Damp Proof Membranes

Damp proof membranes are essential for preventing moisture from rising through concrete, screed or masonry. They form a protective layer beneath floor coverings, helping prevent damage caused by water ingress or residual humidity. This is critical in properties without a proper DPC or where fast track construction doesn’t allow the full drying time of subfloors. These membranes are suitable for both ground floors and below-ground walls.

Liquid-applied systems offer seamless protection and are ideal for complex layouts or irregular surfaces, while sheet membranes provide consistent coverage across large flat areas. Building supplies are chosen based on substrate condition, application environment and drying requirements. Whether used in homes, public buildings or industrial premises, they help extend the service life of flooring and reduce the risk of costly repairs. For best results, pair membranes with compatible primers and coatings from professional-grade building ranges.

Damp Proof Membranes FAQs

Can damp proof membranes be used on timber floors?

Yes, many liquid damp proof membranes are compatible with timber floors, provided the surface is dry, stable, and structurally sound. It’s essential to ensure no movement or flexing is present, as this could cause cracking or detachment once cured. Some systems may require a primer or a reinforcing layer to improve adhesion and accommodate minor movement. Always check the product’s technical data sheet for suitability on wood substrates.

How do I know if my floor needs a damp proof membrane?

A moisture test using a hygrometer or calcium carbide test can determine if a surface is dry enough for coatings or coverings. If the relative humidity exceeds 75%, a membrane is usually recommended. New concrete or screeds that haven’t fully dried, or older buildings with no existing DPM, often need one. Skipping this step risks adhesion failures, trapped moisture and costly repairs.

What is the difference between liquid and sheet membranes?

Liquid membranes are applied with brushes or rollers and form a seamless layer, ideal for uneven or complex surfaces. Sheet membranes, such as polythene rolls, are quicker to lay on large, flat areas and offer consistent thickness. Liquids are often preferred in refurbishment or when moisture readings are borderline, while sheets suit dry, level bases. Your choice should depend on substrate condition, time, and project scale.

Are these products safe to use in residential homes?

Yes, most modern damp proof membranes are formulated with low odour and low VOC content, making them suitable for use in occupied buildings. Ensure rooms are well-ventilated during application and follow all PPE and handling guidelines. Water-based membranes are especially well-suited for use in homes, schools and healthcare settings due to their safer formulations and easier clean-up.

Do I need to use a primer before applying a DPM?

In many cases, yes. Primers improve adhesion to dusty or porous surfaces like concrete and screeds. They also reduce the risk of pinholes and uneven absorption, which can affect membrane performance. Some two-pack DPMs incorporate priming qualities, but always check manufacturer guidance. Using the correct primer can also help achieve the correct film thickness on the first coat.