Purchase this product online ALSAN Flashing is a unique polyurethane bituminous resin specifically formulated for liquid-applied flashings, details and maintenance applications. ALSAN Flashing utilizes a reinforcement that, in combination with its unique chemistry, provides an extremely durable and easy to apply flashing solution. The variety of suitable substrates, including concrete, masonry, wood, metal, granule and sand surfaced Modified Bitumen membranes and PVC pipe.