CHICAGO · CHIMNEY FLASHING REPAIR

Chimney Flashing Repair in Chicago

Counter flashing separation — not damaged shingles — is the most common source of chimney-related water intrusion in Chicago-area homes. We cut a fresh reglet and re-seat it properly, then document it.

TWO DIFFERENT SYSTEMS

Your Roof Was Fine. The Flashing Was the Problem.

A roof replacement stops water entering through the shingles — not through the gap between the counter flashing and the chimney face.

Counter Flashing

The upper layer — chimney work.

Embeds into a reglet channel cut in the mortar joint

Laps over the step flashing below it

Fails first — the reglet erodes under freeze-thaw

Step Flashing

The lower layer — roofing work.

Individual L-shaped pieces between shingle courses

Woven against the chimney side wall

Typically fails second, if at all

Together they form a two-layer water barrier where the roof meets the chimney — one sits on the roof deck, the other is anchored in the chimney’s mortar joint. When the mortar joint holding the counter flashing erodes, the flashing loses its grip and pulls away from the brick. A visible gap opens, and water runs straight down it into the roof deck below — regardless of how new the shingles are. That flashing work is also covered within ChimTech’s broader chimney leak repair service when a leak traces to the roof junction.

Counter Flashing

Fails First in Most Cases

Fresh Reglet

Cut — Not Caulked Over

Subzero–90°F+

Sealant Rated for IL

Written Record

Reglet · Material · Sealant · Date

WHY THE JOINT LETS GO

Chicago Chimneys and the Reglet Erosion Behind Flashing Failures

Winter moisture cycling attacks the mortar joint that holds counter flashing in place — and older Chicago homes feel it first.

The reglet is the horizontal channel cut into the mortar joint that receives and anchors counter flashing. Water absorbed into that joint freezes with each temperature swing, and repeated cycles across a single season progressively widen the reglet beyond the point where it can grip the flashing. The joint doesn’t fail all at once — it loses holding capacity gradually, season by season, until the gap appears. (The full mechanics are on our freeze-thaw chimney damage resource page.)

Chicago chimneys built before 1960 have worked through these conditions for six-plus decades, and the original mortar progressively loses depth in the reglet until the counter flashing has nothing left to grip. Chimneys on corner lots and on east-facing walls, where wind-driven rain off the lake hits the face directly, show erosion earlier than sheltered installations. For what the region’s older housing stock means across chimney components, see our older homes chimney resource page.

The fix is not caulk over the gap. The fix is cutting a fresh reglet and re-seating the flashing properly into sound masonry — work that overlaps directly with mortar repointing when the surrounding joints have eroded too. ChimTech handles it across Chicagoland without routing the work to a general roofing crew.

UP ON THE ROOF

What I Find When I Get on the Roof

By Brian Dobuis, Founder, ChimTech

Brian Dobuis

Founder, ChimTech

The call comes in mid-spring, after the snow clears. A homeowner on the Southwest Side had their roof replaced the previous fall — new shingles, new underlayment, new drip edge along the whole perimeter. The roofer did clean work. The ceiling stain came back in April anyway.

When I got up there, the shingles at the chimney base were fine and the step flashing looked intact at every course. The problem was the counter flashing — the metal piece that’s supposed to be seated in the mortar joint on the chimney face. It had pulled away from the brick by about three-eighths of an inch at the top seam. The original reglet had eroded to the point where the flashing had nothing holding it, and the caulk applied over it years earlier had cracked and separated. Water was running straight behind the flashing, down the face, and under the step flashing below.

The roof work was scoped correctly for what it was — shingle-level barriers are roofing work. The counter flashing and the mortar joint it sits in are chimney work. The gap between the two scopes was where the water got in. The repair: cutting a fresh reglet, re-seating the counter flashing into the new channel, and sealing it with a flexible, UV-stable compound rated from subzero January lows to 90-degree August afternoons. The joint location, flashing material, and sealant are all recorded in the job documentation.

WHAT YOU RECEIVE

What Documentation Do I Actually Receive?

Every flashing repair comes with a written job record specific to what was found and what was installed at that chimney.

Because the reglet sits inside a mortar joint, no future inspector or technician can determine what was done there without a written record of where to look and what material was placed. The record captures the reglet location on the chimney face, the flashing material installed, the sealant product and its rated temperature range, and the date of service.

The temperature rating is documented deliberately: an insurance adjuster evaluating a water claim near the chimney will want to know whether the sealant was appropriate for subzero conditions; a buyer’s inspector gets a material and location record rather than a gap in the service history; and a ChimTech technician returning five years later knows exactly what was installed and where to look for wear at the reglet line. That specificity is only possible in writing — and ChimTech provides it on every visit, without exception.

OUR STANDARD

ChimTech's Flashing Repair Standards

The correct materials, the correct sequence, and documentation that outlasts the visit.

Fresh reglet cutting — no attempt to re-anchor flashing into an eroded joint.

Flashing re-seated into the new channel before any sealant is applied.

UV-stable, flexible sealant rated for Chicago extremes — subzero to 90°F+.

Material-specific selection — stainless steel, aluminum, or copper matched to the existing installation where possible.

Step flashing inspection included — the lower layer is checked while we have access to the roof junction.

Written job record — reglet location, flashing material, sealant product, service date.

No shortcuts. No caulk-over-the-gap repairs. No work begins until the scope is stated in writing.

THE VISIT

From Diagnosis to Completed Documentation

Three stages — with no work performed before the scope is confirmed.

Flashing Diagnostics

ChimTech starts at the symptoms and works backward to the source — assessing counter flashing separation at the chimney face (measuring the gap, checking reglet depth, evaluating the mortar joint above and below the flashing seat) and inspecting step flashing at each course for secondary entry points. The assessment tells us exactly what needs to happen; we don't recommend repairs for components that are sound.

Re-Seating & Sealing

Once the scope is confirmed in writing, we cut a fresh reglet at the correct depth, re-seat the counter flashing into the new channel pressed flush against the face, and apply the flexible, UV-stable sealant over the reglet against freeze-thaw cycling, wind-driven rain, and summer heat expansion. If step flashing at any course shows separation or improper bedding, it's addressed in the same visit.

Post-Service Verification & Documentation

We verify the seal visually before leaving the roof, then complete the written job record on-site — reglet location, materials used, sealant product and temperature rating, and date of service. The homeowner receives a copy before we leave.

WHERE WE REPAIR

Where ChimTech Performs Chimney Flashing Repair

ChimTech performs flashing repair across Chicago and the surrounding suburbs — with the most volume in older neighborhoods where lime-mortar reglets have had the most cycles to erode.

Most flashing repair calls come from homes built before 1960 on the Northwest and Southwest Sides — Portage Park, Jefferson Park, Avondale, Irving Park, Logan Square, Beverly, and Norwood Park (zips 60618, 60630, 60641, 60643, 60647, and 60631 among them) — plus Berwyn and Oak Park, where original mortar joints have been through the most winters and reglet depth loss is most advanced.

Every flashing repair is dispatched directly from within the city — no routing through a regional office. The crew serving your address is the same crew that diagnosed the problem.

Southwest SidePortage ParkJefferson ParkAvondaleBeverlyNorwood ParkOak ParkBerwyn

Call (312) 768-8940 to schedule your flashing assessment.

Ready to Fix the Flashing?

Chimney flashing repair in Chicago starts with a documented diagnosis — not a guess and a caulk gun. Have your property address and a brief description of where you’re seeing moisture symptoms ready, and we’ll take it from there. Prefer email? Reach us at office@chimtech.org.

FAQ

Frequently Asked Questions — Chimney Flashing Repair

What is the difference between counter flashing and step flashing, and which usually fails first?

Counter flashing is the upper metal component embedded into a channel cut in the chimney’s mortar joint; step flashing is the individual L-shaped pieces woven between shingle courses and the chimney side wall. In Chicago, counter flashing fails first in the majority of cases because its anchor — the mortar joint reglet — erodes under freeze-thaw pressure. Step flashing typically fails second, either from improper original installation or from moisture that entered behind failed counter flashing and worked underneath it.

Can a roofer repair chimney flashing, or does it require a chimney specialist?

The step flashing at the shingle level is within a roofer’s scope. The counter flashing and the mortar joint reglet that anchors it to the chimney face are chimney masonry work. When a roofer addresses only the shingle-level flashing without touching the reglet, the counter flashing separation continues and so does the water entry. ChimTech handles both the reglet cutting and the counter flashing re-seating as chimney work, separate from the roofing scope.

Why can't the gap between the counter flashing and the chimney just be caulked?

Caulk over a failed reglet doesn’t restore the mechanical grip that holds counter flashing against the chimney face — the flashing keeps pulling away behind the caulk bead. Chicago temperature swings, subzero winters to 90°F summers, crack and separate the caulk within one to two seasons even with a quality product. The only repair that holds is cutting a fresh reglet and re-seating the flashing into the new channel.

How do I know if the flashing or the roof is causing the water stain inside my home?

The pattern of moisture entry is the starting point. If the stain appears at the ceiling directly adjacent to the chimney but the shingles are intact and the roof isn’t leaking elsewhere, the chimney-roof junction is the likely source — counter flashing separation lets water run behind the flashing and down the face, reaching the interior through the roof deck at that junction rather than through the shingles. A ChimTech assessment identifies the entry point precisely before any repair begins.

What materials does ChimTech use for flashing repair, and how long do they last?

ChimTech selects stainless steel, aluminum, or copper flashing based on the existing installation at each chimney, and the reglet sealant is a flexible, UV-stable compound rated for the full Chicago temperature range — subzero January lows through summer heat. Material selection and product used are documented in the job record. When the reglet is cut correctly and the flashing properly seated, a flashing repair here should remain watertight for a decade or more under normal conditions.

Does ChimTech inspect the step flashing as part of a counter flashing repair visit?

Yes. ChimTech inspects the step flashing at each course along the chimney side wall during every counter flashing repair. Because both systems are accessible from the same roof position, it makes no practical sense to address the counter flashing without verifying the step flashing below it. If step flashing has lifted or is improperly bedded at any course, that’s addressed in the same visit — and we don’t recommend repairs for courses that are sound.