterproofing projects to control the ingress of damp or running water. A complete range of Isola Platon polyethylene studded membranes is available which can be specified according to the application and which work on the principle of allowing the damp or running water to travel behind the membrane to a controlled drainage system. Benefits of cavity drain membranes over other damp proofing methods include the minimal disturbance and preparation required to the existing substrate and their toleration of structural movements.


Lewis-Bradbury are specialists in structural waterproofing and basement conversions and are able to consider the nature of the building and the clients design requirements to ensure that the correct method of waterproofing is selected and executed to enable the highest standard of basement conversions.

For more information regarding Cavity Drain Membrane Systems, or to arrange a survey and quotation please contact us