Epoxy DPM and damp-proofing
Moisture is one of the most common reasons a floor coating fails, and it almost always comes from below. A slab that still holds construction moisture, or an older floor with no working damp-proof membrane underneath it, pushes moisture up into the new floor and lifts it off the concrete. An epoxy DPM is the barrier that stops this, letting a resin floor go down on a slab that would otherwise not be ready for months.
Surface Specialists arranges epoxy damp-proof membranes as part of preparing a floor for a new surface. We moisture-test the slab, specify the right system where it is needed and arrange application by experienced specialist contractors, so the floor goes on a sound, dry base. You deal with one point of contact throughout. This page explains what an epoxy DPM is, when a floor needs one and how it is applied.
What is an epoxy DPM?
An epoxy DPM is a liquid-applied damp-proof membrane, a resin barrier rolled or trowelled onto a prepared concrete slab to hold back moisture rising from below. Once cured it seals the surface so moisture in the slab cannot reach the floor laid on top, and it forms the base the resin system or screed then bonds to.
Epoxy DPM, liquid DPM, epoxy resin DPM and surface damp-proof membrane all describe the same thing: a high-performance moisture barrier applied to the top of the slab rather than buried beneath it. That is the key difference from a traditional polythene membrane, which sits under a new slab and is no help at all once a floor is already down. An epoxy DPM is applied to the existing surface, which is what makes it the practical answer on a refurbishment.
Why concrete floors need a damp-proof membrane
Concrete is porous, so moisture moves through it. In a new slab that moisture is left over from construction and takes a long time to dry naturally, often weeks per centimetre of thickness. In an older floor it can be ground moisture rising through a slab that never had a working damp-proof membrane beneath it. Either way, it travels upward and collects under whatever is laid on the surface.
When that surface is a sealed resin floor or coating, the moisture has nowhere to go, so it builds up pressure and lifts, blisters or debonds the floor. The damp patches, bubbling and lifting that follow are not a fault in the coating; they are moisture that was never dealt with underneath. An epoxy DPM removes the cause by sealing the moisture in the slab so the floor above stays sound.
Signs of a moisture problem in a floor
Moisture in a slab often shows itself through the floor laid over it, and the signs are worth knowing because they point to a cause underneath rather than a fault in the finish. The common ones are:
- Lifting or peeling. A coating that debonds and lifts off the concrete, often in patches, as moisture pressure builds beneath it.
- Blistering and bubbling. Raised bubbles in the surface where moisture has been trapped under a sealed floor.
- Damp patches. Dark, persistent damp marks on a slab or coming through a floor finish.
- A floor covering that will not stick. Adhesive failing or a covering that keeps lifting, because the slab underneath is wet.
Where any of these appear, the answer is rarely another coat of the same finish; it is to test the slab and deal with the moisture first, which is what an epoxy DPM does.
When do you need an epoxy DPM?
Not every floor needs one, which is why the slab is moisture-tested at survey rather than assumed either way. An epoxy DPM is typically needed in a few situations:
- New or recent slabs. Fresh concrete holds construction moisture for a long time, and an epoxy DPM lets the floor go down without waiting weeks or months for it to dry.
- Older floors with no working membrane. Many older slabs were laid without a damp-proof membrane, or have one that has failed, so moisture rises freely.
- High moisture readings. Where testing shows the slab is above the level a coating can tolerate, a DPM is specified to suppress it.
- Previous moisture failure. Where a floor has already lifted or blistered, a DPM addresses the cause before a new floor goes on.
The reading from the moisture test is what decides it, so the membrane is used where it is genuinely needed rather than added to every job.
How is an epoxy DPM applied?
The membrane only works over a sound, properly prepared surface, so the slab is mechanically prepared first by grinding or shot blasting and any repairs are carried out. The epoxy is then applied to the prepared surface, usually in one or more coats depending on the system and the moisture level, and left to cure into a continuous, sealed barrier.
Once it has cured, the resin floor, coating or screed goes on top, bonding to the DPM rather than to bare concrete. The membrane can also be applied under a screed where a levelling layer is going down over a damp slab. Because it cures in hours rather than the weeks a slab would take to dry naturally, an epoxy DPM is often what keeps a project on programme.
What to know before you specify a DPM
Test first. The decision rests on a moisture test, so the slab is measured before anything is specified. This avoids both the failure of skipping a needed DPM and the cost of applying one that is not.
Preparation comes first. Like any resin layer, the DPM needs a sound, clean surface to bond to, so the slab is ground or shot blasted and any concrete repairs made good before it goes on. See our sanding and grinding service.
It is part of the build-up. An epoxy DPM is one layer in the floor, between the prepared slab and the finish or screed, so it is specified alongside the rest of the preparation rather than in isolation.
Why choose Surface Specialists?
Getting moisture right is the difference between a floor that lasts and one that lifts within months, and it comes down to testing properly and specifying the right system. That is what we arrange, with one point of contact looking after the project from start to finish.
- A specialist focus. We concentrate on resin and surface treatment, so moisture is tested and the membrane specified to suit the slab rather than guessed at.
- Experienced contractors. Application is carried out by established specialist contractors who deal with damp slabs and moisture suppression routinely.
- Tested, not assumed. The slab is moisture-tested so a DPM is used where it is needed and the floor goes on a base that is genuinely ready.
- One point of contact. From survey through to a prepared, sealed floor, you deal with us.
Epoxy DPM is one of our subfloor preparation services, alongside floor screeding and sanding and grinding. It underpins our commercial and industrial resin flooring. Learn more about Surface Specialists or explore the full range of resin flooring we cover.
Areas we cover
We arrange epoxy DPM and damp-proofing through experienced specialist contractors and are steadily extending the areas we cover. See our areas we cover hub for local detail, including resin flooring in Manchester, with more local pages being added.
Get a quote
Tell us about your floor and what is going on it and we will arrange a free site survey, including a moisture check, then provide a written specification and quotation, typically within 48 hours. There is no obligation. Contact us to get started.
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Frequently asked questions
What is an epoxy DPM?
An epoxy DPM is a liquid-applied damp-proof membrane: a resin barrier rolled or trowelled onto a prepared concrete slab to hold back moisture rising from below. It seals the surface so moisture cannot reach the floor laid on top, and the resin system or screed then bonds to it.
How do I know if my floor needs a DPM?
A moisture test on the slab decides it. New slabs and older floors with no working damp-proof membrane often need one, but the reading is what confirms it. The slab is tested at survey, so a DPM is specified where it is genuinely needed rather than added to every floor.
What is the difference between an epoxy DPM and a polythene membrane?
A polythene membrane is laid under a new slab and is no use once a floor is already down. An epoxy DPM is applied to the top of an existing slab, which is what makes it the practical answer for refurbishing a floor where the moisture problem is already there.
Can an epoxy DPM go under a screed?
Yes. Where a levelling screed is going down over a damp slab, the DPM is applied to the prepared surface first and the screed laid over it, so moisture is sealed in below the new build-up.
Does a DPM save time on a new slab?
Usually a great deal. A new slab can take weeks per centimetre to dry naturally, while an epoxy DPM cures in hours and lets the floor go down straight away, which is often what keeps a project on programme.
Which areas do you cover?
We work through a network of experienced specialist contractors and are extending the areas we cover. Contact us to confirm cover for your project.