Masonry Magazine March 2012 Page. 34
MOISTURE MANAGEMENT
water that bypasses the flashing will very likely result in an active water leak in the occupied space below (see Figure 3). The wall cavity must not be blocked with mortar droppings, and the flashings and weeps must be very well constructed at these locations.
At the base of walls, a sheet metal flashing assembly that extends from the face of the backup wall through the masonry should be used to form a drip outside the wall. A sheet waterproofing membrane or water-resistive barrier is utilized to flash over the back leg of the metal flashing (see Figure 4). Weeps are provided through the masonry veneer. A manufactured, mortar-control device is used to catch droppings at the base of the drainage cavity so that they can not block the weeps. The open cavity below the flashing should be filled so that there is a solid backing under the flashing at laps. This action helps prevent the bottom piece of flashing from deflecting downward as the lap seam is created.
There are critical components of this detail that should not be overlooked, such as lap joints, expansion joints, door thresholds, and inside and outside corners.
Shelf angles
SOMETIMES CALLED relieving angles, these are locations where a structural angle is provided to carry the dead load of the masonry veneer. Buildings often incorporate continuous shelf angles that support the masonry veneer at heads of windows. Shelf angles are also found at floor lines of taller buildings. These locations are similar to those at the base of a wall. However, the flashing must form around the toe of the angle. Also, if the angle spans any considerable distance, it will most likely be either welded or bolted back to the structure of the building. A flexible flashing can be formed around the bolt heads (see Figure 5).
Window and door heads
FLASHINGS AT WINDOW HEADS are very similar to those at shelf angles. There is usually a lintel or shelf angle that supports the masonry veneer above the window. However, the lintels are not continuous. It is therefore prudent to provide an upturned end dam at the end of the lintel. The intent of this practice is to prevent water from flowing off the end of the lintel, discharging water at the jamb of the window or door.
Window and door jambs
THESE LOCATIONS, along with other penetrations through the wall such as mechanical louvers, create conditions in which water can potentially flow out of the drainage cavity migrating down the side of the window, door, or both, creating a leak.