Damp Proof Membranes (DPM)

A damp proof membrane (DPM) is a waterproof barrier installed beneath concrete floor slabs, screeds and foundations to prevent ground moisture, rising damp and water vapour from penetrating the floor construction. DPMs are a building regulation requirement in most ground floor construction, providing a continuous barrier between the ground and the floor structure above. They are used across new build housing, commercial construction, basement conversions, extensions and refurbishment projects wherever a concrete floor slab or screed is laid at or near ground level.

Without an effective floor damp proof membrane, ground moisture can rise through a concrete slab and cause damage to floor finishes, insulation, structural timbers and the wider building fabric. A correctly installed DPM protects against moisture ingress for the life of the building.

Polythene damp proof membranes

Polythene sheet DPMs are the most widely used product for concrete floor slab applications. Laid either above or below the concrete slab, they provide a continuous physical barrier against ground moisture and soil gases penetrating the floor construction. Polythene DPMs are available in a range of thicknesses from 250 to 600 micron, with 1200 gauge (300 micron) being the standard specification for most residential floor slabs. Heavier gauges are specified for commercial applications and where the membrane is required to withstand greater loads or site conditions during the construction phase.

When installing a damp proof membrane beneath a concrete floor, sheets should be lapped a minimum of 150mm at all joints and sealed with DPM jointing tape to maintain a continuous seal. The membrane should be turned up at the perimeter and dressed into the wall damp proof course (DPC) to create a complete and unbroken moisture barrier across the floor and wall junction. Care should be taken to avoid puncturing the membrane during concrete pour.

Polythene DPMs are suitable for use in solid ground floors, basement floors, garage floors, extensions and sub-slab applications across residential and commercial construction. Products from Visqueen, Novia, Principle Building Products and ITP are available in rolls to cover large floor areas efficiently.

Liquid applied and bituminous DPM

Liquid applied damp proof membranes provide an alternative to polythene sheet where a bonded, paint-on solution is required. Applied directly to a concrete base or sub-slab as a damp proof membrane paint or bituminous coating, liquid DPMs form a continuous waterproof film that bonds to the substrate and eliminates the risk of puncture during construction.

Bitumen damp proof membranes such as the Sika Black Jack 908 DPM are brush or roller applied directly to concrete floor slabs and foundations prior to insulation, screed or floor finishes. They are particularly suited to refurbishment and basement conversion projects where laying a sheet membrane is impractical due to existing construction, and to applications where the membrane needs to be applied to a concrete base before a new screed or insulated floor system is installed.

Liquid applied DPMs are also suitable for use beneath wood floor heating systems and insulated floor screeds, providing a reliable moisture barrier at the base of the floor build-up.

Choosing the right DPM

For most new build ground floor slab applications, a polythene sheet DPM from 250 to 600 micron is the standard and most cost-effective solution. For refurbishment or where the substrate is uneven, a liquid applied bituminous DPM paint offers greater flexibility and ease of application.

All products in this range are suitable for applications where no hydrostatic water pressure is expected. Where ground water pressure is present, such as in below-ground basement construction, a Type A structural waterproofing membrane or Type C cavity drain system is required. See our Waterproofing Membranes and Tanking range for these applications.

Why Choose Construction Supplies UK for Damp Proof Membranes 

Polythene and liquid applied DPM in one place: From 250 to 600 micron polythene sheet DPM to bituminous paint-on membranes, we stock solutions for ground floors, basement floors, garage floors and sub-slab applications.

Trusted industry brands: Shop leading manufacturers including Visqueen, Novia, Sika, Principle Building Products and ITP, alongside our own Construction Supplies UK brand.

Competitive trade prices: Damp proof membranes supplied at competitive trade prices with no minimum order value.

Fast UK-wide delivery Reliable nationwide delivery with free shipping available on order over £300.

Expert support when you need it Our team can help you choose the right DPM for your project. Get in touch @ sales@constructionsuppliesuk.co.uk or call us on 03300 55 32 02.