Cavity Drain Membranes

Installed cavity drainage membrane

Cavity Drain Membranes


A Cavity Drain Membrane is a vital component of a Type C Waterproofing system. It allows waterproofing engineers to utilise alternative waterproofing methods to traditional cementitious basement tanking systems. A crucial part of the Type C waterproofing process is the selection and application of the correct type of cavity drain membrane.

Usually, Type C Waterproofing methods are preferred by Waterproofing Specialist Designers as refurbishment solutions and are normally installed as part of what is known as a combined system.

A Cavity Drain Membrane is an impermeable, high-density Polyethylene or Polypropylene Membrane, with 2mm, 4mm, 8mm, and 20mm studs attaching it to a wall or floor and forming a cavity.

The space between the membrane and the wall itself is known as a cavity, giving the waterproofing system it’s name.

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How Does a Cavity Drain Membrane Work?

A Cavity Drain Membrane is an internally applied basement wall or floor waterproofing system, based on a range of tough and durable cavity membranes.

As opposed to Type A Waterproofing (or ‘tanking’ as it’s known) which works by stopping water from entering the basement entirely, a Cavity Drain Membrane protects your basement by allowing the water to penetrate your basements walls before allowing other parts of the system to handle the removal of the water.

Once the water has made its way through your walls it is collected by the membrane itself, trapping the water in the space between the wall and the membrane. That water is safely fed into a perimeter drainage channel. The drainage channel then directs the water towards a suitable drainage point, this often being a sump pump system.

After the Cavity Drain Membrane has been fitted, its entirely safe for the membrane itself to be dry lined or plastered over, enabling you to return your basement to a habitable and pleasant place to be.

The Cavity Drain Membrane that Timberwise uses is in adherence to BS 8102:2022, the British Waterproofing standard that must be complied with by law in order to provide waterproofing protection.


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Cavity Drainage Membrane In Conjunction With a Sump Pump

A Cavity Drain Membrane provides a grade 3 or 4 dry environment, making a Cavity Drain membrane entirely suitable for domestic or commercial use. It’s essential that the Cavity Drain Membrane is used in conjunction with a sump and pump facility, and that the sump pump system is maintained throughout its lifetime, otherwise there is a greater chance that it might suffer from a breakdown.

The only situation where a sump pump wouldn’t be needed in conjunction with a cavity drainage system would be where there is passive drainage, otherwise, the sump pump is essential.

You will also find that when Type C Waterproofing is installed it is highly recommended that the basement is fitted with the Cavity Drain Membrane which also has some form of mechanical ventilation installed. This then ensures that the air circulation, within the property, is in accordance with guidelines laid down in the 2005 Building Regulations (Approved Document F), to control the risk of condensation.

Fixings In Cavity Drain Membrane

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The Advantages Of Cavity Drain Membranes

The biggest advantage of a Cavity Drain Membrane is that the fixings that attach the membrane to the wall allow some pressure to be released. The space between the membrane and the wall allows the wall to breathe once the moisture has passed through, and as well as relieving pressure on your walls, you might find that your basement structure dries out to a certain extent.

You also have to consider that a Type C Waterproofing system adds no load onto your structure, or any wall it is connected to. In fact, a Cavity Drainage System is much quicker and easier to install than some of the other basement waterproofing systems, and much easier to repair should there be any problem with the system in the future.

A Cavity Drainage System is flexible, maintainable, easily installed and customised for your basement, and most importantly protected by a guarantee. All of this makes it the system of choice for waterproofing designers.

For More Information

If you are looking for more information about the Cavity Drain Membranes that we provide feel free to contact the Timberwise team on 0800 288 8660 to ask any questions you might have. Alternatively, you can fill in one of our online contact forms or just request a survey online.