Air & Vapor Barrier 1800 provides a seamless and continuous membrane around the building envelope. It is watertight and impermeable to air and water vapor, and forms a seal around penetrations and brick ties. The solvent-based rubber polymer can be sprayed directly onto exterior drywall, concrete block, and even damp concrete. It dries within 12 hours and can withstand up to 30 days of UV exposure. Mar-flex Building Solutions.