Field guide · Sep 24, 2026

Leaking around the chimney? How to tell if it’s the flashing — and when repair is enough.

A chimney is a masonry box punched through your roof, and every side of it is a joint that has to shed water. When a stain shows up next to the chimney, the cause is usually one of a few things: failed step or counterflashing, an old tar patch, a cracked crown, or the brick and mortar themselves. Metro Detroit’s freeze–thaw cycles, ice dams, spring storms, and wind-driven rain work on all of them. Here’s how to tell them apart, and when a repair is all you need.

How chimney flashing is supposed to work

A properly flashed chimney has layers of metal that overlap like shingles, so water always runs down and out, never in:

Step flashing — L-shaped pieces along each side of the chimney, one per shingle course, woven in with the shingles.
Counterflashing — metal set into a mortar joint in the brick and bent down over the step flashing, so water running down the chimney face can’t get behind it.
Apron and back flashing — metal across the downhill front of the chimney and along the uphill back, where snow, leaves, and runoff pile up.

When any layer is missing, rusted, loose, or replaced with a smear of roofing cement, water finds the gap — often traveling along the framing, so the stain can appear a few feet from where the water got in.

Why chimneys leak in Metro Detroit

Counterflashing that was never cut in. Metal that is just caulked to the face of the brick depends entirely on the caulk. After a few winters of freeze–thaw, the caulk shrinks and pulls away, and water runs right behind the metal.
Tar patches. Roofing cement smeared over the flashing is the most common “fix” we find on chimneys. It can buy a season, but it cracks in the cold, traps water against the brick, and hides the real failure underneath.
Crown cracks. The concrete crown on top of the chimney sheds water away from the flue. Once it cracks, water gets into the masonry from above, freezes, and widens the crack every winter.
Brick and mortar. Brick and mortar absorb water. Eroded mortar joints and spalling (flaking) brick let water soak down inside the chimney, where it can show up in the attic or around the fireplace — even when the flashing is fine.
Snow and ice behind the chimney. Drifts on the uphill side melt slowly against the back flashing and turn small weaknesses into winter leaks.

What we found: tar where flashing should be

This before-repair photo is from a real job. Roofing cement has been smeared over the chimney flashing instead of the joint being properly flashed and sealed — the same kind of patchwork described above.

What we found before repair: a brick chimney on a gray asphalt shingle roof with the copper-colored flashing at its base smeared in black tar-like sealant instead of properly sealed, above a shingled valley, on an overcast day. — What we found: chimney flashing smeared with tar instead of properly sealed. This is the kind of patch we replace. Before-repair photo — Metro Detroit Roof Repair.

Flashing or something else? How to tell

Where and when the water shows up narrows it a lot:

Stain on the ceiling or wall beside the chimney, or wet framing at its sides in the attic — points to step or counterflashing.
Water inside the firebox, around the damper, or damp brick inside the house — points more toward the crown, the top of the chimney, or the masonry, not the roof flashing.
Leaks only during wind-driven rain from one direction — often a flashing gap on the side facing the storm.
Leaks only during snowmelt — could be snow piled behind the chimney, or an ice dam at the eave. Our guide on ice dam leaks covers that pattern.
Visible tar, caulk lines, or loose metal — check from the ground with binoculars or your phone’s zoom. Please don’t climb up to look.

Chimneys also sit near valleys, pipe boots, and vents, and a leak can have more than one source. Our guide to what a ceiling stain usually means walks through the usual suspects. When the clues don’t add up, our $189 leak diagnostic includes an attic check where accessible, a roof walk, and a water test if needed, with written findings and photos. It’s credited in full if you approve the repair the same visit.

When a repair is enough

A chimney leak is usually a problem with one detail, not the whole roof. A repair makes sense when the shingles around the chimney are still serviceable, the deck at the chimney is solid, and the masonry is sound enough to hold new counterflashing. From our published price book:

Step flashing repair, partial: $650–$950 — a failed section replaced and shingles woven back in.
Chimney reflash, standard: $950–$1,650 — new step and counterflashing on a typical masonry chimney, counterflashing cut into the mortar joint and sealed. Not a surface caulk job.
Chimney crown seal: $450 — cracked concrete crown cleaned and coated with elastomeric crown sealer.
Decking replacement, if rot turns up under the repair: $185 per sheet — quoted before we proceed, never a surprise on the invoice.

Chimney reflash and step flashing work carry our five-year flashing warranty, written on the invoice. The only things that change a price are the access modifiers on the price book, like a steep pitch or a second shingle layer.

Repair isn’t the whole answer when the brick itself is failing badly — crumbling mortar joints or spalled brick are masonry work, and new flashing needs sound masonry to seal against. If that’s what we see, we’ll show you in the photos. And if the roof around the chimney is truly at the end of its life, we’ll document that and refer you to a licensed installer. We don’t sell replacements, so there’s no reason to stretch a flashing job into a new roof.

What happens on a chimney flashing visit

On a reflash, we remove the tar and failed metal, weave new step flashing in with the shingles, and cut counterflashing into the mortar joint so it laps over the step flashing — then seal it. Every job gets a photo report: the old patch, the work in progress, and the finished joint.

If it’s leaking right now

Put a bucket under the drip, take photos, and stay off the roof. If a storm opened something bigger and more rain is coming, we can install an emergency tarp first and schedule the permanent repair after. Our first-hour guide for roof leaks has the full checklist.

FAQ: chimney leaks and flashing

Can I just put more tar or caulk around my chimney?

It may slow the leak for a season, but tar and caulk crack in Michigan freeze–thaw cycles and can trap water against the brick. The lasting fix is metal: step flashing woven into the shingles and counterflashing cut into the mortar joint and sealed.

How much does chimney flashing repair cost in Metro Detroit?

From our 2026 price book: step flashing repair (partial) is $650–$950, a standard chimney reflash is $950–$1,650, and a chimney crown seal is $450. If the source isn’t clear, the $189 leak diagnostic is credited in full when you approve the repair the same visit.

How can I tell if it’s the flashing or the chimney itself?

Water on the ceiling, wall, or attic framing beside the chimney usually points to the flashing. Water inside the firebox, around the damper, or on brick inside the house points more toward the crown or masonry. A diagnostic with a water test confirms it.

What warranty comes with a chimney reflash?

Chimney reflash and step flashing repairs carry our five-year flashing warranty, written on the invoice. You also get a photo report showing the finished joint.

Does a leaking chimney mean I need a new roof?

Usually not. Most chimney leaks come down to the flashing, a tar patch, or the crown. If the roof is truly at the end of its life, we’ll show you the photos and refer you to a licensed installer — we don’t sell replacements.

Call (586) 209-8910 Book an estimate Send photos / request a visit

Metro Detroit Roof Repair — repairs only. Flat rates. Photo report every job. Service-area business across Wayne, Oakland & Macomb. Licensed Michigan Maintenance & Alteration contractor 2101214735.