Commercial Roof Membranes

Two main families

Bituminous systems go down in several layers. Modified bitumen, also called elastomeric membrane, has a base sheet and a cap sheet covered in granules. Tar and gravel, or built-up roofing, stacks several felts set in hot asphalt, protected by gravel.

Single-ply membranes are one sheet. TPO is a thermoplastic membrane, often white, with seams welded with hot air. EPDM is a synthetic rubber membrane delivered in large sheets, with glued seams. PVC is another thermoplastic single-ply membrane, also welded with hot air.

The chosen system sets the weight added to the building, the installation method and the maintenance for decades to come.

The criteria that really matter

We do not propose a system out of habit. We look at the building.

• The structure. A light steel deck does not take the same loads as a concrete slab. A heavy or ballasted system calls for a structural engineer's opinion.
• Foot traffic. The more often technicians go up on the roof, the more the membrane must resist punctures.
• What the building releases. Grease from a restaurant kitchen and some industrial products attack certain membranes more than others.
• Penetrations. A roof covered in equipment needs a lot of detail work.
• Reflectance. Several boroughs require a white roof or a reflective material when a roof is replaced. Colour then becomes an eligibility criterion.
• The installation method. Torch, hot asphalt, adhesive, mechanical fastening and hot-air welding do not affect occupants the same way.

Lifespans as orders of magnitude

Depending on the manufacturer and the quality of installation, an elastomeric membrane lasts 25 to 35 years, a tar and gravel roof 15 to 25 years, and a TPO or EPDM membrane 20 to 30 years.

These figures assume a roof that drains well, with careful details and regular maintenance.

The system is more than the membrane

Under the membrane are a vapour barrier, insulation, often a cover board, and a way of attaching it all to the deck. These layers decide wind resistance, thermal performance and long-term durability.

Two quotes for "a TPO roof" can describe two very different roofs. To compare them, check that each quote states:

1. The full assembly, from the deck to the surface.
2. How the insulation and the membrane are attached.
3. The thickness of the membrane and of the insulation.
4. How parapets, drains and equipment are handled.
5. The warranties offered, by whom, and under what maintenance conditions.

Keeping the same system or changing it

Redoing the roof with the same system as before is often the simplest path. The structure already carries that system and the details are known. Switching families makes sense when the building's use has changed, when the borough requires a reflective surface, or when the old system aged badly for a specific reason.

Frequently asked questions