What Is Kickout Flashing?

Kickout flashing is a small piece of angled metal that sits where a roof edge meets a wall, and its job is simple: kick the runoff away from the siding and into the gutter. When it is missing, you get one of the most notorious hidden leaks in home construction, because water runs down inside the wall instead of into the trough, and nobody sees it until the damage is done.

What kickout flashing is and where it goes

To picture it, imagine a sloped roof that runs down and dead-ends into a vertical wall, the kind of junction you see on a dormer, a second-story wall meeting a lower roof, or a garage roof tying into the house. Along that junction, small pieces of step flashing weave between the shingles and the wall to keep water out.

At the very bottom of that line, right where the roof edge and the gutter begin, the water that has been traveling down the roof-wall corner needs somewhere to go. Kickout flashing is the piece that catches it there and diverts it outward, away from the wall, so it drops cleanly into the gutter. Without that last kick, all that concentrated water pours straight down against the wall. For the broader story of how water travels off a roof and where it concentrates, see how roof runoff works.

It is part of the flashing family

Kickout flashing works with the other roof-edge parts, not in isolation. It ties into the step flashing above it and sits just over the gutter below it. Understanding the whole eave assembly helps; the overview of drip edge, fascia and soffit explained covers the parts that hand water off to the gutter at the roof edge.

Why missing kickout flashing causes hidden leaks

Here is what makes the missing-kickout problem so insidious. A roof-wall junction funnels water. All the rain that falls on that slope of roof gets channeled toward the corner where it meets the wall, and it arrives at the bottom of that line in a concentrated stream. If there is no kickout to redirect it, that stream hits the wall and finds its way behind the siding.

Once water is behind the siding, it soaks the sheathing and can reach the wall framing. Because the leak is inside the wall cavity, there is no dripping ceiling and no obvious puddle. The wood stays wet, and over months or years it rots. Homeowners often discover the problem only when the damage is extensive, sometimes when siding is removed for an unrelated project.

Signs to look for

You can often spot the symptoms from the ground, even if the flashing itself is hard to see.

Sign	Where to look	What it may mean
Staining or streaks on siding	Below a roof-to-wall junction	Runoff hitting the wall instead of the gutter
Peeling paint or swollen siding	The wall just under the roof edge	Repeated wetting of the wall surface
Musty smell or damp spot inside	Interior wall near that corner	Water reaching the wall cavity
Soft or discolored sheathing	Behind the siding, if exposed	Longer-term rot from a hidden leak
Erosion or splash marks below	Ground or lower roof at the corner	Concentrated water dumping in one spot

The clue is concentration

The tell with kickout problems is that everything concentrates at one corner. A roof-wall junction gathers water and delivers it to a single point. If you notice staining, splashing, or erosion focused right where a roof meets a wall, missing or failed kickout flashing is a leading suspect.

Adding it is roofer work

Kickout flashing is small and cheap, but installing it correctly is not a casual afternoon job. It has to integrate with the step flashing, lap correctly with the siding, and terminate cleanly above the gutter, all at the roof edge and usually a story or more off the ground. A piece that is installed but poorly integrated can trap water and create a new leak path instead of solving the old one.

Common mistakes

• Assuming a stained wall is just cosmetic. Streaking below a roof-wall corner can signal water going where you cannot see it. Do not paint over it without checking the cause.
• Relying on caulk instead of flashing. Sealant at a roof-wall junction is a stopgap, not a substitute for a proper kickout that physically redirects the water.
• Bending the last step flashing outward as a fix. A real kickout is a purpose-made piece integrated with the surrounding flashing, not an improvised bend that can trap debris and water.
• Ignoring the gutter position. The flashing needs to deliver water into the trough. If the gutter does not extend under that corner, the kickout has nowhere to send the water.
• Treating it as a DIY. The part is simple, but its integration with roofing and siding at height is not. This is usually a job for a roofer.

The bottom line

Kickout flashing is a tiny part with an outsized job: it keeps concentrated roof runoff from pouring down inside your wall at a roof-to-wall junction. Missing it is a classic source of hidden rot, because the leak hides in the wall cavity for years. If you see staining, splashing, or dampness focused at a corner where a roof meets a wall, kickout flashing is worth investigating, and re-integrating it is a job for a roofing professional.