Thompsons One Coat Water Seal Ultra protects against water damage in one coat. The silicone micro emulsion effectively penetrates below the surface of porous materials carrying waterproofing resins deep into the pores of the substrate. The breathable waterproofing membrane allows moisture vapour inside the substrate to evaporate whilst protecting against water penetration & damage. The invisible membrane is protected from ultraviolet light & is long lasting even under heavy moisture conditions. Assuming application instructions & coverage guidelines are adhered to it provides effective water repellency for years in just one coat. 5 Litre.