Chimney flashing failures are the single most common source of residential roof leaks in the Chicago suburbs. We diagnose and repair flashing, tuckpoint deteriorated mortar joints, replace chimney caps, and handle masonry restoration for homes and commercial buildings across Cook, DuPage, and Lake Counties.
After thirty years of roof work in Chicagoland, chimney flashing is by far the most frequent source of the calls we get that start with "I have a roof leak but I don't know where it's coming from." The answer is usually the chimney. Not always the chimney itself — often it's the interface between the chimney masonry and the surrounding roof system that's the problem. That transition point, sealed by a layered flashing assembly, takes more mechanical stress than almost any other part of the roof. The chimney is rigid masonry. The roof deck moves with thermal expansion and contraction. Over years, that differential movement works at every sealant line and every metal overlap. Illinois winters accelerate it.
We repair chimney flashing and masonry on properties of all types — single-family homes, multi-unit residential, commercial buildings with brick parapets and chimney penetrations. The diagnostic process is the same: find where water is getting in, trace it back to the source, and fix it right the first time.
A chimney is the only structural element that passes completely through the roof plane. Every other penetration — a pipe boot, a vent, a skylight — has a relatively simple geometry. A chimney is different: it has four sides, multiple courses of flashing to manage, and often a saddle or cricket behind it to divert water around the wide back face. When any part of that system fails, water has a direct path into the roof structure.
The flashing system on a correctly installed chimney has several distinct components working together. Step flashing pieces interleave with the shingles along both sides of the chimney, directing water down and away from the masonry face. Counter flashing is embedded into the mortar joints of the chimney and laps over the top of the step flashing to prevent water from getting behind it. On chimneys wider than 30 inches, a saddle — sometimes called a cricket — is built behind the chimney to shed water that would otherwise pond against the back face and work its way under the shingles.
Any one of these elements can fail independently. Step flashing that wasn't properly interwoven with shingles will allow water to get behind it on the upslope side. Counter flashing that has simply been surface-caulked rather than embedded in the mortar joint — a common shortcut — will separate as the caulk ages. A saddle that was never built means water is pooling against the back of the chimney every time it rains.
The mortar joints in the chimney itself are a separate but related issue. Mortar is porous, and in Chicagoland's climate it's subjected to freeze-thaw cycling dozens of times per winter. Water enters hairline cracks, freezes, expands, and opens the crack wider. Over time, mortar that was once dense and sound becomes crumbly and recessed. When mortar joints are significantly deteriorated, water wicks through the chimney mass itself and can appear as interior moisture damage that seems unrelated to any flashing failure.
Step flashing consists of L-shaped metal pieces installed one per shingle course along the sides of the chimney. Each piece overlaps the one below it, creating a stair-step barrier. When step flashing is incorrectly installed, missing, or has lifted from the shingles, water bypasses it on the first heavy rain. We remove the surrounding shingles, replace the flashing with properly sized metal pieces, and reinstall the shingles over the top.
Counter flashing is the visible metal that covers the top of the step flashing and is anchored into the mortar joints of the chimney face. The mortar joint must be cut — not caulked — and the counter flashing embedded and sealed. Surface caulking fails within a few years in Illinois weather. We cut the joints, set the counter flashing properly, and seal with an appropriate elastomeric compound.
On chimneys wider than 30 inches, a saddle (cricket) is required behind the chimney to prevent water accumulation. It's a small peaked structure that diverts water to the sides rather than letting it pond against the back face. We build or repair saddles with metal flashing and shingles to match the surrounding roof surface.
We grind out deteriorated mortar joints to a consistent depth and pack in fresh mortar matched to the color and composition of the original. Tuckpointing restores weather resistance without the cost of dismantling and relaying brick. In Chicagoland, this is the standard maintenance repair for chimneys showing joint erosion or cracking.
A properly sized cap with a drip edge keeps rain, debris, and birds out of the flue. Caps deteriorate — the concrete cracks, the metal rusts — and a failed cap allows water into the flue liner, which saturates the interior masonry from inside. We replace caps in galvanized, aluminum, or stainless depending on the application and budget.
When spalling (surface flaking), freeze-thaw damage, or structural deterioration has affected the brick itself, we assess the extent and recommend appropriate repair. Minor spalling can be stabilized and sealed. Severely damaged sections may require brick replacement. Full chimney rebuilds from the roofline up are within our scope for residential and commercial properties.
Most chimney problems are detectable before they cause serious damage. Here's what to look for from inside and outside the house.
Brown or yellow staining on the ceiling or walls near a fireplace or chimney chase is the most common interior indicator. It often appears after rain rather than constantly, which points to a flashing or cap issue rather than a plumbing problem.
The white powdery deposits that appear on brick are efflorescence — mineral salts left behind when water moves through the masonry and evaporates at the surface. It's harmless in itself, but it indicates water is migrating through the chimney mass, which will accelerate deterioration.
If you can pick at the mortar joints with your finger or a key and material crumbles out, the mortar has deteriorated to the point where tuckpointing is needed. Visually, recessed joints — where the mortar has pulled back from the brick face — are a clear sign.
Surface flaking or flaking of brick faces is freeze-thaw damage. Water has entered the porous brick, frozen, and forced the surface layer off. Spalling tends to worsen each winter once it starts. Repointing and sealing can stop further deterioration.
From the ground with binoculars, or from a roofline view, look for metal that has pulled away from the chimney face, separated caulk lines, or step flashing that has lifted from the shingles. These are direct water pathways.
A persistent musty smell, especially after rain, indicates moisture is entering the flue. Common causes are a failed chimney cap, missing or damaged crown, or interior flue liner cracks. A flue inspection is warranted.
We don't seal problems from the outside and call it done. A proper chimney repair starts with understanding where water is actually entering before anything is removed or reinstalled.
We examine the flashing system, mortar joints, chimney cap, and the roof surface around the chimney. For active leaks, we trace the water path from where it appears inside back to the exterior entry point — these are often several feet apart. We also check the attic directly below the chimney for prior water damage to sheathing or framing.
We provide a written estimate before any work starts. If the repair involves both flashing and masonry, we scope each component clearly. If we find something unexpected during the repair — deteriorated decking, for example — we document it and discuss it before proceeding.
For a full reflash, we remove the surrounding shingles, strip the old flashing, and install a properly sized step and counter flashing system. The counter flashing is cut into the mortar joints — not surface-applied. The shingles are reinstalled to match, and the final seal is applied.
Tuckpointing is done in dry conditions above 40°F so the new mortar cures properly. We grind joints to a consistent depth, clean out debris, pack new mortar in lifts, and tool the joints to match the existing profile. The chimney crown and cap are addressed as part of this phase if needed.
We walk the completed repair before we leave. If there's any concern about a repaired area — particularly during wet weather — we're available to come back and verify. We document the work done, which is useful if you're filing a homeowner's insurance claim for storm-related damage.
Most chimney flashing repairs and masonry work on residential properties falls in the $1,500–$8,000 range. A targeted counter flashing repair or chimney cap replacement is on the lower end. A full reflash on a large chimney combined with tuckpointing the full chimney above the roofline is on the higher end. Full chimney rebuilds from the roofline up — necessary when structural deterioration is severe — run beyond that range and are priced individually.
If the chimney problem has allowed water into the roof deck, we'll assess that damage separately. Rotted sheathing or damaged framing adds cost, but addressing it at the time of the flashing repair is significantly more efficient than returning later.
We provide written estimates before any work starts. For storm-related chimney damage, we document the condition thoroughly, which is useful if you're working through an insurance claim.
The clearest sign is water staining on the ceiling or walls near the fireplace — especially after rain. You may also see rust staining on the exterior masonry below the flashing line, or notice daylight or gaps where the metal meets the brick. From the roof, look for flashing that has pulled away from the chimney face, visible caulk that has cracked and separated, or step flashing that has lifted from the shingles. Inside the attic, look for water marks or discoloration on the sheathing in the area directly below the chimney. None of these require you to get on the roof yourself — if you're seeing water intrusion near a chimney, that's enough to warrant a professional inspection.
Chimney flashing repair typically runs $500–$2,500 depending on the chimney size, the extent of the flashing failure, and whether any decking or sheathing has been damaged by water intrusion. A full reflash — removing the old system and installing new step flashing, counter flashing, and saddle — is more involved than a targeted resealing. Full chimney masonry repair or rebuilding, when needed, runs significantly higher. We give written estimates before any work starts.
Tuckpointing is the removal of deteriorated mortar from the joints to a depth of about 3/4 inch, followed by packing in fresh mortar. It's the standard repair for chimneys where the brick itself is sound but the mortar joints have eroded or cracked from freeze-thaw cycling. It preserves the original masonry and is significantly less costly than rebuilding. Full mortar replacement — essentially dismantling and relaying courses of brick — is only necessary when the mortar degradation is severe enough to have compromised the structural integrity of the chimney, or when the brick itself has spalled and failed. In Chicagoland, tuckpointing every 15–25 years is normal maintenance for a masonry chimney.
Yes. The most common chimney leak sources aren't visible to someone standing in the backyard looking up. Flashing failures — particularly where the step flashing meets the counter flashing — can allow water entry with no outward masonry damage at all. A chimney cap in poor condition allows water to enter the flue and saturate the interior masonry from the inside out. The porous nature of brick and mortar means water can wick through without a visible crack, especially on the north and west faces that don't dry out quickly in Illinois winters. If you're seeing interior evidence of moisture near a chimney, the problem is real even if you can't see the source from the ground.
For residential properties, a chimney and flashing inspection every 3–5 years is a reasonable interval if no problems are evident. Illinois weather — particularly the freeze-thaw cycling between November and March — accelerates mortar joint deterioration and works at flashing seals year after year. If a chimney has not been looked at in a decade, it should be inspected before the next winter. For commercial properties with multiple penetrations through a flat or low-slope roof, annual inspection of all roof-to-wall transitions including chimney and parapet flashings is standard practice.
Chimney flashing failures are the most common roof leak in Chicagoland. We'll find it and fix it.