Know Your Roof · Flashing & Roof Edge
Step Flashing: How It Works
Quick answer
Step flashing is a series of small L-shaped metal pieces installed in a stair-step pattern where a sloped roof meets a vertical wall, like a dormer or the side of a chimney. Each piece overlaps the shingle course below it, so water is led down and out over the shingles instead of into the joint.
Last updated
How it goes in
- A piece of flashing goes over each course of shingles.
- One leg lies flat on the roof. The other turns up against the wall.
- The siding overlaps the upturned leg.
- Each piece laps the one below it, like shingles do.
Water has to run down the wall, onto the flashing, and out over the shingle surface.
Why it fails
Siding nailed through the flashing, which makes a leak path. A missing kickout at the bottom of the wall, so water runs behind the siding. Rust. Old pieces reused during a re-roof. Sealant standing in for proper overlap.
What a kickout is
Kickout flashing (also called a diverter) is a small angled piece at the bottom of the wall-to-roof joint. It kicks water out into the gutter. Without one, water can pour down behind the siding and rot the wall.
What does step flashing repair cost?
Step flashing along a wall or dormer is usually repaired in sections. Flashing repair around a wall, chimney, or valley typically runs $400 to $900. A minor repair that includes flashing, a vent boot, or one or two shingles runs $400 to $750. The final number depends on how much flashing is damaged and how hard it is to reach, and every job starts with a free roof inspection.
Looking for another word? See the roofing terms glossary, A to Z.