What exactly is a kickout flashing and where does it go?

A kickout flashing (diverter flashing) is a small, L-shaped metal piece that directs water away from the wall-cladding intersection where a roof slope meets a vertical sidewall. It sits at the lowest end of the step flashing run, right where the roof edge hits the wall.

Where it goes:

1. Location: Bottom termination of step flashing (eave side of the roof-to-wall intersection).
2. Orientation: The vertical leg tucks behind the house wrap/WRB and siding. The horizontal leg kicks out and down over the roof shingles/underlayment, extending past the fascia/drip edge.
3. Goal: Force water exiting the step flashing onto the roof surface and into the gutter, not down the wall behind the siding.

Code & Standards:

• IRC R903.2.1 / IBC 1503.2: Require flashing at wall/roof intersections.
• IRC R703.4: Requires flashing to prevent water entry into the wall envelope.
• ARMA/NRCA/Manufacturer specs: Explicitly require kickouts at all roof-to-wall transitions.

Common Failures (Why you got dinged):

• Missing entirely: Water pours behind siding → rot, mold, stucco failure.
• Too short: Doesn't clear the fascia/cladding; water tracks back to wall.
• Wrong layering: Metal sits on top of house wrap/siding instead of behind it.
• Caulked instead of flashed: Sealant fails; not a code-approved flashing method.

Fix: Install a pre-formed or site-bent metal kickout (min. 4"x4" legs, 26ga galvanized/aluminum/copper). Integrate with step flashing: last step flashing piece overlaps kickout vertical leg; house wrap laps over kickout vertical leg; siding covers house wrap. Kickout horizontal leg sits on roof deck/underlayment, under shingles.

Bottom line: It’s a $5 part that prevents $50k wall rot. Install it correctly at every roof-to-wall bottom edge.

A kickout flashing (also called a diverter flashing) is a critical detail at the intersection of a roof and a vertical wall — specifically where a sloped roof meets a sidewall (like a dormer, chimney, or gable end). Its purpose is to divert water runoff from the roof away from the wall and into the gutter system, preventing water from running down the wall behind the siding, which can cause rot, mold, or structural damage.

Where It Goes:

• Location: At the low end of a roof-to-wall intersection, where the roof slope directs water toward the wall (not the gutter).
• Installation: It’s a bent metal (usually aluminum, galvanized steel, or copper) piece that:
• Extends under the roofing material (shingles, etc.) on the roof side.
• Flashes up the vertical wall at least 4–6 inches (per IRC R903.2.1 and manufacturer specs).
• Bends outward (the “kickout”) to direct water into the gutter, not behind the siding or down the wall face.
• Must overlap the wall’s water-resistive barrier (WRB) (like housewrap) and be integrated with step flashing and counterflashing.

Why the Inspector Dinged You:

Missing kickout flashing is a common and serious defect. Water intrusion here is slow but destructive — often hidden until rot is advanced. IRC R903.2.1 requires flashing at all roof-to-wall intersections to prevent water penetration. Many manufacturers (e.g., GAF, Owens Corning) mandate kickouts in their installation guides for warranty compliance.

Fix It:

• Remove the last few shingles near the wall.
• Install a proper kickout flashing (prefabricated or field-bent from 0.019” aluminum).
• Ensure it laps under roofing, up the wall, and into the gutter.
• Seal with compatible roofing cement if needed, but mechanical integration is key — don’t rely on sealant alone.

Bottom line: This isn’t optional. It’s a code-required, moisture-management detail. If you’re not comfortable installing it correctly, hire a licensed roofer — improper installation can worsen the problem. (IRC 2021: R903.2.1, R703.8)