Chimney Repair & Flashing in the GTA
Chimney leaks almost always start at the flashing where the roof meets the chimney — not in the brick. Buildoreno traces the leak, re-flashes the chimney, and repairs the crown, cap, and mortar joints across Toronto and the GTA. We're roofers and masons, so the whole problem gets fixed in one trip — often bundled with a roof.
The number-one cause of a leaking chimney is failed flashing — the metal that seals the joint where the roof meets the chimney — not the brick itself. Re-flashing usually runs about $500–$1,500, a cracked crown or new cap roughly $300–$1,500, repointing or a partial rebuild around $1,500–$6,000+, and a full rebuild more. Buildoreno diagnoses the real leak source first, so you only pay for the fix you actually need.
Your chimney, part by part
A chimney is a small system, and leaks come from the seams between its parts far more than from the brick itself. The flashing seals it to the roof, the crown sheds water off the top, the cap covers the flue, and the mortar joints hold the masonry together. Get the vocabulary down and the diagnoser below — and your estimate — will make sense.
Step flashing tucks under each course of shingles against the chimney; counter-flashing is let into the brick mortar joints and laps over the step flashing. Done right it's a two-layer seal. When it rusts, lifts, or was just tarred over, this is where almost every chimney leak begins.
A small peaked structure built on the up-slope side of a wide chimney. It splits water and debris around the chimney instead of letting it pile up and pond behind it. Code generally calls for one on chimneys wider than about 30 inches — and missing crickets are a classic chronic-leak cause.
The sloped concrete (or mortar) cap across the very top of the masonry that sheds water off the chimney. It's not the same as the flue cap. Crowns crack with freeze-thaw, and a cracked crown lets water down into the chimney walls — a common, and fixable, leak source.
The metal cover with mesh sides that sits over the flue opening. It keeps rain, snow, leaves, birds, squirrels, and raccoons out of the flue. A missing or rusted-out cap lets water pour straight down the flue and lets animals nest inside.
The clay-tile, metal, or cast liner inside the chimney that safely carries smoke and combustion gases out. A cracked or missing liner is a safety issue, not just a leak one — water and acidic flue gases attack it over time.
The structure itself. Brick is porous and the mortar joints are the weak point — once they erode, water soaks in, freezes, and spalls (flakes) the brick face. Renewing those joints is called repointing, and it's how you stop water before it reaches the rest of the chimney.
Chimney leak diagnoser
Match what you're seeing to the likely cause below. The honest headline: most chimney leaks trace back to failed flashing where the roof meets the chimney, and the fix is often a $600 re-flash, not a rebuild. Crowns, caps, and mortar are the next most common culprits. This points you in the right direction — we confirm the real source on-site before quoting anything.
| What you see | Likely cause | Typical fix | Urgency |
|---|---|---|---|
| Water stain on the ceiling right around the chimney, worst after rain | Failed or rusted flashing (most common by far) | Strip and re-flash with new step + counter-flashing into the mortar | Soon — water is already inside the assembly |
| Dampness high up near the chimney top / inside the firebox | Cracked or deteriorated crown | Patch or recast the crown and seal hairline cracks | Moderate — gets worse every freeze-thaw |
| Water, leaves, or animals coming straight down the flue | Missing, rusted, or undersized cap | Install a properly sized stainless cap with mesh | Soon — also a nesting / draft problem |
| Brick faces flaking, popping, or crumbling | Spalling brick from freeze-thaw (water already soaked in) | Replace spalled brick + repoint and waterproof | Moderate — spreads if left wet |
| Crumbly, recessed, or missing mortar between bricks | Failed mortar joints — needs repointing | Grind out and repoint the joints, then seal | Plan ahead — it's the slow root cause |
| Ponding, debris, or a stain trail on the up-slope side of a wide chimney | No cricket / saddle diverting water around it | Build a cricket and tie it into new flashing | Moderate — chronic until diverted |
A leak can have more than one source at once, and water often travels before it shows. That's why we trace it rather than guess — and why we'll tell you when it's a simple flashing fix instead of selling you masonry you don't need.
Repair, partial rebuild, or full rebuild?
Most leaking chimneys need a repair, not a rebuild. If the masonry is still sound, new flashing, a recast crown, a cap, and repointing solve it. If only the top courses are failing, you rebuild the top — not the whole stack. A full rebuild is the honest answer only when the chimney is leaning, widely spalling, or more than roughly a third of it is deteriorated.
The masonry is sound but the seals or surface have failed. New flashing, a recast or patched crown, a fresh cap, and repointing the joints. This handles the large majority of leaking-chimney calls — and it's the honest first answer when the structure is still solid.
When the top few rows of brick above the roofline are spalling or leaning but the lower stack is solid, we take it down to good masonry and rebuild from there, then re-crown and re-flash. Far cheaper than a full rebuild and usually all a deteriorated chimney top needs.
Reserved for chimneys that are genuinely failing — leaning, with widespread spalling, or with more than roughly a third of the stack deteriorated. At that point patching is throwing money away. We rebuild from a sound base up, with a new crown, cap, liner as needed, and flashing.
- Less than ~1/3 of the stack is deteriorated → repair (re-flash, repoint, recap) almost always wins.
- The top courses are spalling or leaning but the base is solid → partial rebuild of the top, not the whole thing.
- More than ~1/3 deteriorated, leaning, or structurally unsound → full rebuild is the honest call.
Chimney repair pricing — typical GTA ranges
Ranges below reflect typical Buildoreno chimney flashing and masonry pricing for Toronto and the surrounding GTA in 2026. Re-flashing — the most common fix — runs about $500–$1,500, crown and cap work $150–$1,500, repointing $800–$3,000, and a partial or full rebuild from $1,500 up. Every quote is a free, itemized written estimate — these numbers are for planning, not a contract.
| Item | Unit / size | Price range | Notes |
|---|---|---|---|
| Chimney re-flashing | Step + counter-flashing | $500 – $1,500 | The #1 leak fix; cheapest done with a roof |
| Crown repair / recast | Concrete top | $300 – $1,500 | Patch hairline cracks or recast a failed crown |
| New chimney cap | Per flue | $150 – $600 | Stainless cap with mesh; keeps out rain + animals |
| Repointing | Per chimney | $800 – $3,000 | Grind out and renew failed mortar joints |
| Cricket / saddle | Wide chimneys | $300 – $1,200 | Diverts water around chimneys over ~30″ |
| Partial rebuild | Top courses | $1,500 – $4,000 | Rebuild deteriorated top, re-crown, re-flash |
| Full rebuild | Above roofline | $4,000 – $10,000+ | Leaning or >~1/3 of the stack failing |
Pricing includes materials, labour, and cleanup. Flashing, crown, cap, and repointing are itemized separately in every Buildoreno estimate so you only pay for what your chimney actually needs — and the flashing is far cheaper bundled with a roof.
Re-flash the chimney with the roof
Chimney flashing is the single most common roof-penetration leak source, and it should be fully re-done during any re-roof. Layering new shingles over old, tired flashing is exactly how leaks start a year or two after a roof job. When we're already on the roof, re-flashing the chimney, recasting the crown, and fitting a new cap cost far less than mobilizing separately — and proper new flashing outlives the shingle-tar patches a rushed roofer leaves behind. For crowns, repointing, and structural masonry, our general contracting crew handles the rest.
If your roof is due — or your eaves are also failing — it's almost always cheaper to handle the chimney at the same time. Here's where to go next.
Standing seam and metal shingles built to last 50 years — the right time to re-flash every chimney and roof penetration for good.
Explore metal roofingTPO, EPDM, and modified bitumen — chimney and curb flashing detailed into the membrane so penetrations stay watertight.
Explore flat roofingSeamless aluminum eaves, vented soffit, and fascia — the rest of the roofline, tied cleanly into the same flashing transitions.
Explore eavestroughCrowns, repointing, partial and full rebuilds — our general contracting crew handles the masonry side of the chimney.
Explore general contractingOur chimney repair process, step by step
- 01Inspection & leak trace
We get up on the roof and into the attic where we can, trace where the water is actually entering, and check the flashing, crown, cap, and mortar joints. You get an honest read on the real source — which is usually the flashing, not the brick.
- 02Tarp / temporary protection
If the leak is active and weather is coming, we tarp or temporarily seal the chimney first so no more water gets in while the permanent repair is scheduled. Stopping the damage comes before the finished work.
- 03Flashing & counter-flashing
We strip the old flashing and install new step flashing under the shingles with counter-flashing let into the mortar joints — a proper two-layer metal seal that outlives the shingle-tar patches most leaks were band-aided with.
- 04Crown, cap & repointing
We recast or patch the crown, fit a correctly sized stainless cap over the flue, and grind out and repoint failed mortar joints. On wide chimneys we build a cricket to divert water around the up-slope side.
- 05Waterproofing & sealing
Sound masonry is treated with a breathable water repellent so the brick sheds water without trapping moisture inside, and every flashing transition is sealed. This is what keeps a repaired chimney dry through GTA freeze-thaw cycles.
- 06Verification & walkthrough
We water-test the repair where practical, photograph the finished chimney, and walk you through exactly what was fixed and why. Workmanship is backed in writing.
Chimney repair FAQs
Nine times out of ten it's the flashing, not the brick. Flashing is the metal that seals the joint where the roof meets the chimney, and when it rusts, lifts, or was simply tarred over instead of installed properly, water runs straight in along that seam and shows up as a stain on the ceiling around the chimney. The other common culprits are a cracked crown (the concrete top), a missing cap letting rain down the flue, or eroded mortar joints soaking up water. We trace the actual entry point before quoting anything, because the fix for a flashing leak is very different — and usually far cheaper — than a masonry repair.
It depends on where the water is getting in, and that's exactly what an inspection settles. If the leak is at the roofline and the brick above is solid, you need flashing work — re-doing the step and counter-flashing — which is the most common chimney repair by far. If the brick faces are flaking, the joints are crumbling, or the crown is cracked, you're into masonry: repointing, crown repair, or rebuilding. Many chimneys need a bit of both. Because Buildoreno does roofing and masonry, we can tell you honestly which it is and fix the whole thing in one trip rather than sending you to two trades.
The rule of thumb is the amount of the stack that's deteriorated. If less than about a third of the chimney is damaged, repair almost always wins — re-flash, repoint, recap, and recast the crown as needed. If the top few courses of brick are spalling or leaning but the base is sound, a partial rebuild of just the top is the smart middle ground. A full rebuild is only the honest call when the chimney is leaning, widely spalling, or more than roughly a third gone — at that point patching is throwing money away. We'll show you what we see and recommend the least-invasive fix that actually lasts.
Repointing (sometimes called tuckpointing) is grinding out the old, failed mortar between the bricks and packing in fresh mortar. The brick itself usually outlives the mortar by decades, so the joints are where water finds its way in first. If the mortar lines look recessed, crumbly, sandy, or are missing in spots, the chimney needs repointing — and doing it before the water reaches and spalls the brick saves you a much bigger repair later. We match the new mortar to the existing joints and seal the masonry afterward.
Almost certainly, yes. A chimney cap is the metal cover with mesh sides over the flue opening, and it does three jobs: it keeps rain and snow from pouring straight down the flue, it stops birds, squirrels, and raccoons from nesting inside, and the mesh acts as a spark arrestor. A missing or rusted-out cap is one of the cheapest fixes on this page and one of the most worthwhile — it prevents both water damage and the very common problem of animals getting into the chimney. We size a stainless cap to your flue so it lasts.
Yes, and it's the smart way to do it. Chimney flashing should be fully re-done during any re-roof — the old flashing is at the end of its life and a new layer of shingles over old, tired flashing is exactly how leaks start a year or two later. When we're already on the roof, re-flashing the chimney, recasting the crown, and fitting a new cap cost far less than mobilizing separately, and proper new flashing outlives the shingle-tar patches a roofer in a hurry would leave. If your roof is due, doing the chimney at the same time is almost always the cheaper, longer-lasting choice.
Ready to stop
your chimney leak?
Book a free chimney inspection. We'll trace the actual leak, check the flashing, crown, cap, and mortar, and give you a straight answer on what needs doing — then an itemized written estimate. Bundle the flashing with a new metal or flat roof and save.
Call (647) 254-0877