BIOKIL 3mm Waterproof Membrane Roll – Cavity Drain Tanking System 40m²

The Biokil 3mm Cavity Drain Membrane is a high-performance waterproofing solution designed to protect walls and floors from water ingress. Manufactured from durable HDPE, this studded membrane forms part of a Type C cavity drain system in accordance with BS8102:2009, allowing water to be controlled and safely managed rather than resisted.

Ideal for basements, cellars, and below-ground environments, this membrane creates a dry, habitable internal space with minimal preparation and no drying time, making it suitable for both professional contractors and DIY waterproofing projects.

Key Features & Benefits

• 3mm studded cavity design – controls and manages water ingress
• Type C waterproofing system – compliant with BS8102:2009
• Quick and easy installation – minimal surface preparation required
• No drying time – decorate immediately after installation
• Flexible membrane – easily folds around windows, doors, and corners
• Durable HDPE construction – long-lasting and robust
• Salt inhibiting – protects against salt contamination
• Root and contaminant resistant – suitable for aggressive environments
• Wide temperature tolerance – performs from -50°C to +80°C
• Non-invasive system – minimal disruption to existing structures

Typical Applications

• Basement and cellar waterproofing
• Below-ground structures
• Walls and floors in damp environments
• Vaults and tunnels
• Refurbishment and new-build projects

How the System Works

The studded design creates a cavity between the membrane and the substrate, allowing water to pass behind the membrane and be directed into a drainage system. This prevents moisture from entering internal finishes and ensures a dry, usable living space.

Unlike traditional tanking systems, which attempt to block water, this cavity drain system manages water safely, reducing long-term risk of failure.

Installation Overview

• Fix membrane to walls using Biokil Plaster Plugs or Brick Plugs at max 600mm centres
• Drill through studs and secure plugs with a rubber mallet
• Overlap joints by at least two stud rows (three in severe conditions)
• Seal joints using Biokil Sealing Tape and Sealing Rope
• Install on floors beneath insulation or screed systems
• Finish with plasterboard, render, or stud wall systems

Surface Preparation

Ensure surfaces are sound, level, and free from loose material. Remove any unsound plaster, render, or screed and repair using a suitable sand-cement mix.

Where mould or fungal growth is present, treat surfaces with an appropriate masonry biocide before installation. In above-ground applications, it is recommended to address moisture at source using a damp-proof course system prior to installation.

Aftercare & Ventilation

The membrane creates a dry internal environment; however, effective condensation control is essential, particularly in basements and high-moisture areas.

Mechanical ventilation is recommended to ensure proper airflow and prevent moisture build-up.

Technical Specifications

Why Choose Biokil 3mm Membrane?

This membrane offers a reliable and long-term waterproofing solution by managing water rather than resisting it. Its ease of installation, durability, and compliance with recognised standards make it an ideal choice for both residential and commercial waterproofing projects.

Whether you are converting a basement or protecting a property from damp, the Biokil 3mm Membrane provides a proven, professional-grade system.