Chimney Flashing Repair: Stopping a Chimney Leak
A leak beside the chimney is nearly always the metal where roof meets brick. The lasting repair is new flashing in two layers, not another bead of sealant.
What you may notice
A stain on the ceiling or wall right next to the chimney
Water or rust streaks inside the firebox or on the brick in the attic
Damp sheathing around the chimney opening when seen from the attic
Thick, cracked tar or caulk where the shingles meet the chimney
Flashing that has pulled away from the brick, or mortar missing above it
How soon it needs attention
It is rarely an emergency, but it does not get better. Each storm wets the framing around the chimney opening, and that wood is hard to reach and slow to dry. Have it repaired before the wet season if you can, and sooner if the stain is growing.
Chimney flashing repair, piece by piece
Chimney flashing repair deals with the joint where a sloped roof runs into a brick box. That joint is kept dry by metal in two layers:
- Step flashing: L-shaped pieces woven in with each course of shingles up the sides of the chimney, so every piece laps the one below.
- Counterflashing: a second layer fixed to the chimney that hangs over the step flashing. Done properly, its top edge is set into a cut in the mortar joint.
- Apron and back pan: wider pieces across the downhill and uphill faces.
- Cricket: on wider chimneys, a small ridge behind the chimney that diverts water to either side.
The two layers are separate on purpose. The roof and the chimney move differently, and overlapping metal lets them.
Why the quick fix does not hold
The common shortcut is to smear roofing cement or caulk along the joint. It works for a season or two, then cracks as the two surfaces move. Many chimney leaks are that old sealant failing. A lasting repair lifts the shingles around the chimney, installs new step flashing, and sets new counterflashing into the mortar.
Who does the work?
Flashing is roof repair, and it is routinely renewed during a roof replacement. If the stain is not right at the chimney, start with the general roof leak page. Published repair figures are on the cost page.
What causes it
A chimney is a hole in the roof with masonry in it. Step flashing, counterflashing and, on wider chimneys, a cricket are what keep water out of the joint. When sealant has been used in place of metal, or the counterflashing has pulled out of the mortar, water follows the brick down into the house.
Counterflashing that was surface-sealed to the brick instead of set into a mortar joint
Step flashing left in place and reused through one or more reroofs
No cricket behind a wide chimney, so water and debris pile up on the uphill side
Roofing cement used in place of metal, which cracks as it ages
Cracked mortar, a failed chimney crown or a missing cap letting water into the masonry itself
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Tell us about your roof and we pass your request to a local, CCB-licensed roofing contractor who can quote the work.
Common questions
Can chimney flashing be resealed instead of replaced?
Sealant can buy time on flashing that is sound and has only opened at a joint. It is not a repair for flashing that is rusted, missing or was never lapped correctly, and it will need redoing.
What does chimney flashing repair cost?
The cost page lists a published national range for flashing repair with its source and date. Rebuilding all the flashing around a large chimney, or adding a cricket, is a bigger job than that range's low end.
Is it the flashing or the chimney itself?
It can be either. Water also enters through a cracked crown, missing cap or open mortar joints and shows up in the same place. A roofer can check the flashing; masonry repairs are a mason's or chimney specialist's work.
What is a chimney cricket?
A small peaked structure built on the uphill side of a chimney to split the water and send it around both sides. Building codes call for one behind wider chimneys.
Should chimney flashing be replaced during a reroof?
That is the easiest time to do it, because the shingles around the chimney are already off. Ask whether the bid includes new step flashing and counterflashing at the chimney or reuses what is there.
Request a Roofing Quote
Tell us about your roof and we pass your request to a local, CCB-licensed roofing contractor who can quote the work.