Blog
23 March 2026
In Sainte-Adèle, commercial buildings, apartment buildings and flat-roofed houses all have one thing in common: their roof must stay watertight despite the snow, rain, sun and freeze-thaw cycles of the Quebec climate. An elastomeric flat roof, made of SBS modified bitumen membranes, is designed for these conditions.
This article explains why this membrane is suited to flat roofs, why it is installed in two plies and which factors have the greatest influence on its lifespan.
A flat roof is never completely flat: it has a slight slope that directs water toward the roof drains. However, water moves slowly across it, and snow can stay on it for several weeks. The membrane must therefore form a continuous surface, without weak spots, able to stay watertight under water and snow.
Bitumen on its own becomes stiff and brittle in the cold. By adding SBS (styrene-butadiene-styrene), an elastic polymer, you get a membrane that stays flexible even in winter. It can follow the building’s expansion and contraction without cracking. That is what earns it the name elastomeric membrane.
The membrane is reinforced with polyester or fibreglass, which gives it its tear resistance and stability during installation.
This flexibility is useful during the spring and fall freeze-thaw cycles, when the temperature goes above and below zero several times in a short period. A rigid membrane would have a much harder time withstanding these repeated movements.
On a flat roof, the elastomeric membrane is installed as a two-ply system:
The seams of the cap sheet are staggered in relation to those of the base sheet. If a surface seam were to fail, the base sheet would continue to keep the water out. This redundancy reduces the risk of leaks.
The membranes can be torch-applied or self-adhered. Toitures OBM works with Soprema systems, such as the conventional mechanically fastened system or the conventional self-adhered system, chosen according to the building and the substrate.
With regular maintenance, an elastomeric flat roof can last several decades. However, several factors make the difference between a membrane that ages well and one that causes problems early on.
A weld that is too cold does not bond properly; a weld that is too hot damages the membrane. A damp or poorly prepared substrate can cause blisters. Installation therefore requires experience and a structured work method.
Where water pools after rain, the membrane ages faster. Roof drains that are well placed, properly connected and kept clear allow water to leave the roof quickly.
The upstands along parapets and walls, as well as penetrations (vents, ducts, equipment bases), are the areas most exposed to leaks. Their execution matters as much as the installation of the membrane itself.
UV rays degrade bitumen over the years. The granules on the cap sheet act as a shield. When they come off in large quantities, the membrane becomes more vulnerable.
An inspection in spring and fall makes it possible to check the roof drains and water drainage, the seams, the upstands, the penetrations and the general condition of the membrane, and to clean the roof drains. A small problem caught early can often be fixed with a simple repair. Conversely, a clogged roof drain or a loose upstand that is left unattended can soak the insulation and cause damage well before the membrane reaches the end of its life.
An elastomeric flat roof is suitable for commercial and industrial buildings, apartment buildings and plexes, as well as flat-roofed houses. For a new building, Toitures OBM carries out new flat roof construction. For an existing roof, the company offers repair, resurfacing, elastomeric roof replacement as well as maintenance and inspection.
In every case, the condition of the roof and the needs of the building are assessed before any recommendation is made, to avoid unnecessary work.
Toitures OBM is a roofing contractor specializing in elastomeric membrane flat roofs, located at 1215 Tellier Street in Laval. Its service area extends from Sainte-Adèle to Montreal, and from Lachute to Repentigny. Property owners in Sainte-Adèle can therefore call on the team for their flat roof.
Toitures OBM is Soprema PAQ+S certified, CAA-Québec Recommended and holds RBQ licence 5778-2823-01. Financing is available through Financeit.
The base sheet and the cap sheet form two watertight barriers whose seams are not aligned. This layering reduces the risk of leaks and better protects the roof against wear.
They protect the bitumen from UV rays and wear. Significant granule loss is a sign that the membrane is aging and should be inspected.
Yes. The same type of two-ply system is installed on flat-roofed houses as well as on commercial buildings and apartment buildings.
To have your elastomeric flat roof in Sainte-Adèle assessed, contact the Toitures OBM team Monday to Friday, 8 a.m. to 5 p.m., at 514-449-5469, or request a free quote.
OBM Roofing
Elastomeric membrane specialists for commercial, industrial and multi-unit buildings in Laval, Montreal and the North Shore.
