Blog
11 May 2026
An elastomeric roof replacement involves replacing the covering of a flat roof with a new two-ply SBS modified bitumen system. In Laval, this work applies to apartment buildings and plexes as well as commercial and industrial buildings and flat-roof houses.
A roof replacement is a major project. Knowing how it unfolds, step by step, helps the owner plan it and understand what is being done on the roof. That is what this article describes.
An elastomeric roofing that is well maintained can last several decades, but it eventually reaches the end of its life. A roof replacement is generally considered when:
Toitures OBM assesses the condition of the roof before recommending anything. If a repair or resurfacing is enough, a roof replacement is not proposed. The goal is to avoid unnecessary work and to explain each recommendation clearly.
Waiting too long also has a cost for the building: an ongoing leak can soak the insulation, damage the roof deck and harm the top-floor ceilings. A roof replacement planned in time limits this damage.
Every roof is different, but a roof replacement follows a structured sequence.
The team examines the membrane, roof drains, upstands, penetrations and, if needed, the condition of the insulation. This assessment determines the scope of the work and the system to install. Toitures OBM works with Soprema systems, including the mechanically fastened conventional system and the self-adhered conventional system.
Before work begins, access, the container location and protection around the building are planned. For an occupied building, this lets the owner inform tenants of the work schedule.
The old membrane is removed, in whole or in part depending on the assessment. In general, the roof is opened in sections so that each section can be closed the same day.
Once the roof is exposed, the substrate and insulation are checked. Wet or crushed insulation is replaced, since it would compromise the new membrane. If the roof deck has a problem, the owner is informed before going any further. Areas of the roof deck that have been exposed to water for a long time deserve particular attention.
The elastomeric base sheet is installed on the prepared substrate, torch-applied or self-adhered depending on the chosen system. The rolls overlap to form a first watertight surface.
The roof drains are connected to the membrane, the upstands are redone along parapets and walls, and every penetration (vents, ducts, equipment bases) is sealed. These are the spots where most leaks occur, which is why they get so much care.
The granulated cap sheet covers the base sheet. Its granules protect the bitumen from UV rays and wear. Its seams are offset from those of the base sheet to strengthen watertightness.
Debris is picked up, the roof drains are checked and the roof is inspected one last time before the project wraps up. The owner is informed of what was done and what to keep an eye on.
Membrane work is done in dry conditions. In Quebec, the period from spring to fall is the most suitable, and the schedule often fills up early. Having the roof assessed at the first signs of wear leaves time to plan the work at the right moment, rather than having to deal with it after a leak.
For permits, check with your municipality depending on the nature of the work. Toitures OBM also offers financing through Financeit for owners who want to spread out the cost.
A new roof also needs maintenance. An inspection in spring and fall is a chance to check the roof drains and water drainage, seams, upstands, penetrations and the overall condition of the membrane, along with cleaning the roof drains. This maintenance helps the new membrane last several decades.
Toitures OBM is a roofer specializing in elastomeric membrane flat roofs, based at 1215 rue Tellier in Laval. Laval and Montreal are its main markets, and the company also works on the North Shore. Its services include elastomeric roof replacement, new flat roof construction, repair, resurfacing, and maintenance and inspection.
Toitures OBM is Soprema PAQ+S certified, CAA-Québec Recommended and holds RBQ licence 5778-2823-01.
It depends on the roof area, the number of penetrations, the condition of the insulation and the weather. The expected duration is specified after the roof assessment.
In most cases, the old roofing is removed to check the substrate and insulation. The assessment shows what is right for your roof.
In general, the roof is opened in sections and each section is closed before the end of the day. Membrane work is postponed when rain is forecast.
To have your elastomeric roof assessed and plan a roof replacement, contact the Toitures OBM team Monday to Friday, from 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.
