Kickout Flashing Installation

Where a sloped roof runs into a sidewall — a porch roof, a garage, a lower wing meeting the main house — the roof is flashed with step flashing, one piece per shingle course, marching up the wall. At the bottom of that run the roof edge ends but the wall keeps going down toward grade.

That junction is a gutter. Everything the roof plane sheds toward the wall, plus everything running down the wall, is concentrated into one line and delivered to the bottom of it. The kickout is the bottom-most piece of the step flashing run, and instead of lying flat like the pieces above it, it turns outward and throws that accumulated water into the gutter.

It is not a trim piece. It is the termination of a drainage path, and without it the drainage path terminates inside the wall.

Without a diverter, the water arriving at the bottom of that junction has one place to go: behind the cladding. It runs down the back of the siding, soaks the barrier and the sheathing, and wets the bottom plate and stud ends.

Every rain does it again, and nothing dries, because the water sits in a cavity in a shaded corner of the building. Nothing shows for years. Then it all shows at once: soft sheathing over several feet of wall, rotted plate and studs, a damaged rim joist, mould behind the drywall, and often insect damage that followed the moisture in.

Three dimensions decide whether a kickout works. Get one wrong and the part is decorative.

That last row catches experienced crews. If the wall is getting 3/4-inch lap siding over 1/2-inch of exterior foam, the kickout needs an extra inch and a quarter of reach that was not obvious to a roofer looking at bare sheathing. Ask what the wall assembly will be before you cut the piece.

A kickout can be a manufactured one-piece part, a shop-formed and soldered piece, or a field-bent piece from an oversized step flashing blank. The first two are the same thing as far as the wall is concerned; the third depends entirely on how the corner is closed.

Folding one from a blank

Start with a blank considerably larger than a standard step flashing — you need material to consume in the fold. Bend it into an L, roof leg and wall leg. Cut down the fold line from the bottom edge two to three inches, bend the lower part of the wall leg outward to form the flare, and fold the surplus from the roof leg up and over that corner so the lap sheds outward, the way a shingle does. Rivet and seal, or solder in copper or terne. The geometry carries the water; the sealant is insurance.

This is where correctly-fabricated kickouts still fail. The metal can be perfect and the assembly still leaks if the housewrap is behind it instead of over it.

1. 1

   Wall barrier first, but left free at the bottom

   The water-resistive barrier goes on before the roof meets it. Leave the lower courses loose, or slit them horizontally, so flashing flanges can be worked underneath later.

2. 2

   Turn the roof underlayment up the wall

   Run the roof underlayment — self-adhered membrane here — several inches up the sidewall before any metal goes on. That is the backup plane for everything above.

3. 3

   Set the kickout on the first course

   It goes at the bottom of the run, on the starter and first shingle course, roof leg over the underlayment, outlet aimed into the trough. Fasten high on the wall leg only, where the metal above covers the fastener.

4. 4

   Lap the barrier OVER the vertical flange

   The step people get backwards. The housewrap comes down on top of the wall leg, so water running down its face lands on the metal and is carried out. Tape the wrap to the flange. Tucked behind it instead, the flashing is a funnel aimed into the wall.

5. 5

   Step flashings in shingle fashion above it

   Each piece sits on the shingle course below and behind the barrier above, one per course. Nothing is caulked to make this work; the laps do the work.

6. 6

   Siding last, and held off the roof

   Cladding stops an inch or two short of the roof surface so the bottom edge drains and debris does not bridge the gap. Siding caulked tight to the shingles traps water against the flashing.

The scheduling problem is worth naming. The roofer is gone before the siding crew arrives, and that crew’s work involves pulling wrap and fitting trim exactly where the kickout is. Kickouts get bent flat, trimmed short or removed during siding more often than the roofer installs them wrong. Photograph the detail; look again after the siding goes on.

A kickout that discharges into the wrong place has moved the problem, not solved it. Two errors account for nearly all of them.

• ●The gutter runs past the kickout to the wall. Its end cap is now inboard of the discharge, so the kickout throws water onto the top of the gutter, over its back, or straight down between gutter and wall. The gutter has to stop short of the wall — an inch or so — with the outlet over the open trough.
• ●The kickout overshoots the trough. Flared too aggressively or set too high, it launches water past the gutter’s outer lip onto the ground, eroding the bed and splashing the base of the wall you were protecting. Sight down the flare before you fasten it.

The correct picture is boring: the lip sits above the trough, inboard of the outer edge, gutter end behind it.

Most people searching for this are looking at a house that does not have one. It can be added without tearing the wall apart — but it is siding work, not roof work.

1. 1

   Open the siding at the bottom of the run

   Release the courses immediately above the junction — a zip tool on vinyl, a siding or slate ripper on lap siding — enough to expose the barrier and the first step flashing. These pieces are going back on, so work carefully.

2. 2

   Lift the first course and the bottom step flashing

   Break the seal on the first shingle course at the wall, pull the fasteners from the lowest step flashing and remove it. That is the piece the kickout replaces.

3. 3

   Slit the barrier and work the flange in

   Cut a horizontal slit in the housewrap above where the wall leg lands, slide the flange up behind the wrap above and over the wrap below, then tape the slit so everything drains outward. The roof leg goes under the shingle course above.

4. 4

   Reset and check the gutter

   Re-seal the shingle course, replace the siding, and confirm the discharge lands in the trough. While the wall is open, probe the sheathing with an awl. If it sinks, the repair just changed scope.