One component waterproof primer for priming porous and non-porous subfloors and for rigidifying soft subfloor surfaces. WAKOL PU 280 Moisture Barrier is a premium moisture barrier for “green” concrete slabs and for concrete and offers two levels of moisture protection: One coat will block moisture up to 12 lbs / 1000 sq. ft. / 24 hour or up to 90 % RH (ASTM F 2170-02). Two coats will lock moisture up to 18 lbs / 1000 sq. ft. / 24 hours (Calcium Chloride Test) or up to 98 % RH (ASTM F 2170-02). WAKOL PU 280 Moisture Barrier may be used on radiant heated floors up to 6 pound / 1000 sq. ft. / 24 hours or up to 85 % RH (ASTM F 2170-02) prior to laying wood flooring.