Engineered Wood Flooring on Concrete Slab and Over Underfloor Heating Systems – Installation Recommendations

Upon delivery to the job site, the engineered hardwood flooring should be checked on the top wear layer for moisture content, due to job site possible changes in humidity during transport. Moisture content should be between 6% & 9% to be considered normal.

If necessary, acclimatize the flooring for 3 – 5 days under normal room conditions prior to installation. Inspect each board carefully for any defects before installing them.

No painting or drywalling should be done while the hardwood floor is stored or being installed, since these can contribute to an increase of the humidity in the air.

In order to properly install hardwood flooring on concrete, the slab must have cured for at least 30 to 45 days. Prior to installation, a concrete moisture test must be performed using a moisture meter, such as a RAPID RH MOISTURE METER. In order to proceed, the moisture content of the concrete must be less than 12%. Alternatively, a poly test could be used to test an area of 1 square foot.

The concrete surface where the flooring will be installed should be levelled and clean (free of any dirt or debris). The maximum unevenness tolerance allowed is 3/16” in 8 Ft radius.

Moreover, the concrete slab should be smooth to allow full contact of the planks to the subfloor. If the concrete surface is not level or smooth, a levelling compound may be used to correct the problem. However, it is crucial to ensure that this compound is completely dry before installing the hardwood flooring. Therefore, another concrete moisture test must be performed, before proceeding with the installation.

It is recommended to use the proper flooring adhesive to install engineered wood flooring, which should be full glued down directly onto the concrete sub floor.

In condominiums, it is mandatory to use a sound underlay underneath the wood floor in order to prevent sound to disturb residents of the units below. This sound underlay should meet the Condo Board requirements and must be suitable for full glue down installations.

This process is what is called Double Glue Down installation; first the sound underlay is glued down to the concrete slab and then the hardwood floor is glued down to the sound underlay.

On full glue down installations, the adhesive should be applied directly to the sub floor in sections of no more than 2 or 3 boards wide in order to avoid pushing the glue up and into the tongue and grove of the flooring. Needless to mention that the trowel recommended by the adhesive manufacturer should be fully respected.

If needed, use clamps to keep boards tight. Weights may be placed carefully on top of the installed boards to help with adhesion where there is minor unevenness in the concrete sub floor. These weights should be removed as soon as possible to avoid damaging the flooring.