Chimney Flashing Repair: Leak Signs, Crickets and Costs

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A chimney is a large masonry box punched through the roof, and the joint where brick meets shingles is one of the most leak-prone spots on any house. Metal flashing is what keeps that joint dry. When the flashing is loose, rusted, poorly installed or covered in cracked caulk, water can run down the outside of the chimney and into the attic, ceiling or walls below. This guide explains how chimney flashing is supposed to work, the signs that it is failing, the difference between a quick sealant patch and a proper chimney flashing repair, masonry problems that look like flashing leaks, rough costs and whether to call a roofer or a chimney professional.

Part of our Structure & Exterior guide — start there for the full picture →

How Chimney Flashing Works

Chimney flashing is a set of overlapping metal pieces that bridge the gap between the roof covering and the chimney masonry. It has to shed water while allowing the house and chimney to move independently. A chimney typically sits on its own foundation, while the roof framing expands, shrinks and settles separately, so a rigid seal between the two would crack. Instead, flashing relies on layers that overlap like shingles, so gravity carries water outward and downward.

The American Society of Home Inspectors Standard of Practice lists flashing, skylights, chimneys and roof penetrations among the items a home inspector inspects under roofing. In practice, the chimney-to-roof joint is a routine focus of the roof portion of an inspection, especially on older homes where flashing may be original.

Step Flashing

Along the sides of the chimney, individual L-shaped pieces of metal are woven in with each course of shingles. One leg lies on the roof under the shingle above it; the other leg turns up against the brick. Because each piece overlaps the one below, water that runs down the side of the chimney is passed from piece to piece and onto the top of the shingles. The roof flashing guide covers how the same principle applies at walls, dormers and skylights.

Counter Flashing

Step flashing alone would leave its top edge exposed against the brick, where water could run behind it. Counter flashing (also called cap flashing) covers that edge. It is usually set into a saw-cut groove in a mortar joint, bent down over the step flashing and sealed into the groove. On the sides, it is often cut in a stair-step pattern to follow the mortar lines. The two layers are not fastened together, which lets the roof and chimney move without tearing the seal.

Apron and Back Flashing

The downhill face of the chimney gets a continuous apron flashing that laps over the shingles below. The uphill face is the hardest part, because water and snow sliding down the roof run straight into the back of the chimney. A back pan or saddle flashing turns up the brick and runs under the shingles above, again covered by counter flashing.

Crickets (Saddles) on Wide Chimneys

On wider chimneys, a cricket, also called a saddle, is built on the uphill side. It is a small peaked roof that splits water and snow and diverts them around both sides of the chimney instead of letting them pond against the back. Many building codes and roofing manufacturers call for a cricket when the chimney is wider than about 30 inches measured parallel to the ridge, though local codes vary. Crickets are framed in wood and covered with membrane and either metal or shingles. On the Front Range, where snow can drift and sit behind a chimney for days, a missing cricket on a wide chimney is a common cause of recurring leaks.

Signs of a Chimney Flashing Leak

Flashing leaks often show up far from where the water enters, and they may appear only during wind-driven rain or snowmelt. Common signs include:

• Water stains on the ceiling or walls next to the chimney or fireplace, often in a top corner of the room.
• Damp, stained or dark framing and roof sheathing around the chimney when viewed from the attic.
• Peeling paint or bubbling drywall on the chimney breast inside the house.
• Rusty nail tips, damp insulation or mold on the decking near the chimney.
• Visible gaps, lifted edges, rust holes or missing pieces of flashing from the roof or with binoculars from the ground.
• Thick layers of caulk, tar or roofing cement smeared over the flashing, which usually means someone has patched it before.
• Counter flashing that has pulled out of the mortar joint or is held only by sealant.

The attic is the best place to look. Checking with a flashlight during or shortly after a storm or a warm afternoon of snowmelt is often more revealing than a dry day inspection. The roof leak guide covers how to trace water back to its entry point.

Slow, repeated leaks can cause hidden damage. The EPA’s guide to mold and moisture notes that wet or damp materials should be dried within 24 to 48 hours after a leak, and that if mold is cleaned up but the water problem is not fixed, the mold problem will most likely come back. Rotted roof decking, damp insulation and stained framing around a chimney are common findings once a flashing leak has gone on for several seasons.

Sealant Patches vs Proper Reflashing

When a chimney leaks, the quickest response is often a tube of roofing sealant or a coat of tar around the joint. That approach may stop water for a season, but it has real limits.

Why Caulk-Only Fixes Fail

• Sealant is exposed to sun, heat and freeze-thaw cycles, and Colorado’s high-altitude UV breaks it down quickly.
• The roof and chimney move independently, so a rigid bead of sealant bridging the two eventually cracks.
• Sealant applied on top of the flashing can trap water behind it instead of letting it drain.
• Thick patches hide the condition of the metal and brick, making the next diagnosis harder.

Sealant has a proper role: a high-quality, compatible sealant is used where counter flashing enters the mortar groove and at a few other points. The problem is relying on it as the main barrier.

What Proper Reflashing Involves

A full chimney flashing repair usually means removing shingles around the chimney, pulling out the old step and counter flashing, installing self-adhered membrane on the deck around the chimney, installing new step flashing course by course, setting a new apron and back pan, building or rebuilding a cricket if needed, cutting fresh reglets into the mortar for the counter flashing, and reshingling. Metal choices include galvanized steel, aluminum, copper and pre-finished steel; copper is long-lived but costs more, and aluminum should not be in direct contact with fresh mortar unless it is coated, because the alkaline mortar can corrode it.

When the roof is being replaced anyway, the chimney should be reflashed at the same time. Reusing old flashing with new shingles is a common shortcut that can lead to leaks shortly after a new roof goes on.

Partial Repairs

Not every leak needs a full reflash. Resetting a section of counter flashing that has pulled out of its groove, replacing a damaged apron or adding a missing piece of step flashing can sometimes solve a specific problem. A good contractor will explain what failed and why a partial repair is or is not appropriate.

Flashing on Other Roof Coverings

The same layered principle applies on other roofs, with different details. On standing-seam metal roofs, the chimney is usually wrapped with custom-bent pans and curbs that let panels expand and contract, and a cricket is often formed from matching metal. On concrete and clay tile roofs, the flashing sits under and around the tile, with lead or soft metal dressed over the tile profile, and broken tile near the chimney can expose the underlayment. Wood shake and slate roofs need flashing that will last as long as the roofing itself, which is one reason copper is popular there. A roofer familiar with the specific material is the right person for these jobs, because a shingle-style repair on a tile or metal roof can create new leak paths.

Questions to Ask Before Approving a Repair

• Will the old step flashing be removed and replaced, or only covered?
• How will counter flashing be attached: cut into the mortar, surface-mounted with a termination bar, or something else?
• Is a cricket needed, and is it included in the price?
• Will self-adhered membrane be installed on the deck around the chimney?
• What is the workmanship warranty, and does the work affect any existing roof warranty?

Masonry Problems That Mimic Flashing Leaks

Not every leak around a chimney is a flashing problem. Masonry absorbs water, and several defects can let water into the chimney itself, where it travels down and appears in the same places a flashing leak would.

• Cracked or missing chimney crown. The crown is the concrete or mortar cap on top of the masonry. Cracks let water soak straight down into the brick and flue area. The chimney crown repair guide explains crown construction and repair.
• Missing chimney cap. Without a cap over the flue, rain and snow fall directly into the chimney.
• Deteriorated mortar joints. Eroded or cracked mortar lets water in through the sides of the chimney, and loose joints can also let counter flashing work free.
• Spalling brick. Brick that has absorbed water and been through freeze-thaw cycles can flake and crumble, opening paths for more water.
• Porous brick. Some brick and mortar absorb a lot of water in wind-driven rain. A breathable masonry water repellent is sometimes recommended, though it should not be used to mask structural or flashing defects.
• Condensation in the flue. Older chimneys serving gas appliances, especially unlined or oversized flues, can develop condensation that stains the chimney breast. This looks like a leak but comes from inside.

Because the symptoms overlap, a careful diagnosis looks at the crown, cap, masonry and flue as well as the flashing. A water test, with one person running a hose on specific areas while another watches in the attic, can help isolate the source.

Roofer or Chimney Professional?

Chimney flashing sits on the boundary between two trades, and that can cause confusion.

• Roofers are usually the right call for step, apron and back flashing, crickets and leaks tied to the shingles around the chimney. They are also the natural choice when flashing is being replaced as part of a reroof.
• Chimney sweeps and masonry contractors are usually the right call for crowns, caps, mortar repointing, spalling brick, flue liners and anything involving the interior of the chimney. Many also install counter flashing.

Some companies do both. The best outcome comes when whoever does the work coordinates the counter flashing and the step flashing as one system rather than patching only the piece within their trade.

Fuel-burning chimneys need regular attention regardless of leaks. The U.S. Fire Administration advises having heating equipment and chimneys cleaned and inspected each year by a professional. Chimney professionals commonly describe inspections in three levels, a framework that comes from the NFPA 211 standard: a basic visual check for chimneys in continued use, a more detailed inspection typically recommended at a property sale or after a change to the system, and an invasive inspection when hidden damage is suspected. The chimney inspection guide explains what each level usually covers. A detailed inspection before buying a home with a fireplace can catch flashing, crown and flue problems at the same time.

Roof work around a chimney is also physically risky. OSHA notes that falls are among the most common causes of serious work-related injuries and deaths and requires fall protection in construction at six feet. Homeowners are better off inspecting from the ground and the attic and leaving roof-level work to equipped contractors.

Chimney Flashing Repair Cost

Prices vary with the chimney’s size, roof pitch, roofing material, metal type and local labor rates, so treat these as broad, hedged ranges rather than quotes:

• Minor repair or resealing: resetting counter flashing or sealing a small section may cost roughly $200 to $600.
• Full reflashing of a typical chimney: many homeowners see quotes in the range of about $800 to $2,500 with standard metals on an asphalt shingle roof.
• Adding or rebuilding a cricket: often adds several hundred dollars to $1,500 or more, depending on size and framing.
• Copper flashing, tile or slate roofs and steep pitches: can push totals well above those ranges.
• Related repairs: rotted decking, interior drywall and paint, insulation replacement and masonry repair are usually extra.

Asking for a written estimate that lists each flashing component, the metal type and gauge, whether a cricket is included and how the counter flashing will be attached makes bids easier to compare. On the Front Range, roofers get busy after hail seasons, and scheduling may take longer in late spring and summer.

Chimney Flashing and the Home Inspection

During a pre-purchase inspection, the inspector will typically look at the chimney from the roof surface, from a ladder or with a drone or binoculars, depending on height, pitch and conditions, and then check the attic around the chimney where accessible. Typical findings include rusted or loose flashing, sealant-only joints, missing crickets on wide chimneys, cracked crowns, missing caps, deteriorated mortar and stains in the attic. The ASHI Standard of Practice does not require inspectors to inspect the interiors of flues and chimneys that are not readily accessible, which is one reason a separate chimney inspection is often recommended for homes with fireplaces or wood stoves.

Buyers who see a flashing note in a report may want a roofer or chimney professional to provide a written estimate before their inspection objection deadline. The guide to hiring a home inspector explains how to scope an inspection, and the structure and exterior hub gathers related guides on roofing, masonry and drainage.

Homeowners can reduce future problems by checking the attic around the chimney every fall, keeping the area behind the chimney clear of debris, watching for snow buildup behind wide chimneys and having flashing checked whenever the roof is serviced.

References

• ASHI Standard of Practice for Home Inspections — American Society of Home Inspectors
• Heating Fire Safety — U.S. Fire Administration
• A Brief Guide to Mold, Moisture and Your Home — U.S. Environmental Protection Agency
• Fall Protection Overview — Occupational Safety and Health Administration

Looking at a Front Range home with a fireplace and worried about the chimney? Reach out through our contact page and we can connect you with a local inspector who looks closely at flashing, crowns and the attic around them.