Liquid DPM is a two-coat epoxy damp proof membrane applied to prepared concrete, suppressing residual moisture up to 98 per cent relative humidity. Supplied as a standalone preparation package to main contractors, priced and programmed to your dates.
Standard epoxy systems tolerate a substrate at roughly 75 to 80 per cent relative humidity. Above that, moisture vapour pushes up through the slab and lifts the coating off it. A new slab can read well above that figure for months while looking completely dry on the surface.
The two situations that produce it are residual construction moisture in concrete that has not finished drying, and rising damp where groundwater migrates upward by capillary action, usually showing as efflorescence or damp patching.
A liquid DPM resolves both. It is a two-coat solvent-free epoxy applied directly to prepared concrete, forming an impermeable barrier that suppresses moisture up to 98 per cent RH. The finished floor is laid over it once the DPM has cured.
Relative humidity measured within the slab rather than at the surface, with the readings recorded so the specification can be evidenced later.
Diamond grinding or shot blasting back to sound concrete with HEPA extraction, removing laitance, curing compounds and contamination.
Solvent-free epoxy applied in two coats to full coverage, with the second laid at right angles to the first so pinholes cannot align.
Left to cure, then either overcoated with the flooring system or handed back to you as a prepared, sealed deck for your own follow-on trades.
Most of our DPM work is a package for a contractor whose slab has failed a moisture test and whose programme has not moved to accommodate it. You are not buying a floor from us, you are buying the deck ready for someone else to finish.
Tell us the window and we will confirm availability on the call. Weekend and out-of-hours working is normal on fit-out programmes and does not need negotiating.
If there is a figure allowed in the package, say so. We will tell you straight away whether it covers the area and the preparation, rather than quoting blind.
Moisture readings, product data and method statements issued as a record, so the specification is evidenced if the floor is ever questioned later.
Moisture vapour trapped under an impermeable coating has nowhere to go, so it pushes upward and forms blisters. It is called osmotic blistering and it does not appear immediately, which is the problem. It surfaces weeks or months after handover, once the area is occupied and in use.
By then the remedy is not a repair. The failed coating has to come off, the substrate has to be tested and prepared again, and the membrane installed that should have gone down first, before the finish is relaid. The second installation costs more than the first and lands at the worst possible moment.
Roughly 95 per cent of resin floor failures trace back to preparation or specification rather than materials, and moisture is the single most common cause on new concrete.
The usual rule of thumb is a day per millimetre of thickness, so a 150mm slab is around 150 days in good drying conditions. In practice it depends on the mix, the temperature, the humidity and whether the building is closed in. A hygrometer test is the only way to know, and slabs frequently read above tolerance long after they look dry.
Yes. A below-slab DPM does not always work as intended. It can be punctured during construction, lapped badly, or simply absent under an older extension. If the readings come back high the barrier is not doing its job, whatever the drawings say.
The DPM has to cure before it is overcoated. In most conditions the follow-on system can be applied the next day, which is why the DPM rarely adds meaningful time to a programme. The delay people fear comes from waiting for the slab to dry naturally instead.
Yes, and it is most of what we do in this area. The membrane is supplied as a standalone preparation package and the deck is handed back for your own flooring contractor to finish. We will still document the readings and the product used for your handover file.
Then that is the first call. We can test the slab and tell you whether a DPM is needed at all. Sometimes the answer is that the substrate is within tolerance and the money allowed in the package is better spent elsewhere.
It suppresses moisture vapour up to 98 per cent relative humidity, which covers residual construction moisture and rising damp through the slab. It is a surface-applied barrier rather than a groundworks solution, so where there is an active water ingress problem the source needs addressing as well.
Area in square metres, the window you need it in, and your moisture readings if you have them. If the dates work we will confirm on the call and follow up with a fixed written quotation.
