Chimney Repair in Mississauga: What's Failing, What It Costs, and What to Fix First

Why Mississauga chimneys are failing right now

Mississauga grew explosively between 1975 and 1998 — Meadowvale, Erin Mills, Streetsville, Churchill Meadows, Lisgar, Heartland. Those homes were built with masonry chimneys and cast-in-place concrete crowns that carry a practical service life of roughly 25 to 40 years in Ontario. The city's housing stock has arrived at that number more or less simultaneously, which is why an entire street can show the same crown cracking in the same season.

The mechanism is always the same. A hairline crack forms in the crown. Water enters, freezes, expands about nine percent, and widens the crack. Next winter the cycle repeats — and in the GTA that cycle runs 40 to 60 times a season, not once. Within a few years water is reaching the top brick courses, dissolving lime out of the mortar, and saturating brick that then spalls its face off the next time it freezes.

The five repairs, in the order they should be done

1. Chimney cap — $180 to $650

The cheapest and most consequential part. A stainless steel cap with mesh keeps rain, snow, birds, raccoons, and squirrels out of the flue. A shocking number of Mississauga chimneys have none, or have a rusted galvanized one that has been dumping rust-stained water down the flue for years. Stainless with a lifetime warranty is worth the small premium; galvanized will fail again in eight years.

2. Crown rebuild — $850 to $2,200

The crown is the sloped concrete slab on top of the chimney. It should be cast concrete, at least 2 inches thick, sloped away from the flue, with a drip edge overhanging the brick by an inch and an expansion joint around the flue tile. Most builder-grade Mississauga crowns are none of those things — they are a thin skim of mortar troweled flush to the brick edge, which cracks and lets water straight into the wall. Rebuilding it correctly is the single most durable fix available.

3. Flashing — $650 to $1,600

Where the chimney meets the roof. Proper detailing means step flashing woven into the shingle courses and counter-flashing cut into a mortar reglet and sealed. If your flashing is a bead of black roof cement smeared where the brick meets the shingles, it is failing or already failed. Caulk is a maintenance item; correctly installed metal is a 30-year detail.

4. Repointing (tuckpointing) — $650 to $1,800

Grinding out deteriorated mortar to a consistent depth and packing in fresh mortar. On most Mississauga chimneys only the top three to five courses need it, because that is where wind-driven rain and crown failure concentrate the damage. Critical detail: the new mortar must be no harder than the brick. Modern Portland-heavy mix on softer older brick will transfer stress into the brick faces and accelerate spalling — a repair that causes the damage it was meant to prevent.

5. Waterproofing — $350 to $700

A breathable siloxane or silane masonry repellent applied after the repairs are done. It sheds liquid water while letting vapour escape. Never use a film-forming sealer on a chimney — it traps moisture inside the masonry and makes spalling dramatically worse.

Mississauga chimney repair prices, 2026

The liner question

Homes in Mississauga built before the mid-1990s often have a clay-tile flue serving a furnace or water heater that has since been replaced with a high-efficiency unit. High-efficiency appliances vent cooler, wetter exhaust, which condenses in an oversized masonry flue and attacks the tile and mortar from the inside. If you replaced your furnace and left the chimney alone, the flue may now be both oversized and deteriorating.

• Cracked or shifted clay tiles show up on a video scan and are a safety issue, not a maintenance item.
• An insulated stainless liner correctly sized to the appliance solves both the sizing and the deterioration problem.
• If the furnace now vents in PVC through a sidewall, the old chimney may only be serving the water heater — and may be badly oversized for it.
• Never accept a liner quote without a video scan showing the actual condition.

Hiring in Mississauga without getting burned

1. Get the diagnosis in writing with photos taken at your chimney, showing your roofline in frame.
2. Ask which mortar type they will use and why. A contractor who cannot answer should not be repointing brick.
3. Confirm $2M commercial general liability and WSIB clearance — ask for the certificates by email.
4. Require a written scope: number of courses, crown dimensions, flashing type and metal gauge.
5. Get the warranty in writing. Five years on repointing and ten on a crown rebuild is a reasonable GTA standard.
6. Be sceptical of door-knockers who 'noticed your chimney while working next door'. That is a script, not an observation.