Roofing services
Chimney flashing repair: the four parts that keep water out
Chimney flashing repair replaces the metal that seals the joint between a chimney and the roof: the apron at the front, step flashing up the sides, counterflashing let into the brick, and the back pan or cricket behind it.
Written by HyreRoof Research Desk Primary-source research and fact checking
The short answer
Chimney flashing repair replaces the metal that seals the joint between a chimney and the roof: the apron at the front, step flashing up the sides, counterflashing let into the brick, and the back pan or cricket behind it.
Most chimney leaks start at one of these four, and sealant smeared over the joint is a delay, not a repair.
If this is happening now
Do not go up to look. Chimney leaks show inside as stains on the ceiling or wall next to the chimney breast, and in the attic around the chimney. Report what you see from there.
What should you know about chimney flashing?
Base flashing turns up the chimney under the shingles. Counterflashing comes out of the mortar joints and laps over it. Water has to beat both.
Metal glued or caulked to the face of the chimney, rather than set into a cut mortar joint, is a common failure.
A small peaked roof behind the chimney that splits water around it. The code requires one above 30 inches wide.
Cracked crowns, porous brick and missing caps let water in from above. That is mason’s work, and a chimney inspection checks all of it.
Is it the flashing?
These point at the flashing rather than the chimney itself.
On the ceiling or wall, worse after rain from the uphill side.
Seen from the hatch with a flashlight, at the framing around the opening.
Someone has already patched it, often a sign the metal underneath has failed.
Visible from the ground with binoculars as metal standing proud of the brick.
Old steel flashing rusting through.
Flashing leak or chimney leak?
| Possible source | How to tell |
|---|---|
| Flashing | Water appears at the base, where the chimney meets the roof, and on the roof framing around it. |
| Cracked crown or missing cap | Water appears inside the firebox or flue, or runs down inside the chimney, often well above the roofline. |
| Porous or spalling brick | Damp patches on the chimney breast inside, white salt deposits (efflorescence) outside, and flaking brick faces. |
| Condensation in the flue | Staining that follows use of the appliance, not the weather. A chimney sweep or heating contractor should check it. |
What should the roofer check?
Apron, steps, counterflashing and back pan or cricket, each named in the report.
Above 30 inches, a missing cricket is itself the fault.
Let into a cut mortar joint, or surface-mounted with sealant.
Loose joints cannot hold new counterflashing.
Long-running leaks rot the wood around the opening.
Wood framing must keep its required gap from a masonry chimney. A roofer should flag framing that touches it.
How is chimney flashing replaced?
Shingles are lifted on all sides so the old metal can come out.
Rotten sheathing around the chimney opening is replaced.
Framed and sheathed behind the chimney, then covered in metal or the roofing material.
The apron at the front, one step flashing per shingle course up each side, and the back pan, all woven with the shingles.
A mortar joint is ground out, the counterflashing is set into it, and the joint is re-pointed or sealed as the maker directs.
With the shingles lapping the step flashing so water runs onto the roof, not behind the metal.
Which flashing metal?
| Metal | What it means for you |
|---|---|
| Galvanized or painted steel | Common on asphalt roofs. Rusts once the coating is worn or cut. |
| Aluminum | Does not rust. Ask whether the maker approves it where it meets masonry and mortar. |
| Copper or lead-coated copper | Long-lived and often used on slate and tile roofs and older masonry. |
Match the flashing to the roof covering’s life. A long-lived roof deserves flashing that will last as long.
What it costs: what the quote should itemize
Chimney flashing quotes vary most with what is found behind the old metal.
| Factor | Why it changes the number |
|---|---|
| Chimney size | More perimeter means more step flashing and more counterflashing. |
| Cricket | Framing, sheathing and covering, listed on its own line if needed. |
| Flashing metal | Steel, aluminum or copper, named on the quote. |
| Masonry work | Grinding joints, re-pointing and any crown or brick repair, often by a mason. |
| Deck rot | A per-sheet rate for sheathing around the opening. |
| Roof covering | Tile and slate take longer to remove and relay than asphalt. |
No price ranges yet, on purpose. HyreRoof publishes a price range for a job only once it holds at least 12 dated, sourced quotes for it, and we do not hold them for this work yet.
Until then, use the factors above to read a quote, and price your own numbers in the roof cost calculator or set quotes side by side in the estimate comparison tool. The cost guide explains every line.
Who does the work: roofer or mason?
The roofer owns the base flashing and cricket. The mason owns the brick, mortar, crown and cap. Counterflashing sits between them. Ask who is doing which part, and who answers for the leak if it comes back.
Questions to ask before you sign
Which, and why?
Or surface-mounted?
How wide is it?
Will it last as long as the roof?
You or a mason?
In writing.
Where does chimney flashing go wrong?
Sealant cracks as the chimney and roof move differently. It hides the gap for a season.
Continuous flashing up the side of a chimney on a shingle roof sheds water behind the shingles. Step flashing, one per course, is the method.
New metal will not fix a cracked crown. Rule out the masonry first.
Your inquiry
Tell us about the work
Nothing goes to a roofer unless you agree.
A person reads it and replies by email, free and with no obligation. Matching is not live yet, so this is not a quote. If water is coming in now, call a local roofer directly and check their license first.
Find a Roofer
One short form: your address and how to reach you. A person at HyreRoof reads it and replies.
Questions
How long does chimney flashing last?
Can chimney flashing be repaired without a new roof?
What is a chimney cricket?
Should the flashing be reused on a new roof?
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Information on this page is general and may vary by location, building code, roof design, insurance policy and your own circumstances. It is not insurance, legal or engineering advice.
HyreRoof is not a roofing contractor: we do not repair, replace or inspect roofs, and we do not supervise or warrant roofing work. This page explains the work so you can judge a quote and a contractor.