Step Flashing vs Reglet Flashing: Sealing Roof-to-Wall Transitions

Most roof leaks in metro Atlanta do not start in the open field of shingles. They start at the seams — the places where the roof plane runs into something it cannot simply cover. A chimney. A second-story wall. A dormer cheek. The point where a porch roof ties into the main house. These roof-to-wall transitions are where water concentrates, and they are where flashing earns its keep.

Two flashing methods do the heavy lifting at these transitions: step flashing and reglet flashing. They are often discussed as competitors, but on a real Atlanta home they are usually partners. Understanding what each one does, where each belongs, and how each fails is the difference between a roof that stays dry for thirty years and one that drips into a master bedroom ceiling after the third hard summer storm.

This guide walks through both methods in plain terms — how they work, when each is the right call, the failure modes our crews see most often on older Atlanta homes, and what a correct installation actually looks like in the written scope of a roof replacement. By the end you will be able to read a proposal and know whether the flashing detail has been respected or quietly skipped.

Why Roof-to-Wall Transitions Are the Weak Point

A field of shingles sheds water by overlap and gravity. Each course covers the nails of the course below, and water simply runs downhill across an unbroken plane. The system is elegant precisely because nothing interrupts it. The trouble begins wherever the plane ends against a vertical surface, because now water arrives at a wall and has nowhere obvious to go.

At that junction, three forces work against you. First, gravity carries the entire roof's runoff toward the lowest point of the wall intersection, concentrating volume. Second, in Atlanta's storm season, wind drives rain sideways and even uphill, pushing water under shingle edges and against the wall face. Third, the wall and the roof expand and contract at different rates through Georgia's swing from 20-degree January mornings to 95-degree July afternoons, so any rigid seal between them is under constant stress. Caulk cannot survive that. Mechanical flashing can.

Flashing solves the problem not by sealing the gap shut but by redirecting water. The metal creates a path that carries water back out onto the shingle surface before it can reach the wall sheathing or the framing behind it. This is the conceptual leap many homeowners miss: good flashing assumes water will get behind the cladding, and it gives that water a safe way back out. Bad flashing — or a bead of sealant standing in for flashing — tries to keep water out entirely, and loses the moment the sealant ages.

What Step Flashing Is and How It Works

Step flashing is a set of individual L-shaped (bent 90 degrees) metal pieces, typically 4 inches by 4 inches up to 5 inches by 7 inches, installed one per shingle course along a sloped roof-to-wall line. One leg lies flat on the roof deck, tucked beneath the shingle; the other leg stands vertically against the wall, behind the siding or cladding. Each piece overlaps the one below it, climbing the slope like stair treads — which is exactly where the name comes from.

The mechanics are simple and durable. When water runs down the wall or across the shingle toward the joint, it hits the vertical leg of a step piece and is turned back onto the flat leg, which sits on top of the shingle below. That shingle carries it to the next step piece, and so on down the slope until the water reaches the eave and the gutter. Because each piece is woven into a separate shingle course, no single failure point exists along the entire run. A nail in the wrong place compromises one piece, not the whole seam.

Correct step flashing has a few non-negotiable rules. The vertical leg must rise high enough up the wall — at least 2 inches, and more on steep pitches — to stay above the water line during wind-driven rain. Each piece must overlap the one below by at least 2 inches so there is no exposed seam. Critically, the fastener goes through the vertical wall leg only, high up, never through the flat roof leg where it would create a hole directly in the water path. We see face-nailed step flashing constantly on older Atlanta roofs, and every one of those nails is a future leak.

Step flashing is the correct method anywhere a sloped roof meets a vertical wall: dormer cheeks, the sides of a chimney, where a lower roof runs into a two-story wall, and the long sidewalls common on the traditional and craftsman homes throughout Marietta and Roswell. It is required by Georgia residential code and by every major shingle manufacturer's installation instructions as a condition of the material warranty.

What Reglet Flashing Is and How It Works

Reglet flashing — more precisely, counter-flashing set into a reglet — solves a different part of the same problem. A reglet is a groove. It is either cut into a masonry wall with a saw or formed into the surface (a "surface-mounted reglet" in some metal-panel and stucco systems). Counter-flashing is the metal piece whose top edge tucks into that groove and whose body laps down over the top of the step flashing or base flashing below it. Sealant fills the reglet to lock the metal in and shed water away from the slot.

The job of reglet counter-flashing is to cap the vertical legs of the flashing beneath it. Step flashing carries water down the roof, but its vertical legs against the wall have open tops. If water runs down the wall face, it could slip behind those legs. Counter-flashing overlaps them from above, like a raincoat sleeve over a glove cuff, so water on the wall is shed onto the outside of the step flashing rather than behind it. The reglet anchors the counter-flashing into the wall itself rather than relying on the wall surface.

Reglet flashing is the right method specifically where the wall is masonry: brick chimneys, stone and brick sidewalls, parapets on the flat and low-slope sections common in commercial roofing, and the brick-veneer walls found on so many of the estate homes in Buckhead and Alpharetta. On these surfaces you cannot simply tuck flashing behind cladding the way you can with siding, so the reglet gives the counter-flashing a permanent mechanical anchor cut into the masonry.

The cardinal sin with reglet flashing is the surface-mount-and-seal shortcut: bending the top of the counter-flashing flat against the brick face and running a bead of sealant along it rather than cutting a real groove. It passes inspection on a quick look. It fails within two to four Atlanta seasons as the sealant releases from the masonry under thermal movement, and the homeowner is left chasing a chimney leak that no amount of re-caulking will cure.

Step vs Reglet: A Head-to-Head Comparison

The comparison below frames the two methods on the dimensions homeowners ask about most. Read it less as a contest and more as a map of where each belongs — because on most Atlanta homes a complete chimney or sidewall detail uses both, with step flashing as the primary water mover and reglet counter-flashing as the cap.

The takeaway for an Atlanta homeowner is that the question is rarely "which one do I need?" It is "is the right combination present, and was each piece installed the way the method requires?" A frame wall with siding needs step flashing with a kickout at the bottom. A brick chimney needs step flashing woven against the brick and reglet counter-flashing cut into it on top. Skipping either half of that masonry detail is where leaks are born.

The Critical Companion: Kickout Flashing

There is a third piece that belongs in this conversation because its absence causes some of the most expensive damage we see: the kickout flashing. Where a step-flashed wall ends at the eave, the last piece of step flashing must be a specially formed diverter that "kicks" water out and away from the wall, into the gutter, rather than letting it run straight down behind the siding.

Without a kickout, every gallon that traveled down the step-flashed seam dumps directly against the wall at the eave, soaking the sheathing and the framing behind it. The damage is hidden — there is no ceiling stain, just slow rot inside the wall cavity that surfaces years later as failed siding, interior mold, or a structural repair. It is the textbook case of a small missing part causing major structural cost. We cover this detail in depth in our guide to kickout flashing and the wall rot it prevents, and it is a standard inclusion in every 1Source roof-to-wall detail.

If your home has a roof-to-wall intersection that terminates above a gutter — extremely common on Atlanta's two-story traditionals — checking for a kickout is one of the highest-value things an inspector does. Its absence is a near-certain source of slow water intrusion that an insurance adjuster will not cover once it is finally discovered, because it reads as long-term maintenance neglect rather than sudden storm damage.

Sealing a Chimney: Where Both Methods Meet

A masonry chimney is the clearest illustration of step and reglet flashing working as a system, and it is the single most common leak source on the Atlanta homes we re-roof. A properly flashed chimney has four distinct components, each doing a job the others cannot.

On the down-slope (front) face sits the base or apron flashing, a single bent piece that laps over the shingles below and up the chimney. Along each side, step flashing is woven course by course against the brick, climbing the slope. On the up-slope (back) side — where water piles up against the chimney — a saddle or cricket diverts the flow around the chimney rather than letting it pond against the brick. We explain that diverter in detail in our piece on chimney crickets and saddles. Then, capping all of it, reglet counter-flashing is cut into the brick on every face and folded down over the step and base pieces.

Each component is necessary. The step flashing moves water down the sides; the apron handles the front; the cricket prevents up-slope ponding; and the reglet counter-flashing caps the open tops of every vertical leg so wall runoff is shed outward. Remove any one of the four and the chimney leaks. The most frequent fault we correct is a chimney where someone replaced the entire assembly with a smear of black roofing cement — it looks sealed, holds for a season or two, then cracks and channels water straight into the firebox chase and the ceiling below.

Flashing Materials and Why Gauge Matters

Flashing is only as durable as the metal it is cut from, and material choice is one of the quiet ways a price-first contractor cuts a corner. The common options in metro Atlanta are galvanized steel, aluminum, and copper, and each has a place.

Galvanized steel is the workhorse for most residential step and counter-flashing. It is rigid, holds its bent shape well, and at a proper 26-gauge or heavier it lasts the life of the shingles. Thin 30-gauge galvanized, used to save a few dollars, dents during installation and corrodes faster at cut edges. Aluminum is lighter and naturally corrosion-resistant, which makes it popular, but it must never contact masonry mortar directly — the alkalinity in mortar corrodes raw aluminum, so it requires a coating or an isolating membrane where it meets brick. That detail is routinely missed.

Copper is the premium choice and the right one for the slate, synthetic-slate, and standing-seam metal roofs found on Atlanta's high-end estates. It develops a protective patina, never rusts, and outlasts almost any roof covering it serves. On a standing seam metal roof or a synthetic slate installation, pairing the roof with copper flashing protects the investment over the decades those systems are designed to last. Mixing dissimilar metals — copper flashing against aluminum gutters, for instance — must be avoided to prevent galvanic corrosion.

The Failure Modes We See Most on Atlanta Homes

After years of opening up roof-to-wall seams across metro Atlanta, the failures repeat with discouraging consistency. Knowing them helps you recognize a problem before it becomes a structural one.

Caulk in place of step flashing. By far the most common. A previous roofer ran a bead of sealant where the shingles meet the wall and called it done. It holds through one or two summers, then UV and thermal cycling crack it, and water pours into the wall. There is no fix except removing shingles and installing real step flashing.

Surface-mounted counter-flashing. The reglet was never cut; the counter-flashing was bent against the brick face and caulked. It fails the same way the caulked seam does, and the leak presents as a chimney leak that resists every re-seal attempt.

Face-nailed step flashing. Fasteners driven through the flat roof leg instead of the high wall leg. Each nail is a hole in the water path, sealed only by whatever shingle sits over it. As shingles age and lift, the nails weep.

Missing kickout. Covered above — the hidden rot-maker. No ceiling stain, just years of wall-cavity saturation.

Reused, mismatched flashing. Old flashing salvaged from a tear-off and forced back into a new shingle exposure it no longer fits. The overlaps are wrong and the seam telegraphs through within a year or two.

Every one of these is invisible from the ground, which is why a roof can look perfect from the driveway and still be feeding water into the structure. Tracking them down is exactly the kind of hidden-damage work that thorough inspection — including the drone inspection methods our crews use — is built to catch.

Signs Your Flashing Is Failing

You do not need to climb onto the roof to catch many flashing problems early. Several signs are visible from inside the house or from the ground, and noticing them early keeps a flashing repair from escalating into a deck or framing replacement.

Inside, watch for water stains on ceilings or walls near a chimney, a dormer, or anywhere a lower roof meets a two-story wall. Stains that appear specifically during wind-driven rain — not every rain — strongly suggest flashing rather than a field shingle problem, because wind is what pushes water past a marginal flashing detail. Peeling paint or soft drywall on the interior side of an exterior wall below a roof line is another classic flashing tell.

Outside, look for rust streaks running down a wall or chimney (corroding flashing), gaps or lifted metal at the roof-to-wall line, cracked or missing sealant at a chimney cap, and any visible roofing cement smeared along a seam — which usually means flashing was patched rather than replaced. Efflorescence, the white mineral crust on brick chimneys, signals chronic moisture moving through the masonry and frequently accompanies a failed reglet. When you see these signs, a flashing-focused inspection is the right next step before deciding between a targeted roof repair and a fuller solution.

Flashing Repair vs Full Replacement

Not every flashing problem demands a new roof. The right call depends on the age of the shingles, how widespread the flashing fault is, and what the surrounding materials look like once an inspector opens the area.

An isolated flashing failure on an otherwise sound, mid-life roof — a single chimney that was caulked instead of flashed, for instance — is a legitimate repair. The crew removes the affected shingles, installs proper step flashing and a cut-in reglet counter-flashing, and reintegrates new shingles. Done correctly, that repair lasts as long as the surrounding roof. The judgment call is whether the rest of the roof has enough service life left to justify the repair rather than rolling the flashing into a replacement.

When flashing failures are widespread, when the shingles are near the end of their service life anyway, or when the hidden damage behind the flashing has reached the decking or framing, a full replacement is the sounder investment. At that point, new flashing at every transition is part of the scope by default, and you avoid the false economy of repairing flashing under shingles that will need to come off in a few years regardless. Our broader guide on roof repair versus replacement walks through how to weigh the decision. Where storm activity caused the underlying damage, the flashing work often becomes part of a storm damage restoration and insurance claim rather than an out-of-pocket repair.

The 1Source Flashing Standard

Flashing is where roofing craftsmanship is either present or absent, and it is the part of the job a homeowner can almost never see. That is exactly why we make it explicit. Every 1Source roof-to-wall detail follows the same standard, and that standard appears in writing on the scope you review before you sign anything.

At every sloped roof-to-wall intersection we install new step flashing, woven course by course, fastened only through the wall leg, with a properly formed kickout at every eave termination. At masonry walls and chimneys we install new step and base flashing and then cut a true reglet into the brick or stone for the counter-flashing — never a surface-mounted, caulked substitute. Wide chimneys receive a cricket on the up-slope side. We match flashing metal to the roof system: galvanized or aluminum for asphalt, copper for slate, synthetic slate, and standing-seam metal. And we document the flashing line items in the written scope so you can confirm the detail rather than assume it.

This is the same standard whether the home is a ranch in Johns Creek or an estate in Sandy Springs, because the physics of a roof-to-wall transition do not change with the price of the house. The free assessment is where it starts: an inspector who knows exactly what to look for at every seam, a written record of what they find, and a scope that treats flashing as the structural priority it is. You can read more about our approach in our drip edge installation guide and across our roofing knowledge center, or learn why Atlanta homeowners choose 1Source.