Most of the water that enters masonry walls gets in at the parapet, roof, and windows. So it's critical that all these spots be flashed properly. To prevent water damage, the entire masonry wall must be designed as a system. Here are tips for flashing a typical masonry wall from top to bottom. IN THE PARAPET Exposed on both sides, parapets face severe exposure to wind-driven rain. Parapets are thus a primary source of water entering the wall. To prevent water entry, cap parapets with a cast stone, natural stone, terra-cotta, or metal coping. Slope copings so they drain toward the roof. Place through-wall flashing in the bed joint immediately below the coping or metal cap. AT SHELF ANGLES At the roofline, install a shelf angle and flashing to separate the parapet from the wall below. Flashing should also be installed at each shelf angle throughout the height of the wall. Extend the flashing from the backup through the exterior wythe. To allow moisture to escape, in the first course above the flashing install weep holes in the head joints every 2 feet on center. It takes both flashing and weep holes to make the system work. LINTELS AND SILLS Whenever possible, set windows and doors back from the face of the wall. This creates a drip that keeps rain off the sealed joint between the window head and lintel. It also creates a shadow line to hide the flashing. Shed water off sills by sloping them away from the window, but put flashing in the joint below to catch and redirect any moisture that does get in. AT THE WALL BASE A course of flashing at the base of the wall catches all the remaining water that enters the wall and drains it out the bottom course of weep holes.
