• Subfloor Must Be Flat. A flatness tolerance of 1/8" to 3/16" in a 10-foot radius.
• Subfloor Must Be Dry. If a slab tests too high in vapor emission to glue a floor down, consider using a vapor retarder type product, installing a vapor retarder and a plywood sub-floor or using an alternative installation method.
• Slab must be free from non-compatible sealers, waxes, and oil, paint, drywall compound etc.
• For lightweight concrete make sure the concrete is well bonded to the sub-floor. Check for hollow spots, cracks and loose areas.
• Over lightweight concrete (less than 3000 psi), if the flooring adhesive used has a higher shear strength than the concrete, use the Floated Subfloor installation method.
• If the psi of the concrete is unknown, use the Floated Subfloor installation method or contact the adhesive manufacturer.
• Rule of thumb: Draw a nail across the top; if it leaves an indentation, it is probably lightweight concrete.