It is important to install flashing at the parapet in two key locations: 1) under the coping stone, and 2) at the roof line. Installation of flashing under the coping stone prevents water infiltration at joints in the coping stone. Installation of flashing at the roof line can prevent warm moist air from the lower wall filling the parapet cavity. The parapet will go through more freeze-thaw cycles than lower walls as parapets are exposed on both sides. Particularly in cold climates, the moist air in the parapet will cause significant freeze-thaw damage.
Parapet Flashing Types
Flashing materials include sheet metal (copper, galvanized steel, stainless steel, aluminum, lead), EPDM (ethylene propylene diene monomer rubber), plastics and asphalt impregnated membranes. Self-adhesive membranes are popular with many masonry designers and provide adequate durability for many applications. Copper, stainless steel, and lead flashing are used in buildings where the designed service life is measured in hundreds of years.