Kickout Flashing: The Missing Detail That Rots Walls
There is a small piece of metal at the bottom of every roof-to-wall junction that almost nobody knows the name of, and when it is missing, the damage it causes is usually blamed on something else entirely. It is called a kickout flashing, and it is one of the least expensive components on a roof and one of the most consequential.
What a kickout flashing does
Where a roof plane runs into a vertical wall, water travels down the joint between them. Step flashing carries that water down the wall, shingle by shingle. But at the very bottom of that run, the water has to leave the roof and get into the gutter. A kickout flashing is the angled piece that diverts it out and away at that final point.
Without one, the water reaches the end of the step flashing and simply keeps going, straight into the gap where the wall meets the roof edge. From there it goes behind the siding, the stucco or the brick veneer, and it does that every single time it rains.
Why the damage is almost always misdiagnosed
This is the part that matters. A missing kickout does not produce a dripping ceiling. It produces slow, concealed saturation of wall sheathing and framing in one specific spot, and by the time anything is visible from inside, the damage has usually been developing for years.
The symptoms get attributed to almost anything else first:
- Peeling paint or bubbling stucco on one wall, blamed on sun exposure or a bad paint job.
- A musty smell in a room that never quite goes away, blamed on humidity.
- Soft or spongy siding low down on a wall, blamed on ground moisture or splash-back.
- Interior drywall staining at the base of a wall, blamed on plumbing.
- Insects, particularly carpenter ants and termites, drawn to permanently damp framing.
Meanwhile the roof itself looks perfect, because it is. The roof is not leaking. The water never gets inside the roof assembly at all. It is being delivered, quite efficiently, into the wall.
How to check whether yours is there
This is something you can look at yourself from the ground, and it takes about a minute per junction:
- Find where a roof edge meets a vertical wall. Dormers, garage roofs meeting the house, porch roofs, and any point where a lower roof abuts a taller wall.
- Look at the very bottom of that junction, right where the roof edge ends.
- You are looking for a small angled metal tab, usually a few inches tall, turned outward toward the gutter. It will look almost like a tiny scoop or dam.
- If the step flashing just stops flush against the wall with nothing at the end, there is no kickout.
On stucco and synthetic stucco walls this matters more than anywhere else, because those systems hold moisture against the sheathing rather than letting it drain and dry. On brick veneer it matters nearly as much.
The other common failure: a kickout that is too short
A kickout can also be present and still inadequate. If it is undersized, or if it has been installed flat against the wall rather than angled out, it diverts some of the water and lets the rest past. Partial diversion over fifteen years still rots a wall, just more slowly.
Why it gets left off in the first place
Two reasons, and neither is good. The first is that it takes an extra few minutes and a fabricated piece of metal, and on a job being priced to the bone it is an easy thing to skip. The second is simply that some crews were never taught the detail, and a roof without one looks finished.
It is also worth knowing that the requirement has been in residential building codes for years. That does not mean every roof has one. It means that a roof without one was very likely not inspected properly.
What it costs to put right
If the wall behind it is still sound, retrofitting a kickout is a small job. The last course of step flashing is opened up, the kickout is fabricated and set in, and the siding or stucco is closed back around it. It is the kind of repair that is trivial compared to what it prevents.
If the wall is already wet, the work is no longer a roofing job. Sheathing has to come off, framing has to be assessed, and the wall has to be rebuilt from the outside in. That is the reason to look now rather than after the paint starts to bubble.
Our roofing repair team handles kickout retrofits as part of flashing work, and every free roof inspection we carry out checks the roof-to-wall junctions specifically. If you are having a roof replaced, this is a detail worth asking about by name before you sign anything — it tells you a great deal about the crew.
Kickout flashing questions
It is a small angled piece of metal at the very bottom of a roof-to-wall junction that diverts water off the roof and into the gutter instead of letting it run behind the siding. It is the last piece in a step flashing run, and it is the one most often left out.
Look at the bottom of any point where a roof edge meets a vertical wall, such as where a garage or porch roof meets the main house. You should see a small angled tab turned outward toward the gutter. If the flashing just ends flat against the wall, it is missing.
Concealed water damage to wall sheathing and framing in one localised area. Typical signs are peeling paint or bubbling stucco on one wall, a persistent musty smell, soft siding low on the wall, or drywall staining at floor level. The roof itself usually looks fine.
The detail has been in residential building codes for years. In practice a great many houses do not have one, which usually means the roof was not inspected closely. Requirements vary by jurisdiction, so your local building department is the authority on your specific address.
Yes. The bottom course of step flashing is opened, the kickout is formed and installed, and the wall covering is closed back around it. It is a contained repair as long as the wall behind it has not already been damaged.
Considerably more. Stucco and synthetic stucco hold moisture against the sheathing rather than draining and drying quickly, so water delivered behind them has nowhere to go. Brick veneer is nearly as vulnerable. Vinyl and fiber cement drain better but still rot the sheathing behind them.