How much does flat roof replacement cost in Ontario? In 2026, Ontario property owners can expect to pay between $8 and $25 per square foot for a full flat roof replacement, with most projects landing between $10,000 and $35,000 depending on roof size, material choice, and job complexity.
Flat Roof Replacement Cost by Material
| Material | Cost/sq ft | Lifespan | Best For |
|---|---|---|---|
| Modified Bitumen | $8–$14 | 15–25 yrs | Residential, mid-size commercial |
| EPDM (Rubber) | $8–$16 | 20–30 yrs | Cold climates, large commercial |
| TPO | $10–$18 | 20–30 yrs | Energy efficiency, warehouses |
| PVC | $12–$22 | 25–35 yrs | Restaurants, industrial |
| Built-Up (BUR) | $10–$16 | 20–30 yrs | Proven multi-layer system |
| Spray Foam (SPF) | $12–$20 | Recoat 10–15 yrs | Avoiding tear-off, insulation |
Modified bitumen is Ontario's most common flat roofing system — combining asphalt with rubber polymers for excellent cold-weather waterproofing. EPDM rubber roofing excels in extreme cold, making it ideal for Ontario's harsh winters. TPO is increasingly popular for commercial flat roof replacement due to energy efficiency and UV reflectivity. PVC is the premium option with the best chemical resistance and fire rating.
Cost by Roof Size
| Roof Size | Cost Range | Building Type |
|---|---|---|
| 1,000 sq ft | $8,000–$18,000 | Small residential, garage |
| 2,000 sq ft | $16,000–$36,000 | Average commercial |
| 3,000 sq ft | $24,000–$54,000 | Mid-size commercial |
| 5,000 sq ft | $40,000–$90,000 | Large commercial/industrial |
| 10,000+ sq ft | $80,000–$150,000+ | Warehouse, distribution |
Cost by Ontario City
| City/Region | Cost/sq ft | Notes |
|---|---|---|
| Toronto & GTA | $12–$25 | 15–25% above provincial avg |
| Ottawa | $10–$20 | Moderate pricing |
| Hamilton & Niagara | $9–$18 | Competitive pricing |
| London / KW | $8–$16 | Lower overhead |
| Northern Ontario | $10–$20 | Higher transport costs |
What's Included in a Quote
A complete flat roof replacement quote should include: tear-off and disposal, roof deck inspection and repair, new vapour barrier, new insulation (typically polyiso), new membrane, flashings around all penetrations, drip edge and perimeter metal, clean-up, and warranties.
Key Cost Factors
Number of Existing Layers
Multiple layers add $1–$3/sq ft in removal costs. Ontario building codes require full tear-off when more than two layers exist.
Roof Access & Building Height
Difficult access on downtown Toronto row houses or multi-storey commercial buildings can add 15–30% to project cost.
Insulation Requirements
Ontario Building Code requires approximately R-31 for most commercial flat roofs. Upgrading during replacement can reduce heating costs 10–20%.
Structural Repairs
Deck replacement costs $3–$6/sq ft for plywood or $5–$10/sq ft for steel deck repairs.
Repair vs. Replacement
Repair when damage is localized (<15% of roof), roof is under 15 years old, and moisture survey shows <25% wet insulation. Replace when leaks recur in multiple locations, roof has exceeded its lifespan, or moisture survey shows >25% wet insulation.
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Pricing data as of March 2026. For a personalized quote, visit roofrfq.ca.