CP-500W is a spec grade water based silane / siloxane water repellent. It penetrates and reacts with the silica in concrete and masonry in the presence of ultraviolet light and atmospheric moisture. This reaction forms a strong hydrophobic bond beneath the surface that prevents water molecules from penetrating, while allowing free migration of water vapors. The chemical bond formed in this process allows CP-500W to become an integral part of the substrate and provide long-term protection. CP-500W can be used on most vertical or horizontal, exterior, above-grade surfaces. Coverage rates vary from 50-250 sq. ft. per gallon, depending on surface porosity and texture.