The layer of waterproof material that keeps water from getting into a building is called flashing. Bitumen, EPDM, aluminum, copper can all be used as flashing materials. Flashing should be installed at rooflines, on the tops of the walls under copings, above windows and doors and below window sills. Properly installed flashing should meet code requirement for "through wall flashing"
Through wall flashing" acts like a large skirt to collect water once the water has penetrated the most exterior portion of the masonry. Then it directs the water to the outside of the building through installed weep holes. The absence of weep holes means there is no way for the water to escape once it penetrates the masonry wall. The absence of flashing means that once water penetrates the exterior wall, it will be directed into the living space.

Proper way to install limestone copings over new flashing		Butuminous flashing with cotton weep cords installation		Roof to parapet wall flashing installation		Properly installed flashing on top of the metal lintel