Wykamol CM8 Cavity Drain Membrane

The Wykamol range of cavity drain membranes are high quality, structural
waterproofing materials, with a choice of stud height for different drainage capacities and applications.

product length 

2M X 20M

What Is the Wykamol CM8 Cavity Drain Membrane?

The CM8 is a cavity drain (or “tanking”) membrane system manufactured by Wykamol. It’s made from High-Density Polyethylene (HDPE) with 8 mm studs that create a drainage cavity next to walls/floors. The studs keep the membrane off the substrate, allowing water to flow behind the membrane into drainage channels or a sump & pump system.

Key Features & Technical Highlights

• Studded HDPE design: 8 mm studs create a drainage cavity behind the membrane.
• Waterproof, salt‑inhibiting, root & contaminant resistant: Protects interior finishes from moisture and harmful salts.
• Rapid installation: Requires minimal surface preparation (e.g. walls/floors don’t need to be perfectly smooth), can be cut with a sharp blade.
• Immediate option to finish: No long drying time needed; after installation, finishes can be applied immediately (e.g. plasterboard, render) especially with the mesh version.
• Thermal & mechanical stability: Built to tolerate both low and high temperatures, movement, stresses behind the membrane.
• Compliant with BS standards: It is part of Type C cavity drain membrane systems per BS 8102, delivering Grade 3 (or higher) dry / habitable environment where correctly installed.

Advantages / Benefits

• Transforms wet or damp walls/floors into habitable, dry spaces.
• Minimises damage to the existing structure: less invasive than full external excavation or thick tanking plaster
• Flexibility: easier to work around corners, windows, doors, etc. Mesh version allows direct finishes.
• Durability: robust against water pressure, salts, roots, contaminants. Long life when those manufacturer’s instructions are followed.

TYPICAL USES
Walls, Floors, Vaults, Tunnels, Above and below ground level, Waterproofing applications and Damp-proofing applications.

SUBSTRATE PREPARATION
1. When used in new construction, the concrete slab must be laid in accordance with BS 8204-1:2003+A1:2009 to achieve a flat surface not deviating more than 5 mm from the underside of a 3000 mm straight edge.

2. Unsound plaster, render or screed should be removed and surfaces made level, with floors to the above tolerances. This can be achieved using Wykamol’s Universal Mortar, or a 3:1 sand: cement mix incorporating Render proof Waterproofing Additive. Leave all new works to dry thoroughly before CM8
membranes are fixed.

3. In case of walls suffering from mould or masonry fungi, prior to fixing the membrane, remove surface contamination by brushing, then apply Microtech Biocide in line with the relevant Technical Data Sheet.

4. If dry rot (Serpula Lacrymans) is present in the walls, this will require detailed assessment before proceeding.

5. Above ground level it is recommended, that where possible, all sources of moisture are alleviated at the source using a DPC such as Ultracure, before applying CM8 membrane. This reduces potential damage to masonry and timber etc.

6. Ensure flanges run vertically on walls and are positioned in front of the preceding width of membrane. In the case of horizontal joints, the lower sheet is positioned to the front.

7. Where there is or could be severe water ingress, joints may also be closed off with Wykamol Overseal Tape.

8. Seal the stud to stud joints with Wykamol Rope