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 hours or up to 90 % rH (ASTM F 2170-02). Two coats will block moisture up to 18 lbs. / 1000 sq.ft. / 24 hours or up to 98 % rH (ASTM F 2170-02). No moisture test required if the following conditions are met: The concrete must be surface dry, at least 28 days old, a surface temperature of ≥60°F, and must have an intact structural waterproofing membrane beneath the slab. WAKOL PU 280 Moisture Barrier may be used on radiant heated floors up to 6 lbs. / 1000 sq.ft. / 24 hours or up to 85 % rH (ASTM F 2170-02) prior to laying wood flooring.