If water is leaking through existing masonry or you need to protect new construction, DRYLOK Extreme Masonry Waterproofer's proprietary formula is GUARANTEED to stop water. Unlike ordinary paint that simply adheres to a surface and can be forced off by incoming water pressure, DRYLOK Extreme Masonry Waterproofer actually penetrates the pores in that surface, bonding to the masonry and creating an impenetrable barrier. You can use it to waterproof interior, exterior, above or below grade walls including basements, retaining walls, and bare concrete swimming pools, foundations, and more. The breathable film will not trap moisture in the masonry. It is guaranteed to stop water and withstands 15 pounds of hydrostatic pressure (PSI), equivalent to a wall of water 33 feet high.