Kick-Out Flashing: The Small Part That Stops Wall Rot

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Kick-out flashing is one of the cheapest parts on a house and one of the most consequential when it is missing. It sits at the bottom of a roof-to-wall junction, where a lower roof ends against a taller wall, and its only job is to throw water away from the wall and into the gutter. Without it, the runoff that has been traveling down the step flashing can pour straight behind the siding or stucco at exactly the point where the wall continues below the roof. The damage that follows is usually hidden inside the wall for years. This guide explains what kick out flashing is, where it is needed, what hidden rot and mold can look like below a missing diverter, how it relates to stucco, siding, house wrap and gutters, how inspectors evaluate it and what retrofits typically cost. It summarizes EPA mold guidance and general building practice; for active water damage or mold, consult a qualified contractor.

Part of our Structure & Exterior guide — start there for the full picture →

What Kick-Out Flashing Is

A kick-out flashing, also called a diverter flashing or kickout, is a small, specially shaped piece of metal or molded plastic installed at the lowest step flashing where a roof edge terminates against a wall that continues downward. It has a flat leg that sits under the shingle and against the wall like a normal step flashing, plus a flared or angled lip that projects out from the wall. That lip turns water away from the wall surface and directs it into the gutter or off the roof edge.

The detail exists because of how step flashing works. Each piece of step flashing along a roof-to-wall joint passes water down the roof, and by the time it reaches the eave, a significant amount of runoff is concentrated against the wall. If the wall ended at that point, the water would simply drop to the ground. But where the wall continues below the roof, as it does when a garage roof meets a two-story wall or a porch roof runs into the side of a house, the water has nowhere to go but down the face of the wall and, often, behind it.

Typical locations

• Where a garage or one-story roof meets the side of a taller house.
• Where a porch or bay roof ends partway along an exterior wall.
• At dormers whose cheek walls extend below the roof edge.
• At roof-to-chimney junctions where a chimney chase continues below the eave.
• Where a second-story wall rises out of a lower roof that terminates at a gutter.

Builders and the shingle industry have recognized this detail for many years, and current residential codes in many jurisdictions call for a diverter at these locations, though adoption and enforcement vary. Many older homes, and some newer ones, were built without them.

Hidden Rot and Mold in Walls Below

The damage from a missing kick-out tends to follow a recognizable pattern. Water flows off the end of the step flashing and onto the wall in a narrow band just below the roof edge. Some runs down the face of the cladding. Some gets behind it through the joint between the gutter end, fascia and wall, and from there into the weather barrier, sheathing and framing below. Because the wetting repeats with every rain and snowmelt, materials inside the wall rarely dry fully.

Common outward signs include:

• A vertical or diagonal stain on siding or stucco below the roof edge.
• Peeling paint, swollen trim or soft siding in that zone.
• Cracked, bulging or crumbling stucco just under the roof-wall corner.
• Interior stains on drywall or baseboard on the other side of that wall.
• Rotting window frames or sills directly below the roof-wall intersection.
• Musty odors in the room behind the wall.

When contractors open these walls, they often find damage well beyond what was visible: rotted sheathing, decayed studs and bottom plates, rusted fasteners and wet insulation. In stucco homes, the damage may extend a few feet below and to the side of the corner before any surface cracking appears.

What EPA says about moisture and mold

The EPA’s guidance is direct: the key to mold control is moisture control, and when leaks occur, drying wet materials within 24 to 48 hours will in most cases prevent mold growth. The agency also lists areas inside walls among the places hidden mold can occur. A wall cavity that is rewetted every storm cannot dry on that timeline, so a missing kick-out can create persistent hidden moisture. The EPA advises fixing the water problem when cleaning up mold, and its mold cleanup guidance suggests that areas of mold growth larger than about 10 square feet, or situations with significant water damage, call for more extensive cleanup guidance and often a professional. Anyone with health concerns related to mold should talk with a physician.

Stucco, Siding and the Weather Barrier

How badly a missing kick-out affects a wall depends partly on the cladding and the weather barrier behind it.

Stucco and manufactured stone

Traditional three-coat stucco and adhered manufactured stone are reservoir claddings: they absorb water and can hold it against the wall behind. When roof runoff is concentrated against them at a roof-wall corner, the weather-resistive barrier behind is put under heavy, repeated load. Stucco homes with missing kick-outs are a well-known source of hidden wall rot, and the visible symptoms often look minor compared to what is behind them. Our stucco repair guide explains why surface patching without fixing the water path tends to fail.

Retrofitting kick-out flashing on stucco usually means cutting away a section of stucco at the corner, installing the diverter properly integrated with the step flashing and weather barrier, and patching the stucco. It is not a quick fix, but it is far less costly than opening a large section of wall later.

Lap siding, fiber cement and vinyl

Wood, fiber cement and vinyl siding generally allow some drainage and drying behind them, which can slow the damage, but they do not prevent it. Water directed into the corner can still saturate trim, rot wood siding and sheathing, and leak around windows below. Replacing siding in that area is often part of a kick-out retrofit. Our siding repair guide covers the related repairs.

House wrap and integration

Behind the cladding, the weather-resistive barrier is the second line of defense. A kick-out only works well when it is lapped correctly with that barrier: the barrier above should lap over the flashing’s wall leg, and the flashing should lap over the barrier below. Reverse laps funnel water behind the wrap. Our guide to house wrap and weather barriers explains shingle-style lapping and why it matters at every penetration and transition.

Gutters, Downspouts and the Kick-Out

A kick-out works with the gutter, not instead of it. The diverter throws water into the end of the gutter, and the gutter carries it to a downspout. Several gutter issues commonly show up alongside kick-out problems:

• Gutter end caps tight against the wall. When the gutter runs right up to the wall, it can block the space a kick-out needs. Installers sometimes trim the gutter end back slightly or use a kick-out designed to fit.
• Overflowing gutters at the corner. Roof-wall corners collect a lot of water. If the gutter overflows there, the kick-out cannot prevent splashing onto the wall.
• Leaking end caps or seams. A gutter leaking at the end cap can wet the same corner the kick-out is meant to protect.
• Downspouts emptying near the foundation. Water diverted into the gutter still needs to be carried away from the house.

The EPA lists cleaning and repairing roof gutters regularly among its moisture and mold prevention tips. Our guides on gutter repair and downspout extensions cover the rest of the drainage path.

Snow and ice

Along the Front Range, roof-wall corners often collect drifted snow and ice. Meltwater running down against a wall during sunny winter days can reach the same vulnerable spot, sometimes when gutters are frozen. A properly installed kick-out still helps, but ice dams at the eave can back water up behind flashing, so attic insulation, ventilation and gutter condition all play a part.

Types of Kick-Outs and Common Installation Mistakes

Kick-out flashings come in a few common forms. Prefabricated molded plastic diverters are widely sold and are shaped as a single seamless piece, which avoids the leaky corner seam of some field-bent versions. Prefabricated metal kick-outs, typically aluminum, galvanized steel or copper, are also common and can be painted or matched to existing trim. Some roofers bend their own from sheet metal; a well-made one is soldered or sealed at the fold so the diverter does not leak at its own corner.

Whatever the material, the diverter has to be large enough to direct water past the gutter end and into the trough, and it has to be placed at the very bottom of the step flashing run, not one or two courses up. Several installation mistakes come up regularly:

• Diverter installed over the siding. A kick-out nailed and caulked to the face of the cladding can still leave the weather barrier behind it unprotected.
• Too small or too short. A lip that barely projects from the wall may send water into the joint between gutter and fascia instead of into the gutter.
• Reverse-lapped weather barrier. If the house wrap below is tucked over the flashing rather than under it, water is channeled behind the wrap.
• Field-bent flashing with an open corner. A simple bent piece that is not sealed at the fold can leak through its own seam.
• Sealant used in place of a diverter. A blob of caulk at the corner may slow water briefly but does not redirect it.

Because the visible lip looks similar whether or not the hidden integration is right, a kick-out that is present but poorly installed can still allow damage. Staining or cracking below an existing kick-out is a sign the detail may need to be checked more closely.

How Inspectors Evaluate Kick-Out Flashing

The ASHI Standard of Practice includes flashing in both the roofing and exterior sections, listing roof flashing and roof drainage systems along with wall coverings, flashing and trim among the items an inspector shall inspect. Kick-outs sit at the intersection of those categories, and many inspectors specifically look for them at every roof-wall termination.

A typical evaluation includes:

• Identifying each place a roof edge ends against a continuing wall.
• Checking from the ground, a ladder or a camera whether a diverter is present.
• Noting whether the diverter is properly sized and directs water into the gutter.
• Looking at the wall below for staining, cracking, swelling or soft spots.
• Checking interior surfaces and, where accessible, the attic or wall area behind the corner.
• Using a moisture meter on interior drywall, where the inspector carries one.

Home inspections are visual. An inspector will not cut into stucco or remove siding to confirm what is inside the wall, though some will note elevated moisture readings or suggest invasive moisture testing by a specialist, especially on stucco homes. Our home inspector hiring guide discusses how to ask what tools and methods an inspector uses, and the structure and exterior hub collects related topics.

What a missing kick-out finding means

A report noting a missing kick-out is common and does not by itself mean the wall is damaged. It is a recommendation to install the diverter and, depending on what else is visible, to evaluate the wall below. If there are stains, cracked stucco or soft spots, buyers often ask for further evaluation before closing so that any hidden damage is understood.

Retrofit and Repair Costs

Costs depend on cladding, access and whether damage is found. All figures below are general 2026 ranges for planning, not quotes.

Simple retrofit on siding

On lap or fiber cement siding with easy access, installing a kick-out often involves loosening a few siding courses, lifting a shingle or two, slipping in the diverter, integrating it with the step flashing and wrap, and reinstalling the siding. This is often a modest service-call job, sometimes in the low to mid hundreds of dollars per location, more if siding pieces need replacement.

Retrofit on stucco or stone

Cutting back stucco or stone, installing the diverter and weather barrier patch, and patching and color-matching the cladding usually costs more, commonly several hundred to well over a thousand dollars per location depending on the cladding and finish.

When damage is found

Rotted sheathing, framing, windows and drywall add significantly. Replacing a section of wall assembly at a corner can run into the thousands, and extensive stucco remediation can be much more. Mold cleanup, where needed, is an additional cost.

During reroofing or residing

The cheapest time to add kick-outs is during a roof replacement or new siding. Ask contractors to include a kick-out at every roof-wall termination as a line item, and confirm who is responsible for integrating it with the wall.

Steps for Buyers and Homeowners

1. Walk the exterior. Find each place a lower roof runs into a taller wall and check, from the ground, whether there is a visible diverter at the bottom.
2. Look below the corner. Stains, cracks and soft spots below the roof edge are worth a closer look.
3. Check inside. Look at the interior side of those walls for stains, bubbling paint or musty odors.
4. Watch during rain. Seeing where water actually goes during a storm, from a safe vantage point, can be revealing.
5. Keep gutters working. Clean them, fix leaky end caps, and extend downspouts away from the foundation.
6. Hire for the retrofit. Kick-outs involve roof, flashing and cladding work, and correct integration with the weather barrier matters more than the part itself.

A small diverter does not look like much, but a missing one can lead to costly hidden wall repairs. Adding it early, especially on stucco, is one of the more cost-effective preventive repairs a homeowner can make.

References

• ASHI Standard of Practice for Home Inspections — American Society of Home Inspectors
• A Brief Guide to Mold, Moisture and Your Home — U.S. Environmental Protection Agency
• Mold Cleanup in Your Home — U.S. Environmental Protection Agency

Seeing stains or cracked stucco below a roof corner on a home you are considering? Get in touch here to connect with a Front Range inspector who knows where hidden water damage tends to start.