a masonry flashing is disclosed having a polymeric membrane and a pressure - activated adhesive in a peel - and - stick product . the flashing is used in cavity walls , typically a wall with an inner wythe of masonry block and an outer wythe of brick . the adhesive layer is a hot melt with various additives , which additives provide reinforcement to the flashing structure . the reinforcement can be fiber glass or filamentous fragments of polypropylene that are admixed into the adhesive . the flashing has a release sheet and , after removal thereof , the adhesive is pressed against the rough surface of the masonry block creating a durable bond with the inner wythe . incorporated into the masonry flashing are various high - strength , polymeric webs including a spun - bonded polyolefin , an ethylene propylene diene terpolymer , and a polyvinylchloride with an ethylene interpolymer .