For use prior to the installation of ceramic tile, natural stone, resilient flooring, carpet, wood and parquet. Can also be applied to concrete, Wonderboard and cement backerboard, sheet vinyl, PVC, concrete terrazzo, and stone. Can be applied up to 1" thick. ASTM rated for ceramic tile installations over wood subfloors with joists up to 24" o.c. Controlled cured technology eliminates installation problems of bond failure, crumbling, mildew and staining of resilient flooring due to free-moisture. Moldguard technology resists mold and mildew growth. One 50 lb (22.68 kg) bag mixes with 6-3/4 qts (6.1 L) of water.