Lapping and sealing. At the base of the wall,
through-wall flashing must be uninterrupted. At the joints and
corners of a house, the flashing should be lapped at least 6
inches and sealed. This is easily done if you're using
self-adhesive rubberized asphalt flashing. Otherwise, consult
the flashing manufacturer for recommendations regarding the
proper mastic or lap cement (Figure 6).
6. If the flexible flashing is not one of the
self-adhering types, use mastic to seal any
Note that some flashings react with certain mastics,
drastically affecting the performance of the flashings.
Extend the flashing at least to the front face of the brick.
Although the BIA recommends that the flashing should extend 1/4
inch beyond the brick face and turn down to form a drip, some
of the flexible flashing materials can deteriorate when exposed
to the weather. One solution with self-adhesive flashing is to
install a metal drip in conjunction with the flexible
If the flashing is installed sloppily - short of the face of
the brick - then the collected water won't be delivered to the
exterior. Remember, the core holes are typically only 3/4 inch
back from the face. Even if care is taken to ensure that the
flashing projects no less than 1/2 inch from the face of the
wall, the flashing can scoot back when mortar and brick are
laid over it, allowing water to enter the cores of the brick
This flashing has been
installed incorrectly, since it does not extend all the way to
the front face of the brick. Any water is directed into the
core holes of the brick instead of to the exterior.
Because of these problems, many installers extend the
flashing well past the face of the brick until the wall is
complete, then cut the flashing flush with the face of the
masonry. According to the BIA, this practice is acceptable,
although it is not recommended.