Zinsser WaterTite Clear Mold & Mildew-Proof Floor and Wall Paint forms an impermeable, very smooth and non-pigmented barrier to water on bare masonry walls and floor surfaces. Use on interior or exterior, vertical or horizontal, concrete block surfaces and cast-in-place concrete. Backed by a 5-year waterproof and mold & mildew proof paint film guarantee, it stops moisture from entering or exiting concrete surfaces.