Finish TradesQuestion 253 of 700
When installing a window in an exterior wall with a weather-resistive barrier, the flashing should be lapped so that:
a.The head flashing tucks behind the sill pan
b.All flashing is installed after the siding
c.Upper pieces lap over lower pieces (shingle fashion) so water drains outward
d.Only caulk is used, with no flashing
Explanation
Flashing must be shingle-lapped, with the sill pan first, jamb flashing over the sill, and head flashing lapping over the jambs and tucked under the upper WRB, so water always sheds down and out. Reversing the laps, flashing after siding, or relying on caulk alone traps water and causes leaks.
Law Reference: 2025 CA Residential Code §R703Practice all 700 questions free — no signup required.
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