Additionally, another moisture barrier or retarder should be placed on top of the slab before installation. Low end PVC vinyl applied over the slab in multipurpose adhesive with seams sealed and the surface prepared before spreading the wood adhesive. The use of this method requires dependence upon the water-soluble, multipurpose bond in the presence of moisture and wood adhesives that are accepted over vinyl. This may also require a vinyl blocker. After about 30 minutes, during which the solvents flash or evaporate, the polyfilm can be rolled over the mastic by walking over the film, embedding it in the mastic.
Air bubbles that form under the film can be forced out toward the seams with a push broom.
15-pound roofing felt in asphalt mastic applied with a notched trowel at the rate of 50 square feet per gallon. A second similar coating of mastic and asphalt felt should be added, with overlaps staggered to achieve a more even thickness. There are several other moisture barrier systems available, including two-part epoxy, rubberized electrometric membrane, and other sealing liquids. In all cases, installers must verify acceptability of a particular system with the flooring manufacturer, and also verify adhesive compatibility when planning to glue down over any moisture barrier. If you are not familiar with the system, check with the adhesive manufacturer, the flooring manufacturer and the manufacturer of the moisture barrier system before attempting an installation.