What flashing goes where a roof meets a wall?
Sidewall: the roof runs along the wall
Step flashing comes in L-shaped pieces, one for each course of shingles. Each piece sits on the shingle below and under the shingle above, so water that reaches the wall is passed down the roof one piece at a time. The wall leg goes up behind the housewrap and siding. The code minimum is 4 inches up and 4 inches out, and many shingle makers prefer 5 by 5.
Headwall: the roof ends at a wall
A single continuous apron runs across the top of the last shingle course and up the wall, with siding or counterflashing lapping over its vertical leg. It is nailed into the roof deck, not the wall, so the roof and wall can move independently.
The kickout
At the bottom of a sidewall, where the roof edge meets the wall, a kickout diverts the water coming down the step flashing out into the gutter instead of behind the siding. The residential code calls for it, and missing kickouts are a common cause of rotted sheathing below roof edges.
Siding and masonry
- Vinyl, fiber cement or wood siding: laps over the flashing and stops above the roof surface by the clearance its manufacturer requires, so it does not wick water.
- Brick and stone: counterflashing is cut into a mortar joint and laps over the step flashing.
- Stucco: must tie into the weather barrier behind it, which often takes both the roofer and the stucco contractor.
How these joints fail
- Flashing caulked to the face of the siding with nothing behind it.
- One long bent strip instead of individual steps.
- No kickout.
- Siding resting on the shingles.