Custom Building Products RedGard Waterproofing & Crack Prevention Membrane – 3.5 Gallon is a ready-to-use liquid-applied membrane designed to provide waterproofing and crack prevention for tile and stone installations. It creates a durable, flexible barrier that helps protect substrates from moisture while reducing the transfer of cracks. Ideal for use on floors, walls, showers, tubs, countertops, and other interior and exterior applications before installing tile or stone.