What is step flashing? The stair-step metal along a wall
Step flashing is the row of small metal pieces that keeps water out where a sloped roof runs into a wall. One missing piece can leak for years.
Step flashing is a series of small, L-shaped metal pieces installed one per shingle course where a sloped roof meets a vertical wall. Each piece laps over the one below it, like stair steps. Water that runs down the wall is passed from piece to piece and ends up on top of the shingles, not behind them.
Why it is many small pieces, not one long strip
A single long strip cannot handle a roof that moves. Shingles expand, the wall settles and the seasons flex everything a little. Small overlapping pieces slide against each other and keep the joint closed. A long strip tends to buckle, split or pull away.
Where you find it
Look at any spot where the roof slope ends against a wall that rises above it. That can be a dormer side, a second-story wall over a porch roof or the side of a chimney. At a chimney, step flashing is the lower layer, and a separate cover called counter flashing goes over its top edge. We cover that setup in step flashing around a chimney.
How step flashing fails
The metal itself rarely wears out first. The trouble is usually in how it was fitted or what happened to the wall above it.
- A run of flashing that is one long bent strip instead of separate pieces.
- Pieces that were nailed to the wall as well as the roof, so they cannot move.
- Rust, especially on bare steel, which weakens the lower edge.
- Siding or trim that was pushed down over the top and now traps water.
- Tar or sealant smeared along the line in place of a proper overlap.
Tar is the warning sign. It usually means someone chased a leak here before and covered the symptom.
What a leak from it looks like
The stain tends to sit along the ceiling or wall that backs onto the roof junction. It often grows after heavy rain that blows toward the wall. It can look like a bad shingle, but the shingles may be fine. Water is slipping behind a piece that no longer laps correctly.
What to check from the ground
Stand in the yard and use binoculars. Follow the line where the roof meets the wall. You are looking for gaps, rust streaks, lifted metal and dark smears of tar. Take photos from a few angles.
Inside, look at the ceiling and wall along that same line. If you have attic access, use a flashlight from the joists and check the framing below the junction for dark staining. Do not step between the joists.
Why we do not show the repair
Fixing step flashing means lifting shingles along the roof edge and working beside a wall. That is work at height, and one slip can end badly. We leave it out on purpose. Photograph the line, note which room is stained and ask a roofer to show you the pieces they plan to replace. A good one will point to each course, not wave at the whole wall.
Frequently asked questions
What is step flashing?
It is a row of small bent metal pieces, one per shingle course, installed where a sloped roof meets a wall. Each piece laps over the one below it so water is guided onto the shingles.
Why is step flashing made of separate pieces?
Separate pieces slide against each other as the roof and wall move. One long strip tends to buckle or tear.
Can sealant replace step flashing?
No. Sealant dries and splits within a few seasons. A bead of tar along the wall usually means the metal was already failing.
What does a step flashing leak look like?
A ceiling or wall stain along the roof and wall junction, often after wind-driven rain, while the shingles nearby look fine.
How do I check step flashing safely?
Use binoculars from the yard to follow the junction, and look at the ceiling and attic framing from inside. Do not go on the roof.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NRCA. National Roofing Contractors Association
- US OSHA. 1926.501 — Duty to have fall protection (OSHA)