How is wall flashing done on a metal roof?
Short answer. Metal roofs use sidewall flashing where the side of a panel runs along a wall, and endwall or headwall flashing where the top of a slope dies into a wall. Both are formed trims fastened to the roof panels and turned up the wall behind the housewrap and siding, or under counterflashing on masonry, with closures and sealant sealing the panel ribs and a kickout where the roof edge meets the wall.
Sidewall flashing
- Runs along the wall parallel to the panels, with one leg on the roof and one up the wall.
- The roof leg fastens to the panel rib or a cleat, depending on the system; on standing seam it often attaches to a Z closure.
- The wall leg turns up behind the housewrap and siding, or tucks under counterflashing on brick.
- At the bottom, a kickout diverts water into the gutter.
Endwall or headwall flashing
- Runs across the top of the panels where the slope meets a wall.
- Profiled foam closures, set in sealant, fill the ribs at the panel ends so wind-driven rain cannot blow up under the flashing.
- The flashing laps down over the closures and panel tops, fastens through them, and turns up the wall behind the housewrap and siding.
Laps with the wall
The housewrap or other water-resistive barrier must lap over the wall leg of the flashing, never behind it, and the siding should stop slightly above the roof surface so it does not wick water or rot along its bottom edge. On brick or stone, a separate counterflashing cut into a mortar joint laps down over the wall leg.
Common failures
- Flashing caulked to the face of the siding with no lap behind it.
- Missing closures at an endwall.
- Fasteners through the flashing in the water path.
- No kickout at the bottom of a sidewall.
- Siding sitting on the roof and wicking water.
When a leak appears on a wall below a metal roof, the wall flashing is the first suspect. See metal roofing in Georgia and roof flashing explained.