Blog
31 August 2026
Moisture marks on the ceiling, blisters on the flat roof or water infiltration after a heavy rain? These signs often mean the roof membrane is damaged. In Repentigny, as elsewhere in Quebec, a damaged membrane gradually lets water reach the insulation and the building structure. The longer you wait, the more the damage is likely to spread and the bigger the work becomes.
Whether you own a plex, an apartment building, a commercial property or a flat-roof house, it helps to know how to recognize the signs of a tired membrane and to understand how a repair is carried out.
On a flat roof, the membrane is the central waterproofing element. It forms a continuous barrier between the outside and the inside of the building. If it fails, rainwater, melting snow and moisture seep into the roof assembly and cause progressive damage that is often invisible at first.
Quebec's climate puts roofs to the test: freeze-thaw cycles, snow buildup, heavy spring rains and intense summer heat. A membrane that is properly installed and regularly maintained can protect a building for several decades. Without maintenance, however, it can deteriorate much sooner.
This is often the first sign that something is wrong. Brown stains or rings on the ceiling indicate that water is getting in somewhere. Several weeks can go by before the problem becomes visible inside, which means the membrane has sometimes been damaged for quite a while.
Bulging areas, blisters or membrane sections that lift show that adhesion is compromised. Moisture has probably worked its way under the membrane. These areas are fragile and need to be addressed quickly.
An aging membrane can develop cracks, especially in spots subject to movement or impact. Seams, upstands and the areas around penetrations (vents, ducts, mechanical units) are often the first to give way.
When roof drains are clogged with leaves or debris, water pools and eventually finds the slightest weak point in the membrane. Regular roof drain cleaning is one of the basic preventive measures.
Elastomeric membrane is very common on flat roofs in Quebec. It is made of SBS modified bitumen, a blend that keeps it flexible, even in cold weather, and gives it good resistance to temperature changes. It is installed as a two-ply system: a base sheet, then a granulated cap sheet that protects the whole assembly from UV rays.
Depending on the building and the chosen system, the membrane is torch-applied or installed as a self-adhered membrane. This is the type of roofing Toitures OBM specializes in, using Soprema systems.
You may be tempted to patch a leak yourself with a product from the hardware store. This approach rarely solves the problem: without finding the exact source of the water infiltration, you only mask the symptoms and the water keeps finding its way in.
The roofer inspects the entire roof: overall condition of the membrane, seams, upstands, penetrations, roof drains and water drainage. This overview pinpoints the cause of the problem and leads to the work that matches the actual condition of the roof.
The damaged area is cleaned and dried, loose or damaged sections are removed, then a new SBS modified bitumen membrane is installed overlapping the sound membrane. Around roof drains and penetrations, the waterproofing is carefully redone, since this is often where leaks start.
The answer depends on the overall condition of the membrane. If the damage is limited to one or two specific areas and the rest is in good condition, a targeted repair is often enough. If the membrane is sound but its surface is worn, resurfacing (cleaning, preparing the existing membrane and adding a new cap sheet) can extend its service life.
On the other hand, if the membrane has multiple separations or cracks, if the insulation is wet or if repairs keep piling up, a elastomeric roof replacement often becomes the most sensible long-term solution. Toitures OBM assesses the condition of the roof before recommending anything, to avoid unnecessary work.
Every season brings its own challenges. In winter, snow and freeze-thaw cycles stress the membrane. In spring, the melt reveals weaknesses that were previously invisible. In summer, UV rays wear down exposed materials. In fall, leaves clog the roof drains. Acting quickly helps protect the insulation, reduces the risk of mould and preserves the value of the building.
Toitures OBM is a roofer specializing in elastomeric membrane flat roofs, based at 1215 rue Tellier in Laval. Its service area stretches from Lachute to Repentigny and also includes Terrebonne, Mascouche, Laval and Montreal. The team offers flat roof repair, resurfacing, maintenance and inspection, elastomeric roof replacement and new flat roof construction, for commercial buildings, industrial and multi-unit buildings as well as residential flat roofs.
Toitures OBM is Soprema PAQ+S certified and CAA-Québec Recommended, and holds RBQ licence 5778-2823-01. Its recommendations are clear and explained. Financing is available through Financeit.
Yes, when the rest of the membrane is in good condition. The damaged section is removed, then a new membrane is installed overlapping the sound membrane. The inspection confirms that the problem is truly localized.
A membrane that feels spongy underfoot, soft spots or repeated leaks in the same place can indicate wet insulation. The roofer checks these areas during the inspection, since waterlogged insulation generally needs to be replaced.
One inspection in spring and another in fall make it possible to spot small issues and clean the roof drains before a problem gets worse.
At the first signs of water infiltration or deterioration, a diagnosis helps choose the right solution. 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.
