In short
- One Ottawa firm's guide prices flashing or vent repair at $400–$1,000.
- A Toronto firm's 2026 guide lists $400–$900 to replace step and counter flashing in aluminum, and $600–$900 more when done inside a re-roof.
- Flashing is the metal that seals a roof against a chimney, wall, skylight or valley; most chimney leaks start at its top edge.
- Caulk-only patches are a common repeat call; the same Toronto guide says they last roughly three to seven years.
- Structural repairs or alterations are on the City of Ottawa building permit list, so a leaning or crumbling chimney may need a permit.
Typical prices in Ottawa
| Job | Typical range | Notes |
|---|---|---|
| Flashing or vent repair | $400–$1,000 | Chimneys, vents, skylights; one Ottawa firm’s guide |
| Re-seal existing flashing | $250–$500 | One Toronto firm’s 2026 guide; Ottawa prices differ |
| Replace step and counter flashing, aluminum | $400–$900 | Same Toronto guide |
| Add a cricket behind a wide chimney | $600–$1,500 | Same Toronto guide |
| Flashing replaced as part of a re-roof | $600–$900 extra | Same Toronto guide, against $1,200+ as a standalone job |
Sources. JDM Roofing, Roof Repair Cost, an Ottawa firm’s list dated 16.10.2025, seen 29.10.2026. RenoHouse, Chimney flashing leak repair in Toronto, one Toronto firm’s 2026 guide, seen 29.10.2026 (Toronto prices shown for scale only). Permits: City of Ottawa, building permit projects, archived copy seen 29.10.2026 (lists structural repairs or alterations). Contracts: Ontario, guide for home renovation and roofing businesses, seen 29.10.2026. The company that calls you sets its own price after it has seen the roof.
Where chimney leaks begin
A chimney interrupts the roof. Water that runs down the slope meets a brick wall and has to be guided around it. Flashing does that job, in layers: step flashing woven into the shingles at the sides, an apron at the lower face, a back piece behind the chimney, and counter flashing set into the mortar and folded down over the top edge of the rest.
When the top edge opens, water runs behind the metal and out of sight. It stains the ceiling next to the chimney, and the stain often grows only in driving rain or a thaw. The same logic applies at sidewalls, vent pipes, skylights and valleys.
Why flashing fails
- Freeze-thaw on the mortar. The mortar joint that holds the counter flashing cracks, and the seal opens.
- Caulk as a patch. A bead hides the gap for a few seasons. One Toronto firm’s guide puts caulk-only repairs at roughly three to seven years.
- Mixed metals. Aluminum touching copper corrodes faster.
- Past re-roof shortcuts. Flashing caulked to the chimney face in place of being set into a cut joint.
- No cricket. On a wide chimney, snow and water pool on the uphill side.
What the repair involves
A full flashing repair takes out the counter flashing, lifts the step flashing, often with a few courses of shingles beside it, and cuts the mortar joint fresh. New step flashing goes in overlapping piece by piece. The new counter flashing is bedded in the joint and sealed along its top edge. A cricket gets added where the chimney is wide. A water test from above ends the job.
A re-seal is a lighter option that suits metal in sound condition. The roofer decides on site, and the quote should say which one you are paying for.
What drives the price
An Ottawa firm’s published guide puts flashing or vent repair at $400–$1,000 and an hourly rate of $60–$120. A Toronto firm’s 2026 guide breaks the work up: re-seal $250–$500, aluminum step and counter flashing $400–$900, cricket $600–$1,500. It adds that flashing replaced inside a re-roof adds $600–$900, against $1,200 or more as a standalone job. The Toronto numbers show how the work stacks up; Ottawa prices come from the company that calls.
Price moves with chimney size, roof pitch, metal choice, how many shingle courses must come up and whether the mortar needs repair. For wider repair pricing, see the roof repair cost page.
Chimney, permit and contract
The City of Ottawa’s building permit list includes structural repairs or alterations. Flashing alone is roofing work. If the roofer or a mason finds a leaning or crumbling chimney, the repair may fall under that item, so ask who checks with the City (3-1-1). The roofing permit guide has the contact route.
For the contract, Ontario’s guide asks for a written agreement over $50, an estimate that holds within 10% unless both sign a change, and a deposit no more than 10% of the cost as a recommendation. The contract page lists the rest.
Timing and Ottawa weather
Chimney leaks often show after heavy rain or spring melt. Ask the company what it can do in the weather you have now and what waits for milder days. If the roof is near the end of its life, ask for a price to do the flashing as part of replacement. The leak page covers tracing a stain that does not clearly sit by the chimney.
Who you are dealing with
An independent Ottawa roofer gets the photo and the stain location, inspects the flashing and quotes the fix. Going ahead is up to you.
Questions to ask the company
- Will you replace the flashing or re-seal it, and what is the difference in price?
- Is the counter flashing set into the mortar joint, or caulked to the face?
- Does my chimney need a cricket, and is that in the quote?
- Which metal will the flashing be, and does it match the other metals on the roof?
- Will you test the repair with water before you leave?
Have this ready for the call
- Ground photos of the chimney from two sides, with the roofline in frame
- The room and ceiling position of the stain, and which wall it is near
- How wide the chimney is along the slope, if you can measure it from the attic
- Any earlier flashing or caulking work at this spot, with the year
- Whether the chimney serves a fireplace, a furnace or a woodstove
Questions people ask
What are step flashing and counter flashing?
Step flashing is a row of small metal pieces woven with the shingles up the side of a chimney or wall. Counter flashing is a second strip, set into the masonry joint and folded over the top, so water cannot run behind the first. A leak at the top edge usually points to the counter flashing.
Why did the chimney leak again after caulking?
A caulk bead dries, shrinks and splits through freeze-thaw cycles. One Toronto firm’s guide says caulk-only patches last roughly three to seven years. If the metal is the problem, or the mortar joint behind it has cracked, caulk covers the symptom.
What is a cricket, and does my chimney need one?
A cricket is a small peaked roof built behind a chimney to shed snow and water around it. The same Toronto guide links the need to wide chimneys, over about 30 inches along the slope. The roofer measures yours and tells you if one belongs in the quote.
Is it the flashing, or is the chimney itself leaking?
Water can enter through cracked mortar, a damaged crown or the flue cap as well as the flashing. A roofer usually checks flashing first. Masonry work belongs to a mason, so the roofer may suggest one when the brick is the cause.
Is a skylight leak handled the same way?
Skylights have their own flashing kit, and many leaks come from old seals or the glazing. Replacement is a separate job, covered on the skylights page. Mention the skylight in your request so the company knows what it is looking at.