Elastomeric Membrane Roof Cost in Montreal

Elastomeric membrane roofing consists of two layers: a base sheet and a cap sheet, both made of SBS (styrene-butadiene-styrene) modified bitumen. The SBS modifier gives the membrane rubber-like elasticity, allowing it to expand and contract with temperature changes without cracking or splitting. This property makes it particularly well-suited to Quebec's climate, where temperature swings between summer and winter can exceed 60 degrees Celsius. The cost of an elastomeric membrane installation depends on roof size, the condition of the existing roof, the number of details and penetrations, and whether additional insulation or slope correction is required. The two-layer system is applied by torch, with each layer heated and adhered to the substrate. Proper torch application requires experienced installers who understand how to achieve full adhesion without overheating the membrane. Existing roof condition is a major cost factor. If the current membrane is in poor condition with multiple patches, ponding areas, or blistering, a full tear-off is typically recommended. If the existing membrane is in reasonable condition, a re-cover may be possible, where new membrane is installed directly over the old. This saves the cost of tear-off and disposal but adds weight to the roof structure. Insulation can be incorporated into the membrane system using rigid insulation boards installed above the roof deck and below the membrane. This approach improves the building's thermal performance and can help create the slope needed for proper drainage. Parapet walls, drains, scuppers, plumbing vents, HVAC penetrations, and skylights all require careful detailing that adds to the project scope. Each detail is a potential failure point if not properly executed. Based on Quebec market data for 2025-2026, here are the typical costs for elastomeric membrane roofing in Montreal: The material cost for elastomeric membrane is approximately $4 to $8 per square foot (Soumissions Toiture, 2025). With installation, the total cost of an elastomeric membrane roof typically ranges from $9 to $20 per square foot, depending on project complexity and whether the existing roof needs to be torn off (Soumissions Quebec, 2026). For a typical flat roof of 1,000 square feet, an elastomeric membrane installation costs between $10,000 and $20,000 (Soumission Renovation, 2026). Larger projects on multi-unit residential buildings commonly fall in the $16,000 to $30,000 range (Soumissions Quebec). A re-cover installation, where new membrane is applied over an existing membrane in reasonable condition, costs less than a full tear-off and replacement. However, the building code limits the total number of layers, and the existing membrane must be evaluated to determine whether a re-cover is feasible. Elastomeric membrane has a proven lifespan of 25 to 40 years in Quebec conditions (Soumissions Toiture), making it one of the most durable flat roof options available. The two-layer system provides redundant waterproofing protection, which is particularly valuable in a climate with extreme temperature swings. Adding rigid insulation beneath the membrane increases the project cost but improves energy efficiency and can help create proper drainage slope. With current energy prices in Quebec, the insulation investment typically pays for itself within a few years through reduced heating costs. Contact us for a free flat roof assessment. We inspect your existing system and recommend the most cost-effective approach.