Most flooring installers are aware that the substrate must be fully cured and have attained the moisture content stipulated by the manufacturer of the floor covering before installing the final floor covering. This is because excessive moisture in the substrate, or high moisture vapour emission rates, will most certainly result in an installation failure, for example, vinyl flooring ‘bubbling’ or delaminating from the substrate.

If there is no damp-proof membrane below a surface bed, or if moisture levels do not attain 3% (75% RH) or less, a suitable moisture, or vapour barrier should be installed such as TAL VaporStop HB. This is not to be confused with a surface sealant, which is applied as a protective layer over a floor substrate or covering.

Manufacturers of floor coverings stipulate moisture levels for their materials, to ensure a successful end result. Ordinarily, 28-days are required for a concrete or sand/cement screed topping to cure and the construction moisture to dry out, prior to installing the floor coverings. However, it can happen that even though the floor surface may appear to be dry at the time of installation, when tested, moisture levels within the surface are higher than the manufacturers recommendations. This can be due to not enough time allowed for curing / drying out of the substrate, or the moisture levels may remain too high because of seasonal fluctuations, changes in geographic surface run-off and structural changes in and around the building. It is therefore recommended that TAL VaporStop HB be installed as part of the installation system, to prevent the passage of water vapour and moisture through the concrete slab into the final floor covering.

Whilst the additional cost may seem an unnecessary addition to the flooring system, the cost of repairing a failed flooring installation far outweighs the costs of the vapour barrier. Using a multi-level system approach when installing floor coverings is key to enjoying a long-lasting and durable installation, and a happy client.

For more information on the value of vapour barriers and on multi-level installation systems for floor coverings, contact the TAL Technical Advice Centre.

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