A kickout is a small piece of flashing at the bottom of a roof-to-wall intersection — and its absence is behind an outsized share of concealed wall rot on otherwise sound buildings.
Where a sloped roof edge meets a vertical wall, all the water running down that roof edge reaches the bottom of the intersection and has to go somewhere. A kickout flashing — a small diverter at that low point — is what turns the water out and into the gutter instead of letting it run behind the wall cladding. It is one of the smallest details on a building and one of the most consequential when it is missing.
The failures are predictable and repeat constantly. The sections below cover the four that ACE sees most — the missing kickout, roof-to-wall water diversion, hidden wall rot, and gutter and downspout coordination — and how to detail the intersection so the water goes where it should.
These challenges rarely stay in one silo: the same discipline runs through our field notes on through-wall flashing failures, the same playbook behind counterflashing and reglet failures, and lessons from insulating glass unit seal failures, and it all ladders up to ACE’s broader remedial waterproofing and repair.
The missing kickout is the defining failure, because the intersection often looks finished without one, so it is left off entirely and no one notices until water damage appears inside or behind the cladding. A properly sized kickout installed at the low end of every roof-to-wall intersection is the fix, and it must be present from the start.
Because the piece is small and easy to omit, it is one of the most frequently missed details in the field, and its absence is disproportionately represented in wall-rot claims.
Specifying the kickout explicitly and inspecting for it during construction is a tiny step that prevents a large and expensive category of concealed damage.
Representative of the roof-to-wall failure patterns ACE finds in investigation and peer-review work. Illustrative distribution, not a published statistic.
Roof-to-wall water diversion is what the kickout accomplishes, because the concentrated flow coming off the roof edge must be turned decisively away from the wall and into the gutter rather than allowed to sheet down the wall face and behind the cladding. A kickout with enough size and angle to divert the real flow is what does the job.
An undersized or shallow kickout diverts some water but lets the rest run behind the cladding, so the diversion has to be sized for the actual roof area draining to that point.
The step-flashing above the kickout has to integrate with it continuously, so the water is guided all the way down and out rather than finding a gap at the transition.
A roof-to-wall intersection without a proper kickout runs concentrated roof water behind the cladding and rots the wall base out of sight.
Install a correctly sized kickout, integrate the step flashing, and coordinate the gutter and downspout to carry the diverted water.
The water is diverted outward into the gutter, the wall base stays dry, and the concealed rot never starts.
Hidden wall rot is the damage a missing or failed kickout produces, because the diverted-behind-the-cladding water saturates the sheathing and framing at the base of the wall, where it decays out of sight for years before the symptoms surface. By the time staining or soft sheathing appears, the repair is structural rather than cosmetic.
The concealed nature is what makes this failure so costly, since the water enters at one small point but spreads through the wall base, and the diagnosis often requires opening the wall.
Preventing the rot is entirely about keeping the water out at the intersection, which is why the small kickout detail carries such large downstream consequences.
Get the roof-to-wall intersection reviewed for a proper kickout and gutter coordination before damage hides.
Schedule a consultationCall (866) 389-8883Gutter and downspout coordination determines whether the kickout actually helps, because the kickout has to deliver its diverted water into a gutter that can carry it away, and a kickout that dumps water past the end of the gutter simply moves the problem. The gutter has to begin where the kickout discharges.
Where the gutter stops short of the intersection, or the downspout cannot handle the flow, the diverted water overflows back toward the wall, so the drainage capacity has to match the diverted flow.
The most valuable move overall is treating the roof-to-wall intersection as a coordinated system — kickout, step flashing, gutter, and downspout together — and verifying it in the field, because the whole assembly fails if any piece is missing.
In ACE’s field work, most kickout flashing failures problems trace back to a few recurring locations — Kickout omitted entirely, Undersized / poor diversion, and Concealed wall rot at base — rather than the open field of the wall or roof. The cost of resolving them climbs by roughly an order of magnitude at each stage: a detail corrected during design costs a fraction of the same fix during construction, which is itself far cheaper than a repair once the facility is operating. That economics is why we push envelope decisions as early in the project as possible.
Specify a sized kickout, integrated step flashing, and a gutter and downspout that begin where the kickout discharges.
Confirm a correctly sized kickout is installed and integrated at every roof-to-wall low point before cladding covers it.
Where a kickout is missing, inspect the wall base for concealed moisture and rot and correct the diversion.
Fill out the form below and we'll get back to you within 24 hours.
We've received your request and will be in touch within 24 hours.
