DPM Membranes for Concrete Floors

DPM Rolls and sheets

These low-density polythene DPMs from Capital Valley Plastics are designed to prevent moisture and gas from the ground entering a property. These DPM sheets create a barrier between the subbase and concrete slab or screed.

1200 Gauge DPMs

We stock 1200 gauge DPMs with the recommended thickness of 300μm - they are highly effective at preventing moisture from passing from the ground into the property. This provides long term protection for any floor coverings such as carpets, laminates or vinyl tiles.

• 1200 Gauge DPM - 4m x 25m
• 1200 Gauge Handy Pack - 4m x 5m - convenient for smaller jobs

These black DPM membranes are unaffected by groundwater and interstitial condensation should it occur. Capital Valley DPMs are also extremely durable and highly puncture-resistant. This means they provide decades of protection as well as withstanding site traffic during installation.

Radon DPM - 1600 Gauge

When it comes to protecting a property from ground gases, you need to opt for the correct radon or general gas DPM, to suit the type of gas:

• Radbar 1600 gauge DPM
• Our full range of gas membranes

These DPMs are specifically designed to stop the transmission of ground gases as well as damp, protecting inhabitants and providing peace of mind.

Read our guide to installing gas membranes.

What is a DPM for concrete floors?

DPM stands for damp proof membrane. DPMs for concrete floors are plastic sheet membranes that are installed before insulation or a concrete slab or screed is poured. It acts as a barrier stopping moisture and contaminants entering the screed and potentially affecting anything installed above. There are different thicknesses of DPMs for concrete floors - 1200 gauge is the minimum requirement.

When can a DPM be installed?

1200 Gauge DPMs should be used when a new screed or concrete slab is going to be laid on hardcore or a subbase. Protecting a new screed or slab will prevent damage to all final floor finishes installed on top such as timber floors, tiles, laminate flooring and carpets.

The black DPMs can also be used in conjunction with underfloor heating systems - under normal operating conditions this will not adversely affect the membrane. In fact, having a dry slab will make the underfloor heating system more efficient.

DPMs in construction

A DPM is an essential component in the construction of a new floor. DPM membranes are laid under a new concrete slab to prevent moisture transmission. In most common construction scenarios, you will have a bed of hardcore with a sand blinding on the ground then either:

• a DPM before a layer of concrete
• a DPM before a layer of insulation then a second DPM before the concrete slab is laid

If you suspect the groundwater to contain sulphates, then the DPM should always be placed below the concrete. Similarly, with suspected ground gases opt for a radon-proof 1600 gauge DPM or a membrane that covers multiple gases if radon isn’t the only gas present.

DPMs above the screed

In some cases it is necessary to install a DPM above an existing screed. This may be where the original DPM was not installed or the original DPM was damaged at some point. In these instances we suggest the use of Liquid DPMs, Epoxy DPMs or even dimpled sheet DPMs. All of these options create a new DPM on top of the concrete screed and protect further coverings from damp and vapour.

• PermaSEAL Floor 1
• PermaSEAL 3
• PermaSEAL 3 ECO Floor
• PermaSEAL Liquid DPM
• PermaSEAL Epoxy DPM
• PermaSEAL PRO One Coat DPM

DPM Installation

DPM installation is relatively straightforward. Roll out the DPM sheet across the surface and cut to size. We recommend that you install the DPM membrane with as few joints as possible so pre planning is a good idea. You should pay particular attention to overlapping and joining with subsequent DPM rolls and make sure these joints are water tight.

It’s vital to avoid any tears or damage during installation as this can create a vulnerability that leads to moisture ingress/ damage. As mentioned before, the membranes can withstand some light traffic but care must always be taken and a final inspection for damage undertaken before any pouring or subsequent coverings.

DPM Tapes 

When DPMs overlap you should use DPM tape to seal the joints. We sell both single and double sided DPM tape. Your DPM always needs to be continuous with the damp proof course (DPC) in the walls etc. When installing a gas-proof DPM, joints should be bonded together with PermaSEAL Double-sided Jointing Tape and sealed with single-sided Tape.

Benefits of DPM

Installing a DPM in the concrete slab helps protect your flooring from moisture transmission. Under normal conditions, the 1200 gauge DPM will remain an effective moisture barrier for the life of the concrete slab. Capital Valley Plastics pride themselves on the durability of their membranes.

Permagard – over 35 Years’ Experience in DPMs

If you have any questions about which DPM is best to use or installing a DPM then contact our expert team on 0117 982 3282. Our technical advice is free and designed to give you the confidence you need to get the job done.

If you are looking for Liquid Epoxy DPMs, Gas Membranes or Wall Damp Proofing Membranes then follow the links to browse our ranges.