ChimTech logo featuring a stylized chimney with an open book design in red and orange tones, topped with a bright flame in orange and yellow. The logo represents a chimney services company, combining imagery of fire safety and knowledge. The company name "ChimTech" appears below in bold white text on a dark background.
ChimTech logo featuring a stylized chimney with an open book design in red and orange tones, topped with a bright flame in orange and yellow. The logo represents a chimney services company, combining imagery of fire safety and knowledge. The company name "ChimTech" appears below in bold white text on a dark background.
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CHICAGO · CHIMNEY LEAK DIAGNOSTICS

Chimney Leak Inspection & Diagnostics in Chicago

Crown to flashing to mortar joints — we trace the full path in writing, for homes across Chicago and the surrounding suburbs.
Call (312) 768-8940
Book a Diagnostic
A chimney sweep professional scales a tall brick chimney using safety equipment and ropes while working on a snow-covered residential rooftop during winter. The technician is secured with climbing gear and is positioned against the chimney structure, with snow-laden roofs and a green residential house visible below. This image represents professional chimney maintenance and inspection services performed in challenging winter weather conditions.
READ THE SYMPTOM FIRST

Visible Symptoms That Point to a Chimney Moisture Entry Problem

Every moisture symptom points toward a specific structural location — not a general waterproofing problem.
None of these symptoms is the problem — each is a pointer. The visible sign almost never appears at the entry point: water enters at the top or along a flashing seam and travels through the structure before it shows up on your ceiling or in your firebox. That travel path is what the diagnostic uncovers.

Ceiling Stain Near the Chase

Usually means water traveled through the chimney's outer structure — not through the roof itself.

Damp Firebox After Rain

No ceiling stain, just moisture on the floor or back wall — often a failed cap or a cracked liner allowing direct entry.

White Powder on the Brick

Efflorescence: the salt residue left behind when water moves through the masonry and evaporates at the surface.

Musty Smell, No Fire

A musty smell from the firebox when you haven't burned suggests water has been sitting inside the system for a while.

March
Diagnostic Schedule Opens
Crown → Liner
Full Path Traced
Entry Point
Named in Writing
Diagnostic-Only
No Patching on This Visit
WHY SPRING IS PEAK SEASON

Why Chicago Snowmelt Makes Spring the Peak Season for Leak Discovery

Chicago snowmelt delivers concentrated water directly to chimney penetration points — most of it in March and April.
Snow accumulates on the roof through December, January, and February. When temperatures rise in late winter, that snow doesn’t drain evenly — it pools around the chimney base where the slope flattens at the penetration. Snowmelt infiltration hits flashing and crown surfaces with more sustained volume than any single rainstorm produces. A crack that barely admitted water during fall rains becomes a sustained entry point during a week of snowmelt.
This is why ChimTech opens the diagnostic schedule in March. Deposit patterns are freshest, moisture is actively migrating, and the path is still legible at the surface when we arrive. By July, the masonry has dried and the path is harder to read.
The winter freeze-thaw season also works against crowns and counter flashing — the upper layer of flashing embedded in the mortar joint that deflects water from the roof deck. Counter flashing embedded in eroded mortar has been loosening all winter; spring is when the gap becomes visible, and when we can trace it back to the water that showed up in your living room.
A worker in dark clothing stands on a dark asphalt shingled roof while secured with a safety rope, performing chimney or roof maintenance work. The residential roof features a black cylindrical vent pipe and is surrounded by evergreen and bare trees against a blue sky. Safety equipment including yellow and white markers are visible in the foreground, indicating proper fall protection protocols during this roofing service.
INSIDE THE INSPECTION

How ChimTech Conducts a Professional Chimney Leak Inspection

The sequence runs outermost surface inward — crown first, then cap, flashing, mortar joints, then liner.
Portrait of Brian Dobuis, founder of ChimTech
Brian Dobuis
Founder, ChimTech
A ChimTech service technician stands in front of a gray service van branded with the ChimTech logo and distinctive orange "A" symbols on a residential street. The technician, wearing a black ChimTech jacket and khaki pants, poses confidently beside the van in front of well-maintained brick and craftsman-style homes. The image represents professional chimney cleaning and maintenance services available for residential customers.
I’m Brian Dobuis, founder of ChimTech. When I arrive at a Chicago home for a leak inspection, I start on the ground with a visual survey of the full stack — crown condition from below, whether the cap is seated, whether flashing metal is visible or hidden, whether the upper mortar joints are recessed or intact. The ground view tells me where to focus once I am on the roof.
From the rooftop, I check the crown first. A hairline crack at the flue collar isn’t always visible until you are standing over it. A flush-poured crown without a drip edge — common on Chicago homes built before 1950 — absorbs water along its outer edge rather than shedding it. That water doesn’t enter immediately at the crack; it seeps along the crown-to-flashing path, the route moisture travels when a cracked crown migrates downward to the flashing layer below.
Step flashing — the L-shaped metal pieces woven between the chimney and roof shingles at the side joints — comes next, and I check each piece individually. Freeze-thaw separation at the mortar holding the counter flashing is the most common finding on older Chicago properties: when the mortar erodes, the counter flashing pulls away from the chimney face and water runs straight down the gap.
After the flashing layers, I work down the mortar joints, probing for soft spots — recessed joints on the upper courses are entry points even when no visible crack is present. Finally I check the interior: damper, smoke shelf, and liner from the firebox opening. Each observation goes into the written finding before I leave the roof.
What separates this from a repair visit is scope. The diagnostic is focused entirely on identifying and documenting the entry point — no patching, sealing, or remediation. The finding it produces is the document that drives the repair decision, whether that’s a crown replacement, a flashing reseat, or a mortar repoint. Book a repair before the entry point is confirmed and you risk addressing the wrong component.
THE DELIVERABLE

The Written Diagnostic Finding ChimTech Delivers After Every Inspection

Every leak inspection ends with a written finding that names the specific entry point — not a generic “seal the chimney.”
The document you receive identifies the precise structural location where water is entering, traces the moisture path from that entry point to where interior damage appeared, and states the specific repair service that addresses it. That specificity matters: a waterproofing application on a chimney with failed counter flashing doesn’t solve the problem — it coats the surface while water keeps entering through the gap behind the flashing.
The written finding also establishes a permanent record tied to this inspection. If you’re selling the home, it demonstrates the moisture concern was investigated and the structural source identified. If repair follows, the report connects the diagnostic to the repair record in a single chain of documentation.
ChimTech schedules leak inspections across Chicago and the surrounding suburbs — and the same crew that conducts the inspection carries out the repair once the entry point is confirmed in writing. Once documented, chimney leak repair in Chicago addresses the structural source directly.
WHAT WE CHECK

How ChimTech Works Through a Chimney Leak Diagnostic

The process works from the outside in — and produces a specific finding, not a general assessment.

Crown & cap condition — crack width, drip-edge presence, cap seating, and any gap allowing direct entry into the flue.

Counter flashing integrity — whether it's still embedded in the mortar joint or has separated; reglet condition.

Step flashing at side seams — each piece inspected for freeze-thaw separation, missing pieces, or improper lap.

Mortar joint depth — probed from the top course down; soft or recessed joints flagged as potential entry points.

Interior liner review — visual check from the firebox for moisture evidence, liner offset, or surface deterioration.

Written output — entry point named, moisture path documented, specific repair recommendation stated.

Waterproofing is not a first response to a leak. It seals the surface — and if an upstream entry point is still open, sealing the exterior traps moisture inside the masonry and accelerates freeze-thaw damage through the next winter. The diagnostic finds the entry point before any repair recommendation is made.
THE VISIT

The Diagnostic Visit from Exterior Assessment to Written Output

A defined sequence — ground assessment, rooftop inspection, interior review, written finding.
01

Ground & Rooftop Assessment

The visit begins with a full exterior view of the stack from grade — visible mortar recession, flashing gaps, and crown condition noted before any rooftop access. Rooftop inspection then covers the crown, cap, counter flashing, and step flashing in sequence, from the highest point downward.

02

Interior Inspection

Interior review covers the throat damper area, smoke shelf, and accessible liner from the firebox opening. Moisture evidence, debris patterns, and any visible liner surface changes are documented as the review proceeds.

03

Written Finding Delivered

Before leaving the property, ChimTech produces the written diagnostic output: it names the entry point, describes the moisture path, and states the specific repair service that addresses the source. You receive a documented finding — not a verbal summary — before scheduling any repair.

WHERE WE DIAGNOSE

Where ChimTech Locates Chimney Leak Sources Across Chicagoland

We trace leak sources across Chicago — and the surrounding suburbs.
The pre-1950 housing stock along corridors like Milwaukee Avenue through Avondale and Irving Park (60618) and the older blocks of Portage Park (60641) shows the highest rate of crown-to-flashing failure and eroded mortar joints — flush-poured crowns without drip edges and original step flashing that have been in service seventy years or more. Beverly (60643) and Oak Park present similar patterns, particularly on the two-story brick Georgians and greystones common to those blocks.
The combination of original construction details and decades of freeze-thaw exposure produces moisture complaints that need entry-point-specific diagnostics rather than surface treatments. ChimTech’s crew handles every leak inspection directly — no routing through a regional office, no outside diagnostic team.
AvondaleIrving ParkPortage ParkLogan SquareBeverlyHyde ParkOak Park
Call (312) 768-8940 to confirm your neighborhood and your visit window.
Aerial view of Minneapolis skyline showing downtown skyscrapers, the distinctive blue-roofed stadium, and the Mississippi River winding through the urban landscape with multiple bridges connecting different sections of the city surrounded by green parks and residential areas.

Book Your Chimney Leak Diagnostic Before the Entry Point Dries Out

Spring is the best time to trace a chimney leak — and ChimTech’s diagnostic schedule opens in March. Have your address and a brief description of what you’re seeing ready; we’ll confirm your visit window and deliver a written finding that names the moisture source before recommending any repair. Prefer email? Reach us at office@chimtech.org.
Call (312) 768-8940
FAQ

Frequently Asked Questions — Chimney Leak Diagnostics

A leak diagnostic is focused entirely on tracing and documenting where water is entering. It does not include patching, sealing, or any remediation — that’s repair work. The diagnostic produces the written finding that drives the repair decision, so the right component gets addressed. Booking a repair before the entry point is confirmed risks fixing the wrong thing.

Spring snowmelt delivers sustained water volume to chimney flashing and crown surfaces — more than any single rainstorm. In March and April the moisture is actively migrating and the path is still legible at the surface, so the entry point is easiest to trace. By July the masonry has dried and the path is much harder to read.

A stain near the chase usually means water traveled through the chimney’s outer structure rather than the roof itself. The visible sign almost never appears at the entry point — water enters at the top or a flashing seam and travels through the structure before it shows. The diagnostic traces that actual path to its source.

No — it’s a diagnostic-only visit that identifies and documents the entry point. The repair (a crown replacement, a flashing reseat, or an upper-course mortar repoint) is a separate step. The same Chicago crew can carry out that repair once the entry point is confirmed in writing.

Not as a first response. Waterproofing seals the surface, and if an upstream entry point is still open, sealing the exterior traps moisture inside the masonry and accelerates freeze-thaw damage through the next winter. The diagnostic finds the entry point first, before any repair — including waterproofing — is recommended.

A written finding that names the precise structural entry point, traces the moisture path from there to where the interior damage appeared, and states the specific repair that addresses it. It’s a permanent record tied to the visit — useful for a home sale, and it connects directly to the repair record if work follows.