Blog
6 July 2026
A flat roof does not last forever. Over the years, the membrane wears out, the seams give way and water eventually finds its way in. When repairs keep adding up, a complete roof replacement often becomes the most durable solution.
Whether you own a flat-roofed home, an apartment building or a commercial building in Saint-Sauveur, here is what you need to know before undertaking a flat roof replacement.
Flat roof materials deteriorate over time. In Quebec, freeze-thaw cycles speed up this process: water seeps into small cracks, freezes, expands and widens the openings. Snow, the spring thaw and summer UV rays add to the wear.
A roof replacement becomes necessary when the membrane reaches the end of its life or when water has already reached the insulation. The age of the roof gives an indication, but it is its actual condition, as observed during the inspection, that determines the decision.
If several of these signs are present, an inspection will determine whether a repair or resurfacing is still enough, or whether a roof replacement is the most sensible solution.
Not every worn roof needs to be redone. When the damage is localized, a targeted repair may be enough. When the membrane is sound but its surface is worn, resurfacing (cleaning, preparation of the existing membrane and a cap sheet) can extend its service life.
A roof replacement becomes the right choice when the membrane has reached the end of its life across the entire roof, or when water has damaged the insulation. In that case, repeated repairs often just postpone the problem. Toitures OBM analyzes the condition of the roof and the needs of the building before recommending a roof replacement, to avoid unnecessary work.
It all starts with a complete inspection: condition of the membrane, insulation, roof deck, upstands and drainage system. These observations make it possible to define the scope of the work and the system to be installed.
In most roof replacements, the old membranes are removed, along with any damaged insulation. Installing a new membrane over wet or deteriorated materials would only postpone the problems. The roof deck is then checked before the work continues.
Once the surface is prepared, new insulation is installed as needed. This is often an opportunity to improve the building’s thermal comfort. Depending on the system selected, the insulation is mechanically fastened or adhered.
This is the heart of the job. The two-ply SBS modified bitumen system includes a base sheet and a cap sheet, torch-applied or self-adhered depending on the Soprema system chosen, for example a mechanically fastened conventional system or a self-adhered conventional system. The seams are carefully welded, and the upstands around the roof drains, penetrations and edges are redone.
Roof drains, flashings and edges receive special attention, since they are the spots most vulnerable to water infiltration. A check of water drainage completes the work.
An flat roof replacement done right protects the building against water infiltration, improves indoor comfort and reduces the risk of mould and structural deterioration. For an apartment building, it puts an end to repeated interventions that disturb tenants.
Acting in a planned way rather than reacting to damage is also more economical: interior damage caused by prolonged water infiltration adds to the cost of the roofing work.
The ideal time for a roof replacement is generally between spring and fall, when the weather allows quality work. An inspection done early in the season helps plan the work without rushing. For any question about permits, check with your municipality. Financing is available through Financeit.
Toitures OBM is a roofer 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, which includes Saint-Sauveur. The company carries out elastomeric roof replacements for commercial, industrial and multi-unit buildings, as well as for residential flat roofs.
Toitures OBM is Soprema PAQ+S certified, CAA-Québec Recommended and holds RBQ licence 5778-2823-01. Its recommendations are clear and explained, and its work methods are structured.
It depends on the condition of the roof. If the old membrane is sound and the insulation is dry, resurfacing may be considered. If the insulation is wet or the membrane is badly deteriorated, removing the old layers is generally necessary.
The duration depends on the surface area, roof access, the condition of the roof deck and the weather. The schedule is set after the inspection, once the scope of the work is known.
It can improve it when damaged insulation is replaced or insulation is added. Insulation options are discussed during the roof analysis.
Is your flat roof in Saint-Sauveur showing signs of wear? Contact Toitures OBM at 514-449-5469, Monday to Friday from 8 a.m. to 5 p.m., or request a free quote.
OBM Roofing
Elastomeric membrane specialists for commercial, industrial and multi-unit buildings in Laval, Montreal and the North Shore.
