Roof Flashing Inspection: Chimneys, Valleys and Sidewalls

Flashing is the metal that seals every place a roof plane meets something that is not more roof: a chimney, a wall, a valley, an edge. Add up the linear footage of flashing on a typical Macomb County home and it is a small share of the total roof area, yet flashing details are where a disproportionate number of leaks actually start. That is not a coincidence. A shingle field is one continuous, engineered surface designed to shed water. Every flashing detail is a deliberate seam in that surface, held together with metal laps, fasteners, and sealant instead of a single unbroken material, and seams are exactly where things eventually work loose. This guide walks through what an inspector checks at each major flashing type, what intact looks like next to what failed looks like, and the probe-and-sight checks that tell the difference. It stays on the inspection side of the line; if a check below turns up a failure, our roof repair page covers what fixing it actually involves.

01 / THE SHORT ANSWERWhat a flashing inspection actually checks

A thorough flashing inspection covers five details in sequence: chimney counter-flashing, step flashing at sidewalls, valley metal, drip edge at the eaves and rakes, and kick-out flashing wherever a roof edge meets a wall above a lower roof or gutter. Each one gets a visual pass and, where the metal is accessible, a physical probe, because flashing can look intact from a few feet away while the fastener holding it has already backed out or the sealant underneath has cracked.

Michigan's freeze-thaw climate is unusually hard on flashing specifically, because flashing relies on lap joints and sealant to stay watertight, and both move with temperature. Metal expands and contracts across the seasonal swing, sealant hardens and cracks with age and UV exposure, and any water that gets behind a joint before a freeze expands roughly nine percent as ice, prying the joint open a little further. A detail that would sit quietly for a decade in a milder climate gets worked loose here in a fraction of that time, which is why flashing deserves its own dedicated look rather than a quick glance folded into the shingle check.

02 / THE CHIMNEYChimney counter-flashing: what holds and what pulls loose

A chimney needs two layers of flashing working together. Step flashing at roof level sheds water away from the chimney base and up the sides, and counter-flashing, a separate strip of metal, tucks into a reglet cut into the mortar joints above and laps down over the step flashing to keep water from ever reaching the seam. When both layers are intact, water runs down the brick, over the counter-flashing, past the step flashing, and onto the shingles below without ever finding a gap.

Intact versus failed

Intact counter-flashing sits snug in its mortar reglet with no visible gap, and a gentle probe with a putty knife or gloved hand does not move it. Failed counter-flashing shows a visible gap at the mortar line, movement when probed, or a bead of caulk substituting for a properly seated strip of metal. Mortar erodes over the years, especially on older Macomb County chimneys, and as the joint opens, the counter-flashing that once gripped it loosens and eventually pulls away entirely, leaving only whatever sealant a previous repair added as a stopgap.

An inspector checks this by sighting the full perimeter of the chimney from the roof, then physically testing a few points along the reglet line rather than trusting a visual scan alone. Sealant smeared over a flashing gap can look fine from three feet away and still fail the probe test completely.

03 / SIDEWALLSStep flashing at sidewalls: one piece per course, no exceptions

Wherever a roof plane runs into a vertical wall, dormer, or second-story wall, step flashing does the work. Each piece is a small L-shaped rectangle of metal woven between shingle courses one at a time, so that every course has its own overlapping piece rather than one long strip trying to cover the whole run. Done correctly, water moving down the wall lands on metal at every course and is redirected onto the shingle below it, never reaching the nail line.

Intact versus failed

Intact step flashing is woven correctly, one piece per course, with no visible caulk substituting for metal anywhere along the run. Failed step flashing shows rust-through on individual pieces, a section where metal is missing entirely and a bead of sealant is doing the flashing's job instead, or pieces that were installed as one continuous strip rather than woven per course, which is a common shortcut on older or lower-quality work. A single rusted-through piece in an otherwise good run is enough to cause a leak at that exact course, so an inspector sights the full length of every sidewall rather than a sample of it.

04 / VALLEYSValley metal: the highest-volume water path on the roof

A valley is where two roof planes meet at an inward angle, and it carries more concentrated water flow than any other part of the roof, since runoff from both slopes funnels through the same channel. That volume makes valley condition disproportionately important to overall roof health, and it is one of the first places an inspector looks.

Intact versus failed

Intact valley metal is smooth, free of standing granules, and shows shingles trimmed cleanly back from the center line on both sides, leaving the channel open to move water. Failed valley metal shows visible corrosion or thinning, a buildup of granules and debris that traps water against the metal instead of letting it flow, or shingles cut too close to or overlapping the center line, which narrows the effective channel and forces more water under the shingle edges during heavy rain. An inspector checks both the metal condition and how much clear channel is actually left, since a valley can be structurally intact and still function poorly if debris has narrowed it over the years.

05 / EDGESDrip edge and kick-out flashing: the details homeowners never notice

Drip edge is the metal edging installed along the eaves and rakes, the outer perimeter of the roof, and its one job is directing water off the shingle surface into the gutter rather than letting it wick backward underneath the fascia. It is a small, inexpensive piece of metal, and it is also one of the most commonly missing or damaged items an inspector finds, because it sits at the exact point where wind, ice, and gutter work all have a chance to disturb it.

Intact versus failed

Intact drip edge sits flush and continuous along the full eave and rake line with no gaps, and it extends far enough over the fascia to direct water cleanly into the gutter. Failed drip edge is bent, pulled away from the roof edge, missing in sections, or simply absent because an older reroof skipped it, which lets water track backward under the shingles and stain the fascia board beneath. Winter is the hardest test: ice building at the eave has nowhere clean to go when drip edge is missing or damaged, and that is exactly the condition that lets meltwater back up under the shingle courses above it.

Kick-out flashing is the smallest and most overlooked detail on this whole list. It belongs at the bottom edge of any sidewall run, wherever a roof plane meets a wall above a lower roof section or directly above a gutter, and its job is to physically kick water outward into the gutter instead of letting it run down behind the siding at that exact corner. A missing kick-out is invisible from the ground and one of the more common causes of rotted sheathing hiding behind exterior siding at a wall-to-roof corner, discovered only once the damage has already spread.

06 / THE METHODWhy a probe-and-sight check beats a look from the ground

Every flashing type above shares one trait: a failure can be invisible from a distance and obvious the moment someone probes it. Sealant smeared over a gap, a piece of metal that looks seated but has already backed away from the mortar line, granules hiding a thinning valley channel, these all pass a casual glance and fail a hands-on check. That is the whole reason an inspection needs someone on the roof rather than binoculars from the driveway or a photo taken from a drone at altitude. Our drone versus walk-on inspection guide covers when each access method is appropriate, but flashing specifically is a zone where hands-on probing does something a camera cannot.

Flashing failures rarely travel alone, either. A cracked pipe boot near a valley, a missing kick-out at the bottom of a step-flashed wall, and a counter-flashing gap on the same chimney often show up together on an older roof, because they age on similar timelines. That is why a flashing check is only one piece of a full inspection rather than a standalone service, and it is checked alongside every penetration on the roof. Our roof penetration inspection guide covers pipe boots, vents, and skylight seals in the same depth, and the full 21-point inspection checklist shows exactly where flashing fits into the larger picture.

None of this diagnosis tells you what a failed flashing detail costs to fix. That is a separate question, and an honest one only a look at the specific damage can answer. Flashing and valley repairs generally fall inside our published $350 to $3,200 repair range, with a single reseated counter-flashing detail at the low end and a full valley rebuild or multi-point sidewall reflash toward the high end. What you actually need first is the inspection that tells you which one you are looking at, and that visit is free.

Timing matters here more than most homeowners assume. A flashing check right after a significant wind event catches lifted or displaced pieces before the next rain finds them, and a check going into fall, before the first hard freeze, catches sealant that has already dried and cracked over the summer but has not yet been forced open by ice. Neither visit needs to wait for a visible leak. Most of the flashing failures described above produce no interior sign at all for months, sometimes longer, because water tracks along the deck and rafters before it ever reaches drywall a homeowner can see. By the time a ceiling stain shows up, the flashing detail that caused it has usually been open for a while.

This is also why an inspector documents flashing condition even when nothing has failed yet. A counter-flashing joint that is still seated but shows early mortar erosion, or a valley with granule buildup that has not yet narrowed the channel enough to matter, are both useful things to have on record. They do not require action today, but they tell you what to watch, and they give the next inspection a clear baseline to compare against instead of starting from scratch.

A flashing detail that looks fine from the ground and fails the probe test is not a rare finding. It is the single most common thing we catch on roofs that otherwise look healthy.

Our inspectors check every flashing detail on this list on every visit, chimney, sidewalls, valleys, drip edge, and kick-outs, with a probe test wherever the metal is accessible, and the findings go into a written report with photos. If everything passes, the report says so. If something failed, you get a repair price, not a replacement pitch, and the inspection itself costs nothing to have run. Start one from the instant estimator, or if you are weighing what any resulting repair might run against a full reroof, the cost calculator uses the same published ranges as the rest of this site.