Head flashing (window or door)
Head flashing is the formed metal or tape flashing above a window or door that sheds water out and over the cladding, not behind it. Most-missed install-defect cause.
Ask Chalkline about this →A head flashing is the flashing fixed at the head (top) of a window or door opening that catches water tracking down the wall above, sheds it sideways past the window frame, and discharges it out over the cladding below. Together with the sill flashing underneath and the jamb flashings at the sides, the head flashing makes the four-sided water-shedding wrapper that keeps a window install dry over its service life.
Why it’s the most-missed install detail. The window install order ends with the cladding being fitted around and above the window. If the head flashing is not installed before the cladding goes up, retrofitting it is invasive: cladding sheets have to be lifted, the wall wrap repaired, the flashing inserted, then cladding refitted. Builders under time pressure skip it and rely on sealant; the sealant fails at 5 to 10 years and the wall above the window starts taking water.
Two common forms:
- Formed metal head flashing. Colorbond, aluminium, or copper bent to a top-fixed-flange-plus-vertical-drip profile. Fixed to the wall above the window, lapped over the wall wrap, and projecting out over the cladding by at least 10 to 15 mm to throw water clear.
- Self-adhesive flexible flashing tape. Modified bitumen or butyl. Often used as a backing layer behind a metal flashing on critical applications, or as the primary on lightweight cladding when the cladding’s own drip profile carries the water clear of the wall.
Install sequence (lightweight cladding, drained cavity):
- Wall wrap installed up over the rough opening.
- Sill flashing fitted first (see sill flashing).
- Window seated; jambs sealed.
- Head flashing fitted next, lapping onto the wall wrap above the window head. The wall wrap above is folded down over the head flashing’s vertical flange so the wrap-and-flashing-and-wrap stack drains outward.
- Cavity battens fitted, cladding installed, cladding line stopping above the head flashing’s drip so it stays exposed to discharge.
Masonry veneer: the head flashing is concealed in the brick cavity, sloping outward to weep holes in the brick course immediately above the window head.
Common defects (in the order they appear on residential inspections):
- Head flashing omitted, builder relied on sealant alone. Sealant cracks; water in the wall above.
- Lap direction wrong: wall wrap tucked over the head flashing instead of under. Water flows behind the flashing.
- Head flashing not projecting past the cladding plane. Water dribbles back under.
- Galvanised or zincalume head flashing in direct contact with treated timber. Galvanic corrosion in 5 years.
- Penetration sealing missed at flashing fixings, wind-driven rain reaches behind.
Also known as: window head flashing; weather flashing (loose); cap flashing (loose, confusing with cap flashings on parapets).
Category: Building science.
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Last updated: 2026-05-16. Verified: 2026-05-16. Quarterly review for currency.