TPO vs EPDM vs Torch On — The BC Flat Roof Guide

Three systems cover the vast majority of flat and low slope roofs across Metro Vancouver: TPO, EPDM, and torch on SBS. Each has a place, and the right answer depends on your building, your budget, and how long you plan to hold the property. Here is the honest comparison from a crew that installs all three. From Paragon Roofing BC, family owned since 2010.

If you have a flat or low slope roof in the Lower Mainland, you will almost always be choosing between three systems. Torch on SBS is a two ply modified bitumen membrane that gets heat welded in place. TPO is a single ply thermoplastic sheet that is hot air welded at the seams. EPDM is a single ply rubber membrane, typically glued or mechanically fastened with taped or glued seams. All three can give you a long lasting, watertight roof when they are installed correctly. The differences are in cost, repairability, how they handle our climate, and what suits your specific deck.

There is no single winner. A small residential low slope section behind a dormer is a different problem than a 20,000 square foot strata podium or a warehouse. Below we break down where each system earns its place, then give you a side by side table and a plain verdict for the common situations we see.

Torch on SBS: the residential workhorse

Torch on remains the most common low slope system on Lower Mainland houses, and for good reason. The two ply build gives you genuine redundancy, the granulated cap sheet stands up well to foot traffic and UV, and detailing around penetrations, drains, and walls is straightforward for an experienced crew. It handles our wet winters and the freeze thaw cycles at higher elevations very well. The trade off is that it is a hot work process, so it needs a skilled crew and sensible fire safety, and the dark cap sheet absorbs heat rather than reflecting it. For most residential flat sections, rooftop decks over living space, and additions, torch on is still our default recommendation.

TPO: the reflective single ply

TPO is a single ply sheet that comes in wide rolls and is hot air welded at the seams. Its biggest advantage is the white reflective surface, which keeps the roof and the space below cooler in summer and is the reason it dominates commercial and strata flat roofs. It installs quickly over large open areas, which keeps labour reasonable on big decks. The things to watch are that it is a single layer rather than two, so a puncture matters more, and weld quality is everything. On a large strata or commercial flat roof, TPO is often the most sensible balance of cost, reflectivity, and speed.

EPDM: the proven rubber

EPDM is a rubber membrane with a long track record, often the better part of half a century in the field. It is forgiving in cold weather, stays flexible, and is easy to patch, which makes it attractive for roofs that will see future modification or rooftop equipment. The classic black EPDM does not reflect heat the way TPO does, though lighter options exist. Seams are the historical weak point, so taped and properly rolled or glued seams done by a careful crew are essential. EPDM is a strong choice where flexibility, easy future repair, and long service life matter more than summer reflectivity.

Side by side comparison

Which one is right for you

Whatever the system, the install quality matters far more than the brand on the box. Seam welds, flashing details at walls and penetrations, drain integration, and proper slope to drain are where flat roofs succeed or fail. We install all three with our own in house crew, so the recommendation you get is based on your roof rather than on what we happen to stock. For more on our flat roof work, see our flat roofing services and commercial roofing pages.

Frequently Asked Questions

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