Custom Building Products RedGard Waterproofing & Crack Prevention Membrane – 1 Gallon is a ready-to-use liquid-applied membrane that provides waterproofing and crack prevention for tile and stone installations. It forms a durable, flexible barrier to protect substrates from moisture while helping reduce crack transfer. Ideal for floors, walls, showers, tubs, countertops, and other interior and exterior applications before tile or stone installation.