FLASHING... Tying the loose ends

Below Wall Openings & On Shelf Angles

Installation Below Wall Openings

The installation of the flashing for a sill condition is similar in both cavity and veneer wall systems. See Figure 6 & 7. An end dam is used once again to act as a moisture deterrent. The flashing collects any entrant water, and the end dam ensures that the water will be directed to the exterior.Weep holes are installed to provide an avenue of egress for the moisture. Ideally the end dam would be placed 6" to 8" beyond jamb lines above all wall openings.

On Shelf Angles

Shelf angles create a continuous horizontal break within the cavity, obstructing the vertical flow of moisture through the air space. If special attention is not given to the detailing and installation of shelf angles, moisture infiltration, efflorescence and brick spalling can occur. See Figure 8a. Due to the above factors, specifying the minimum amount of shelf angles will reduce the possibility of moisture damage.

 If possible, an alternative method of design is to eliminate all shelf angles at all floor lines and bear the exterior wythe of masonry on the foundation as shown in Figure 8b. This eliminates potential problems inherent in shelf angle design. This wythe of masonry can support its own weight for several stories, while wall ties provide lateral stability.

Another strategy is to bear the exterior wythe directly on the floor slab. See Figure 9. However, thermal bridging makes this type of system less energy efficient, and more reinforcement may be required in the slab to support the wall. Also, exposed slabs are susceptible to moisture infiltration, so special details must be developed to prevent wind driven rain from penetrating beneath the flashing and into the building. Flashing must be set in a continuous bed of mastic, or a self adhering flashing must be used to prevent the wind driven rain from entering beneath the flashing.

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