Blog
30 March 2026
In Laval, apartment buildings, plexes, and commercial and industrial buildings very often have a flat roof. On this type of roof, the elastomeric membrane is a very common solution in Quebec: a two-ply SBS modified bitumen system that forms a continuous, flexible and watertight covering.
Here is how an elastomeric roof works, what makes it well suited to flat roofs in Laval, which service to choose based on the condition of your roof and how to maintain it so it lasts a long time.
The term "elastomeric" refers here to an SBS (styrene-butadiene-styrene) modified bitumen membrane. This polymer gives the bitumen an elasticity it does not have in its natural state: the membrane can stretch and return to its shape without cracking, even in cold weather.
On a flat roof, the system is almost always two-ply:
The membranes can be torch-applied or self-adhered, depending on the building, the substrate and the constraints of the job site. Toitures OBM works with Soprema systems, such as the mechanically fastened conventional system or the self-adhered conventional system.
On a flat roof, water drains slowly toward the roof drains, snow builds up in winter and the surface is directly exposed to the sun in summer. The membrane must therefore stay watertight over its entire surface, in every season.
Quebec’s climate takes the roof from intense cold to summer heat, with many freeze-thaw cycles in the spring and fall. The building moves slightly with these temperature swings. Thanks to SBS, the membrane follows these movements instead of cracking, which reduces the risk of water infiltration.
The membrane rolls overlap and are welded together. Once both layers are installed, the roof forms a single watertight surface. The vulnerable spots remain the roof drains, the upstands along the parapets and the penetrations (vents, ducts, mechanical equipment bases), which require careful workmanship.
Over time, the sun degrades bitumen. The granules on the cap sheet act as a shield: they protect the membrane and help it stay flexible longer. Visible granule loss is, in fact, one of the signs to watch for during an inspection.
Not all elastomeric roofs need the same work. Toitures OBM’s approach is to analyze the condition of the roof and the needs of the building before recommending anything, to avoid unnecessary work.
When the problem is localized, a repair is often enough: a leak in a specific spot, resealing around a roof drain or a penetration, a crack or a delaminated section. The work targets the cause of the leak, not just the stain on the ceiling.
If the membrane is ageing but still sound overall, resurfacing can extend its service life. It includes cleaning, preparing the existing membrane and applying a cap sheet.
When problems multiply or the membrane reaches the end of its life, a roof replacement replaces the roofing with a new two-ply system. It is also an opportunity to properly redo the waterproofing details around the roof drains, upstands and penetrations.
For a new building or an addition, Toitures OBM installs the complete elastomeric flat roof, according to the system chosen for the project.
A properly installed elastomeric membrane can last several decades with regular maintenance. On the other hand, a clogged roof drain or a damaged upstand that is left unattended can cause damage well before the membrane reaches the end of its life.
An roof inspection checks, among other things:
One visit in the spring, after the thaw, and another in the fall, before winter, make it possible to spot small problems while they are still simple to fix.
Toitures OBM is a roofer specialized in elastomeric membrane flat roofs, located at 1215 Tellier Street in Laval. The company works on commercial, industrial and multi-unit buildings, as well as on residential flat roofs, throughout Laval and Montreal, its main markets, and on the North Shore.
Toitures OBM is Soprema PAQ+S certified, CAA-Québec Recommended and holds RBQ licence 5778-2823-01. Each recommendation is clearly explained to the owner, and the work follows structured methods. Financing is also available through Financeit.
Yes. The two-ply elastomeric membrane is used on plexes and apartment buildings as much as on commercial buildings. The choice between a torch-applied or self-adhered installation depends on the substrate and the constraints of the building.
An inspection can determine this. An isolated problem is often solved with a repair; a membrane worn over a large area calls instead for resurfacing or a roof replacement.
Requirements vary depending on the nature of the work. Check with your municipality before the work begins.
For an inspection, a repair or a complete roof replacement, the Toitures OBM team can be reached Monday to Friday, from 8 a.m. to 5 p.m. Call 514-449-5469 or request a free quote for your elastomeric roof in Laval.
OBM Roofing
Elastomeric membrane specialists for commercial, industrial and multi-unit buildings in Laval, Montreal and the North Shore.
