The primary cost variables for flat roof replacement in Gatineau are: surface area in square metres, number of membrane layers to remove, condition of the roof deck (rot or damage adds material and labour), amount of rigid insulation being added or replaced, complexity of penetrations and flashings, and drain configuration. Cossette provides itemized estimates that make each cost component transparent.
Cost by Roof Type in Gatineau (2025–2026 Estimates)
Residential garage or addition (30–50 m²): $2,500–$6,000. Residential flat roof section over living space (50–100 m²): $4,500–$12,000. Commercial flat roof (500+ m²): Priced by project scope — contact Cossette for a commercial estimate. These ranges include tear-off, deck inspection and repair where needed, two-layer SBS installation, flashing replacement, and taxes.
The Cost of Delaying Flat Roof Replacement in Gatineau
A failing flat roof doesn’t just need replacing — it causes interior damage that compounds the total cost. Water-damaged insulation, rotted roof deck sections, and ceiling/drywall repair can double or triple the total remediation cost compared to proactive replacement before failure. When a flat roof shows widespread cracking or has had multiple repairs, earlier replacement is almost always the more economical path.
Repair vs. Replace: The Decision Framework
Repair is cost-effective when: damage is localized (one or two zones), the membrane is under 20 years old, and the deck is structurally sound. Replacement is more cost-effective when: the membrane is 25+ years old, multiple areas are failing, or deck damage is widespread. Cossette provides honest guidance on the right path during the free inspection.
Frequently Asked Questions
Does flat roof replacement include removing the old membrane in Cossette’s quote?
Yes. Cossette’s flat roof estimates include full tear-off of the existing membrane, disposal of materials, deck inspection, and complete installation of the new two-layer SBS system. No hidden fees.
Is flat roofing covered by Quebec home insurance?
Sudden storm or impact damage to a flat roof may be covered. Gradual deterioration or wear is not. If your flat roof fails following a specific weather event, document the damage immediately and notify your insurer. Cossette can provide a written damage assessment for insurance purposes.
Can Cossette add insulation to my flat roof in Gatineau?
Yes. Adding rigid insulation board as part of a flat roof replacement improves thermal performance significantly and is recommended when the existing insulation is damaged or inadequate. Cossette includes insulation assessment and pricing in flat roof estimates.