Flashing

Flashing is defined as thin pieces of impervious material, typically galvanized steel, aluminum, or copper, installed at roof transitions, penetrations, and intersections to prevent water from entering the building envelope. Common flashing locations include valleys, chimneys, skylights, vent pipes, dormers, and wall-to-roof junctions. Improper or deteriorated flashing is widely considered the most common cause of roof leaks.