Where a sloped roof ends against a vertical wall, water that runs down the roof has to go somewhere. Step flashing handles the courses of shingle that climb the wall, but at the lowest point of that wall, the last piece has to turn water out and away from the siding or brick. That piece is called a kick-out flashing, sometimes a diverter. Without one, water runs down the face of the wall behind the cladding, collects at the bottom, and shows up later as a stain on the interior wall or soft sheathing at the bottom plate.
St. Louis houses make this detail more common than people expect. Brick veneer, cedar lap, vinyl siding, and stucco all meet roof slopes in the same way, and the older cross-gabled and Tudor-style houses in the city and the county have more of these junctions than a simple ranch does. A gable that ends into a sidewall creates a corner where water sheds faster than it can drain. If the gutter sits right at that corner, the kick-out is the piece that keeps water out of the gap between the wall and the trough.
Material and spec
Kick-out flashing is usually bent from the same sheet metal as the rest of the flashing package, most often galvanized steel or aluminum. The spec should name the metal, the gauge, and the finish. A piece that is too thin dents under hail and flexes when the snow slides off, which opens the joint it was meant to close. A piece that is too thick does not bend cleanly on site and cracks at the fold. Ask for the metal and gauge in writing, not just the word "flashing" on a line item.
The length and angle matter as much as the metal. The diverter should project past the face of the siding or brick far enough to clear the gutter's front edge, and it should bend down at an angle steep enough that water drops into the trough instead of running along the flashing and spilling behind the wall. On a short run, a flat piece will hold water. On a long roof slope, one piece may not be enough, and the spec should show whether the crew uses one continuous piece or several overlapped sections.
The kick-out has to be integrated with the step flashing above it, not just set next to it. Each shingle course that climbs the wall should lap onto the step flashing, and the step flashing should lap onto the kick-out at the bottom. The lap direction matters: upper pieces go over lower pieces so that water always runs out of the assembly. If the drawings or the proposal show the kick-out as a separate line from the step flashing, ask how the two overlap, and ask whether the crew will set the kick-out before the first shingle course goes on.
Sealant is the other place a spec can go vague. Roofers sometimes seal the top edge of the diverter to the wall, and that is reasonable where the metal is held tight to the cladding. But sealant is not a substitute for a lap. A bead of caulk that fails after two winters leaves the joint depending on the metal alone. Ask which sealant the crew uses, what it is rated for at the temperatures a St. Louis January brings, and whether the sealed joint appears in the photo log.
Freeze and thaw cycles are the reason this detail gets tested every winter here. Meltwater from the roof reaches the cold metal at the lowest part of the junction and can refreeze there. A kick-out with the right angle moves that water into the gutter before it can freeze behind the wall. A kick-out that is too flat lets meltwater pool and refreeze, and the ice builds up until it pushes water uphill under the flashing. This is a spec detail that shows up on the first hard cold morning, not on the day of the install.
What it costs
A kick-out flashing is a small line on a roof quote, and it is often folded into a general flashing allowance rather than priced on its own. That is a fair way to handle a simple job, but it means you cannot see what the crew plans to install. Ask whether the price is per piece or per linear foot of the junction, and whether material and labor are both counted. On a roof with several wall junctions, the total can add up even though each piece is inexpensive.
The cost difference between a well-specified kick-out and a minimal one is usually small compared with the cost of repairing rotted sheathing or brick mortar behind the wall. The flashing is a modest amount of metal and a short stretch of crew time at each junction. A rotted bottom plate or a stained interior wall is a separate repair with its own trades and its own timeline. Price the kick-out as part of the water path, not as an extra.
Some quotes show the kick-out as an add-on or an option. Ask why it is an option. On a wall where the roof sheds directly toward the gutter, the crew should install one as a standard part of the flashing work, and an option line suggests the quote was not built around the actual wall. If the choice is genuinely optional on your house, ask the crew to show you where the water would go without it.
What to ask
- Which metal, what gauge, and what finish will the kick-out be made from, and will it match the rest of the flashing package?
- How far will the diverter project past the siding or brick, and at what bend angle?
- Is the kick-out one continuous piece or several sections, and how is each lap made?
- How does the kick-out overlap the step flashing above it, and which piece goes on first?
- Which sealant is used at the top edge, and is it rated for a St. Louis winter?
- Will the kick-out be set before the first shingle course goes on, and will the photo log show it in place?
- Where will the gutter sit relative to the diverter, and will the gutter be re-hung if it sits too close to the wall?
Ask for the scope in writing, with each junction listed by location rather than as a count of flashing pieces. A written scope that says "kick-out at the north gable wall, metal and gauge stated, lap to step flashing shown" gives you something to check against the finished roof. Keys Roofing documents the flashing at each junction with photos and measurements, and puts that written scope in your hands before the work starts. You keep that record, and it is the same record you would want if water ever shows up at that corner.
If you already see a leak or staining at a wall where the roof ends, check the kick-out before you assume the shingles are the problem. Water at a sidewall usually starts at the bottom of the junction, not at the top. To ask about a written scope or have your wall junctions walked, call Keys at (314) 220-2333 and request a look at the kick-out and the step flashing above it.