This ready-to-use, flexible, mold- and mildew-resistant waterproofing crack isolation membrane is for interior and exterior applications. Forms a smooth, monolithic, watertight surface over walls, floors and ceilings. HydraFlex™ Membrane stops in-plane cracks up to 1/4 inches (6 mm) wide at the subfloor from telegraphing through to ceramic and stone tile. For residential to extra-heavy commercial applications.