Window flashing order — sill pan, jambs, head, then WRB, lapped to shed water
Flash a window bottom-up so each layer laps the one below: (1) sill pan first, turned up the jambs, (2) set the window, (3) jamb flashing, (4) head flashing, (5) WRB lapped down over the head. Reverse the order and water gets behind the wall.
What this diagram shows
A wall elevation showing the correct order to flash a window so water sheds outward. First, sill-pan flashing goes in and is turned up the jambs. Second, the window is set with its nailing flange against the wall. Third, jamb flashing covers the side flanges. Fourth, head flashing covers the top flange. Fifth, the weather-resistive barrier laps down over the head flashing, shingle-fashion, so every layer overlaps the one below. Insert or pocket replacements skip the flashing and use sealant plus backer rod instead. Reverse the laps and water gets driven behind the wall.
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