The spot where a roof slope runs up against a vertical wall is one of the least forgiving details on a house, and step flashing is what keeps it dry. Done right, you never think about it. Done wrong, the damage shows up in the wall framing long before it reaches your ceiling.
We see this most on two-story homes where a garage or porch roof ties into the main wall, and on dormers. The shingles look perfect. The siding looks fine. Meanwhile the sheathing behind it has been wet for years.
How Step Flashing Is Supposed to Work
Step flashing is not one piece of metal. It is a stack of small L-shaped pieces, each bent to turn up the wall and out onto the roof, and each one woven into a single shingle course. Every piece laps over the piece below it, like shingles do, so water stepping down the wall is always handed off to the next piece.
Two rules make or break it:
- Each piece belongs in its own course. One long strip of metal cannot do this job on a sloped run. Water finds the horizontal seam where the strip meets the shingles.
- The metal is fastened to the roof, not the wall. Nailing through both surfaces locks the flashing in place while the house moves seasonally, and the metal tears or the fasteners back out.
Above the step flashing, the wall covering or a counterflashing laps down over the vertical legs, so nothing is exposed to the weather.
Continuous Flashing Has Its Place — Just Not Here
Continuous flashing, also called apron flashing, is the correct choice where a roof slope ends against a wall horizontally, such as beneath a second-story wall at the top of a lower roof. There the water runs across the metal, not down its length, and one piece works.
Confusing the two is a common error on quick repairs. If you can see a single long piece of metal running up the sloped side of a wall junction, that detail is on borrowed time.
The Missing Kick-Out: Where Hidden Wall Rot Starts
At the bottom of every sloped step flashing run, one more piece is required: a kick-out. It is a small flared or soldered piece that turns the accumulated water away from the wall and out into the gutter.
Leave it off — and it is left off constantly, on new construction as much as anywhere — and the entire drainage of that roof slope pours down behind the siding at the corner. There is no drip, no stain, no warning. The wall sheathing rots, the bottom plate goes soft, and the first anyone knows is when a trim board falls apart or an interior wall stains near the floor.
If you have a roof slope ending against a wall above a gutter, walk out and look at that corner. A missing kick-out is one of the few serious roofing defects a homeowner can spot from the ground.
How Siding and Masonry Change the Repair
The wall material decides the method.
Lap siding. A roofer can usually pry a course loose, slide new step flashing behind it, and re-secure the siding without a siding contractor.
Brick or stone. The vertical legs must be covered by a counterflashing let into a mortar joint. Sealing flashing to the face of brick with caulk fails within a few Texas summers of thermal cycling.
Stucco. The hardest case. Correct work means cutting the stucco back to expose the flashing, and it needs a patching plan before anyone starts.
Siding installed too low. Siding that touches the shingles wicks water and traps debris; it needs a clearance gap above the roof surface. Related trim and ventilation details matter here too — see our notes on soffit and roof repair.
Signs You Have a Wall-to-Roof Flashing Leak
- Stains on an interior wall rather than a ceiling, sometimes low on the wall.
- Peeling paint, bubbled siding, or soft trim at the bottom corner of a roof-to-wall junction.
- Damp or discolored sheathing visible from inside a garage where the roof ties in.
Because the water travels inside the wall cavity, the entry point is almost always higher than the damage. Diagnosing it takes someone willing to look at the whole assembly rather than the nearest stain — the same approach behind good roof flashing repair generally.
Reflashing Is Part of a Proper Reroof
Step flashing is not meant to be reused. Old pieces are bent, fastened, and often corroded at the bottom of the run where water sits longest. A quality roof replacement includes new step flashing woven into the new courses, a new kick-out at every run, and counterflashing addressed on masonry walls.
If your leak is isolated and the roof is otherwise sound, a targeted roof repair can rebuild just that junction so it sheds water the way it should have from day one.
Frequently Asked Questions
What is step flashing and why does it fail? Step flashing is a series of small bent metal pieces, one woven into each shingle course, where a roof slope runs alongside a wall. It fails when it is replaced with a single long strip, when it is nailed to both surfaces, or when it corrodes with age.
What does a kick-out flashing do? A kick-out is the small angled piece at the bottom of a step flashing run that throws water away from the wall and into the gutter. Without one, every storm sends water straight down inside the siding, which is a leading cause of hidden wall rot.
Can step flashing be replaced without removing siding? Sometimes. On lap siding a roofer can often work a course loose and slide new flashing behind it. Brick and stucco walls usually need a counterflashing cut into a mortar joint instead. The right method depends on the wall, not the roof.
Suspect a leak where your roof meets a wall? Call Cannon Roofing at (940) 627-1045 or request a free quote. We have been rebuilding these junctions across Decatur, Wise County & Greater North Texas since 1994.