Flat Roof Options
Since no roofing system is suitable for all buildings and all needs, it is advisable to hire an expert to evaluate all the issues. The list below summarizes the major recognized systems available and proven in Quebec.
See also below our COMPARATIVE TABLE of major conventional flat roof systems.
TPO (thermoplastic polyolefin)
Typically a white membrane, delivered in 5 to 12 feet (3.66 meters) wide rolls and polyester reinforced, which allows it to be mechanically secured to the roof at a low cost. Durable, attractive and very reflective, it is more and more popular for basin-type roofs and very low slope roofs. Its junctions are welded with very hot air.
SBS modified bitumen
Bitumen membrane modified with polymers to improve its properties. Reliable, attractive and very popular in Canada. The granulated finish available in a wide color palette serves to protect bitumen against UV rays. Installed in two layers which are fused with torches, the first layer is glued or mechanically fixed to the roof.
EPDM (synthetic rubber)
Black or white membrane known for its unmatched durability in the industry. However, glued joints require great care to last as long as the membrane itself. The white version must be completely glued, while the black can also be ballasted. The black reinforced version can be either mechanically fixed or glued.
Asphalt and gravel (built-up roof)
Conventional coating consisting of multiple layers of roof felts laminated together with bitumen. A final layer of gravel is spread on the surface to protect the bitumen from the sun, sudden temperature changes and hail impacts. This system is now seldom used on large surfaces and is losing popularity since some municipal by-laws even prohibit its installation.
Coatings and other flat roofing systems
Polymers, bitumen, silicone, acrylic, liquid rubber, fiberglass, polyurea, etc. Many products are offered on the market but very few are thoroughly tested and standardized by the industry. Few specialized labor and installation standards brings the risk of losing local expertise by using a method which is too marginal.
Comparative table of major flat roofing options
This table shows an overall view presented for information purposes only. Endless variables can substantially modify the information it contains, use with caution and discernment.
| ROOFING TYPE | AVERAGE PRODUCT LIFE (1) | ANNUAL COST (2) | PURCHASE PRICE (2) | RELIABILITY (3) | VERSATILITY (4) | REFLECTIVITY (5) | ENVIRONMENTALLY FRIENDLY (6) |
| TPO Membrane | good | very low | low | average | good | very good | very good |
| Modified bitumen membrane (elastomer) | good | average | high | reliable | very good | average | low |
| EPDM Membrane | good (1) | low | high | average | good | good | good |
| Built-up roof (asphalt and gravel) | low | high | low | very reliable | low | low | very low |
| PVC Membrane | good | low | average | average | good | very good | low |
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Product life is not only based on the sustainability of the material itself but also on its seams, for example EPDM membrane itself is very durable but its glued joints last often less than with other systems..
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Cost classification is based on a small area (less than 200 square meters or 2000 square feet). Beyond that, mechanically attached systems become more and more economical, even compared to ballasted systems.
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Reliability includes resistance to fire, impacts, punctures, tears and natural elements.
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Versatility considers ease of installation in all circumstances and the ease of modification and repair.
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Reflectivity depends largely on the effectiveness of the system to self-clean.
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CClassification of the ecological value of a system is not only based on its recyclability since some materials are recyclable but not recycled, such as elastomer in Quebec. This value is greatly affected by sustainability but also by the amount of energy required in the material’s life cycle.