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Flooring moisture should be no barrier to quality flooring

A flooring moisture barrier is key to quality, high-performance flooring.

It’s particularly pertinent when installing a resin surface, a process that can be severely hampered if a substrate beneath an existing surface is damp.

In such instances the obvious solution would be to break-up and replace the substrate and risk adding considerable project time and cost.

Slab-Sika Moisture ControlA moisture barrier – in the form of a liquid solution which is applied to a slab – offers a simple, rapid, less labour-intensive alternative to ripping-out the old surface.

First things, first: for a high-quality resin floor installation, the moisture level of the substrate beneath shouldn’t exceed 4% by weight when using a Tramex meter.

This can be gauged with a Tramex moisture meter, an effective testing method to ascertain a screed’s suitability for a resin finish.

The size of a standard calculator, the moisture meter comprises probes that are pushed onto the floor, and a gauge that measures the substrate’s moisture content.

Depending on the area of the slab, it’s recommended multiple readings are taken to give an accurate representation of its moisture content. 

Be precise about Flooring Moisture

For an alternative method, the calcium carbide test is advised.

It involves taking core samples from a concrete floor which are crushed and mixed with a chemical compound – calcium carbide.

The process takes a few minutes per concrete sample, but it’s considered to be a more accurate moisture reading method.

Attaining an accurate substrate moisture reading is essential for a resin floor’s long-term performance.

Concrete and screeds which exceed the 4% moisture level will result in the resin floor to de-bond or suffer osmosis: floor ‘blisters’ caused by escaping moisture.

Sika-Subfloor-Moisture-ControlSome manufacturers will have the solution to eliminate such issues, in the form of a guaranteed temporary moisture barrier that can also be used as a self-smoothing floor screed.

The systems can be three-part, epoxy-modified, cementitious, fine textured mortar and comprise a moisture-tolerant primer.

The primer allows moisture to pass from the substrate to the temporary moisture barrier which scavenges the excess moisture lowering the percentage to <4% by weight, leaving a resin-ready surface.

With preparation complete, the moisture barrier must be applied to a minimum 2mm thickness and allowed to cure for around 24 – 48 hours depending on the substrate temperature, before being over-coated with a vapor tight seal coat.

In the case of Sikafloor®-81 EpoCem®, a three-part, epoxy-modified cementitious mortar which can be used as a temporary moisture barrier, the substrate temperature should be a minimum 8°C before it is installed.

Economical, fast and easy to apply, the genius of a good moisture barrier is its superb ability to remain liquid resistant, yet permeable to water vapour.

It is worth pointing out that manufacturer product sheets should be checked regarding these details as they may vary slightly from product to product. 


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