Counterflashing

Counterflashing is defined as a piece of metal flashing that is embedded into or attached to a vertical surface such as a wall, chimney, or parapet to overlap and protect the top edge of step flashing or base flashing below it. Counterflashing is typically made from aluminum, galvanized steel, or copper and is installed in a reglet (groove) cut into the masonry or mortar joint. Without counterflashing, water can infiltrate behind the step flashing and penetrate the roof system.