Zinsser WaterTite Clear Mold & Mildew-Proof Floor & Wall Paint is a modified acrylic copolymer designed to form an impermeable and very smooth, non-pigmented barrier to water on bare masonry wall and floor surfaces. It is intended for use on interior or exterior, vertical or horizontal, concrete block (not lightweight block) and cast-in-place concrete. It stops moisture from entering or exiting a concrete surface.