Traditionally, an epoxy surface DPM, such as Tremco ES100, has been used where readings are up to 97.9% relative humidity (theoretically 99.9%). Before this can be applied it is vital that the subfloor is surface dry, even and contaminant free. If the surface is not even, pre-smoothing of the subfloor is recommended. This will achieve two things, one, the effectiveness of the surface DPM and two, the correct coverage rate of the surface damp proof membrane.
If the above is achieved, the epoxy DPM can be applied directly to the subfloor followed by a primer and then the smoothing compound. The selected floorcovering is then adhered with a suitable Tremco flooring adhesive.
It’s worth noting that some Tremco smoothing compounds can be applied directly to the Tremco DPM without the requirement of a primer, however, we would strongly advise Installers to always contact the manufacturer for further guidance on this.
NEWBUILD ENVIRONMENTS When readings are up to 95% relative humidity on a new build project, and there is an effective DPM installed under the subfloor, a moisture vapour suppressant can be used, such as Tremco ES600.
Once the subfloor is surface dry, even and contaminant free, two coats of ES600 should be applied. When the first coat is fully cured, a second coat is applied at right angles to the first and allowed to dry.
When the second coat is fully cured (usually one hour), a suitable Tremco smoothing compound should be applied, followed by the recommended adhesive for the floorcovering, completing the project.
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PRIMER CONSIDERATIONS When considering primers, dry substrates may vary in porosity and require priming to prevent any pin-holing from occurring. Self-levelling floor finishes will adhere well on their own, but a primer can still be essential to stop this. This is an important consideration, as otherwise air in the substrate may rise through the self-leveller and cause air bubbles.
A screed or mortar topping will need a primer to ensure a good bond with the substrate, the exception being some water-based polyurethane screeds, which can be applied to cementitious substrates (concrete or screed) without a primer dependent on the condition of the substrate.
Products such as Isocrete Primer, an acrylic, emulsion-based primer for Isocrete cement-based self-levelling screeds, can be used to prime concrete and screed subfloors, as well as impermeable surfaces, prior to the screed application. It improves adhesion to the substrate, reduces surface absorbency and prevents air bubbles migrating to the surface.
In all situations, correct preparation remains essential to success and, in this important area, manufacturers are on hand to help contractors achieve the right outcome.
For more detailed information and best practice, the British Standards, BS8203:2017 Code of Practice for the Installation of Resilient Floor Coverings is an excellent reference.
Tremco can also offer support and guidance to ensure contractors and specifiers make the right decisions.
www.tremco-europe.com SUBFLOOR PREPARATION | 35
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