Whether you’re renovating an older property or finishing a new extension, you no doubt are ready to get your final floor down. Be it LVT or engineered oak, the finish relies completely on the preparation. Here at Top Mix Ltd, we see many homeowners and builders reaching for a bag of floor smoother to solve their uneven subfloor issues.
There is one latent danger, however, that can make your project a failure even before it gets off the ground, and that is residual moisture. Pouring a levelling compound in Oxford directly onto a damp concrete slab is an accident waiting to happen.
In this article, we explain exactly why moisture is the “silent killer” of floors and how we can help you avoid a costly “DPM emergency.”
The Science of Failure: What Happens Under the Surface?
Even though concrete appears solid and dry on the surface, it is actually a porous material that behaves just like a sponge. The problem of persistently rising moisture through concrete via capillary action will come from the ground if the slab has no effective DPM.
When you pour a levelling compound over a damp slab, you effectively “seal” that moisture in. As the moisture begins to try to escape, hydrostatic pressure develops, and three common failures occur, which are:
- Bubbling and Blistering: Trapped air and water vapour cause unsightly bumps in your new floor.
- Delamination: The bond between the compound and the concrete lets go, and the floor “hollows out” until it cracks under traffic.
- Mould and Odours: Trapped moisture beneath impermeable floor coverings, like vinyl, will lead to damp odours and unhealthy mould growth.
How to Know if Your Slab is “Dry Enough”
In the UK, for example, British Standards BS 8203 and BS 5325 say that, in most instances, a subfloor is only ready when its RH is below 75%.
We don’t recommend guessing, as a slab that “looks dry” can still be holding massive amounts of water deep in its core. At Top Mix Ltd, we use professional hygrometers and moisture meters for an accurate reading. We conduct technical site assessments along with the supply of high-quality levelling compound in Newbury to ensure whatever job we touch is built to last, starting with a verified dry base.
The Solution: The “Sandwich” System
If your moisture test comes back high above 75% RH, don’t panic. You don’t have to dig up the floor. We can use a professional “sandwich” method to isolate the damp:
- The Base Layer: We use a moisture-resistant primer or a thin “scratch coat” of compound to veneer the concrete.
- The Liquid DPM: We apply a specialist, two-part epoxy resin membrane. This creates a permanent, waterproof barrier that stops rising damp in its tracks.
- Final Level: When the DPM is cured, we pour the final levelling compound to produce a completely levelled surface that is 100% isolated from the ground moisture below.
Why You Should Never Skip the DPM
Saving a few pounds by omitting the damp-proofing stage might seem tempting, but a floor failure costs many, many more times that amount. Ripping up ruined LVT and grinding off failed compounds before starting all over again often can be triple the price of doing it right in the first place.
Let Us Take the Stress Out of Your Subfloor
Here at Top Mix Ltd, we provide more than just the materials. We provide expertise so that your house renovation is truly successful. Contact us to protect your investment.