Thompsons Water Seal utilises hydrophobic technology to deliver invisible protection against water damage. The deep penetrating formulation travels deep into exterior dry porous surfaces to form a breathable membrane that allows moisture vapour inside the substrate to evaporate whilst protecting against water penetration & damage. Thompsons Water Seal has a unique formulation which, unlike some water-proofers, penetrates the surface therefore waterproofing even after the initial beading is gone. It will not be destroyed by ultraviolet light & is long lasting even under heavy moisture conditions. Assuming application instructions & coverage guidelines are adhered to it provides effective water repellences for years. Suitable for use on brick, concrete, stone & wood. For exterior use only.