Modified Bitumen vs TPO: Choosing a Commercial Flat Roof in Ontario
How a layered, asphalt-based roof compares with a single white, heat-welded sheet on foot traffic, summer heat, cold-weather installs, lifespan and cost.
Call 1-833-775-7663 Oakville head office · Modified bitumen and TPO roofs for commercial, industrial and institutional buildings across Ontario
Karol Rajkowski
Vice President, OYH Roofing
Published October 6, 2026 · 9 min read
Short answer
Modified bitumen vs TPO comes down to traffic, heat and budget. Modified bitumen is an asphalt-based roof built in two or more plies, so it stands up to foot traffic and service crews. TPO is one white, heat-welded sheet that reflects summer heat and usually costs less to install. Both are proven on Ontario commercial roofs.
What is the difference between modified bitumen and TPO?
The main difference in modified bitumen vs TPO is how the roof is built. Modified bitumen is asphalt blended with a rubber-like SBS or a plastic APP polymer and installed in two or three plies, a base sheet and a granulated cap sheet. TPO is a single thermoplastic sheet whose seams are welded with hot air.
| Difference | Modified bitumen | TPO |
|---|---|---|
| Material | Asphalt modified with SBS rubber or APP plastic, reinforced with polyester or glass | Thermoplastic polyolefin sheet with a polyester or glass reinforcement |
| Layers | Two or three plies: a base sheet plus a granulated cap sheet | One ply, 45, 60 or 80 mil thick |
| Installation | Torch, hot asphalt, cold adhesive or self-adhered | Mechanically attached, fully adhered or induction-welded; seams welded with hot air |
| Surface and summer heat | Granulated cap sheet; reflective cap sheets rated by the Cool Roof Rating Council are available | White; IKO rates its Innovi TPO at SRI 97 new and 90 after three years |
| Foot traffic and punctures | Several plies that ARMA says are difficult to pierce or puncture | One sheet; a thicker membrane and walkway pads protect it |
| Lifespan (makers' figures) | 25 to 30 years for the SBS membranes in a SOPREMA case study; 10 to 30 years (GAF blog) | 20 to 30 years for a high-quality system (Holcim Elevate) |
| Installed cost | Usually higher than TPO | Usually lower, according to Holcim Elevate |
Both systems are proven, so the modified bitumen vs TPO decision depends on the roof, not the label. For other pairings, see our TPO vs EPDM guide and our PVC vs TPO guide, and our commercial flat roof lifespan guide covers how long each system lasts.
When is modified bitumen the better choice?
Modified bitumen is usually the better choice in the modified bitumen vs TPO decision when the roof takes a beating: regular foot traffic from service crews, many rooftop units, or exposure to hail and windblown debris.
- A second layer of protection. GAF notes that commercial asphalt roofs have two or more waterproofing layers, and ARMA says the numerous layers are difficult to pierce or puncture. If the cap sheet is damaged, the base sheet is still there.
- Storms and debris. IKO says the granular surface holds up well to heavy precipitation and wind, and that the membrane's puncture and tear resistance prevents damage from blowing debris.
- Movement and temperature swings. ARMA credits SBS with superior elongation and recovery across a wide range of low and high temperatures.
- A choice of installation. SBS sheets can be torched, mopped with hot asphalt, set in cold adhesive or self-adhered, so the method can suit the building.
The weak points: torch-applied sheets need an open flame, which IKO calls a fire risk that takes skill to manage; laps fail when they are not fully sealed; and grease softens asphalt-based roofs. ARMA notes that low-odour cold adhesives let occupied buildings such as schools, hospitals and offices be re-roofed without open flames or hot kettles.
When is TPO the better choice?
TPO is usually the better choice in the modified bitumen vs TPO decision when the roof is large and plain, the building is air-conditioned and the budget matters.
- Summer heat. White TPO reflects sunlight. IKO rates its white Innovi TPO at a Solar Reflectance Index of 97 when new and 90 after three years.
- Toronto's cool roof grant. The Eco-Roof Incentive Program pays $5 per square metre, up to $50,000, for a new cool roof membrane with an SRI of 78 or more on a low-slope roof, and the city must approve the application before work starts. For a modified bitumen cap sheet, ask for its rated SRI; GAF sells reflective cap sheets rated by the Cool Roof Rating Council.
- No open flame. TPO seams are welded with hot air, which suits occupied buildings.
- Lower installed cost. Holcim Elevate says its TPO membranes have lower installed costs than other commercial roofing materials.
The weak points: with one ply, a puncture goes straight through to the insulation, the welds depend on the installer, and old TPO needs careful cleaning before a repair will weld. Walkway pads to every unit and a thicker membrane help on busy roofs. Our cool roof guide explains the Toronto grant.
Weighing modified bitumen vs TPO?
Tell us how the roof is used, and we will set up a free roof assessment and price both systems on the same specification.
Call 1-833-775-7663Request an assessmentWhich one fits your roof?
Match the system to how the roof is used. In the TPO vs modified bitumen choice, traffic, heat, grease and the way the work has to be done on site usually decide it.
| Your roof | Usually the better fit | Why |
|---|---|---|
| Heavy foot traffic, many rooftop units | Modified bitumen | Two or more plies are difficult to puncture |
| Large, plain roof on an air-conditioned building | TPO | White surface keeps summer heat out, at a lower installed cost |
| Applying for Toronto's cool roof grant | TPO, or a cap sheet rated SRI 78 or more | The grant requires SRI 78 or more on a low-slope roof |
| Occupied building where a torch is a concern | TPO, or cold-applied or self-adhered modified bitumen | Hot-air welding and cold adhesives avoid an open flame |
| Hail and windblown debris | Modified bitumen | Granulated surface with puncture and tear resistance |
| Kitchen exhaust with grease | Neither by default | Grease softens asphalt; pick a membrane its maker rates for grease |
Grease is its own case, and our restaurant roofing guide covers it in detail.
How do they handle Ontario winters and cold-weather installs?
Once installed, both systems are used on roofs across Ontario. In winter, the bigger modified bitumen vs TPO difference is installation in the cold, where each method has its own temperature limits.
In service, SBS keeps its elongation and recovery across low and high temperatures, according to ARMA, and TPO's welded seams join the sheets into one piece. The limits below apply while the roof is going on:
| Installation step | System | Cold-weather limit (example) |
|---|---|---|
| Membrane adhesive, standard | TPO | 4°C (IKO) |
| Membrane adhesive, cold-weather version | TPO | -4°C (IKO) |
| Primer and sealant | TPO | -7°C (IKO) |
| Self-adhered sheets | Modified bitumen | Typically 4 to 10°C (ARMA) |
| Cold adhesive | Modified bitumen | Best from 10 to 38°C; colder only with precautions (ARMA) |
| Storing rolls on site | Modified bitumen | Heated storage below 10°C (ARMA) |
Toronto's average daily temperature is 4.1°C in November and below freezing from December to February, in Environment Canada's 1991 to 2020 normals, so many of these steps wait for a warmer day once winter sets in. Our guide on how to prepare a flat roof for winter explains the fall window.
What modified bitumen and TPO roofs has OYH Roofing installed?
OYH Roofing installs both systems on commercial, industrial and institutional buildings. Our published projects show both sides of modified bitumen vs TPO: four modified bitumen roofs and two TPO roofs.
| Project | System | Size | Warranty |
|---|---|---|---|
| 777 Niagara St, Welland | IKO 2-ply modified bitumen | 52,300 sq ft | 20-year system warranty |
| City of Mississauga, 3185 Mavis Rd | IKO 2-ply modified bitumen | 8,500 sq ft | 20-year system warranty |
| Industrial building, Mississauga | 2-ply modified bitumen | 53,000 sq ft | 20 years on labour and materials |
| Marriott Hotel, Vaughan (new build) | 2-ply modified bitumen | 15,000 sq ft | 20 years on labour and materials |
| Millomat Stampings, Mississauga | 60 mil TPO | 50,000 sq ft | 20 years on labour and materials |
| Devi Mandir, Pickering | 60 mil TPO | 6,500 sq ft | 20 years on labour and materials |
See the rest on the completed projects page, or read about our roofing services.
Can you switch from modified bitumen to TPO?
Yes. A roof can move from modified bitumen to TPO at replacement time, either with a full tear-off or, in some cases, a recover over the old roof. A recover only works when the old roof is dry and the TPO maker approves the build-up, usually with a cover board in between.
At Devi Mandir in Pickering, two old modified bitumen layers and a coating came off before the new 60 mil TPO roof went on. Some makers also sell hybrid roofs: GAF says combining SBS modified bitumen and TPO can increase the overall robustness of the assembly. Our warehouse roof replacement guide explains how owners choose between a recover and a tear-off.
Frequently asked questions
Is TPO better than modified bitumen?
Not across the board. In TPO vs modified bitumen, TPO is usually better for large, plain roofs on air-conditioned buildings, because it is white, heat-welded and cheaper to install. Modified bitumen is usually better where crews walk the roof often or debris is a risk, because its two or more plies are hard to puncture. How the roof is used decides it.
Is TPO more expensive than modified bitumen?
Usually not. Holcim Elevate, which makes TPO, says its TPO membranes have lower installed costs than other commercial roofing materials, and a two-ply modified bitumen roof puts down two layers instead of one. The real gap depends on insulation, details and access, so compare both systems priced on the same specification.
What are the common problems with modified bitumen roofing?
The usual problems are laps and seams that were not fully sealed, blisters and cracks in the plies, worn paths where crews walk, and damage from grease or oils. IKO notes that seam failures and installation errors can cause leaks, which is why good details and inspections twice a year matter.
How long will a modified bitumen roof last?
A well-installed modified bitumen roof usually lasts 20 to 30 years. SOPREMA puts the SBS membranes in one of its case studies at 25 to 30 years, and a January 2026 GAF blog lists 10 to 30 years for SBS. OYH's 2-ply modified bitumen roofs carry 20-year warranties, either a system warranty or one on labour and materials.
What are the two main types of modified bitumen roofing?
The two main types are SBS and APP. SBS uses a rubber-like polymer that keeps the sheet flexible, with strong elongation and recovery across low and high temperatures, and it can be torched, mopped, glued or self-adhered. APP uses a plastic polymer that improves resistance to high temperatures and UV light, and it melts at a higher temperature than SBS.
What is the best type of roof for a commercial building?
There is no single best type. On Ontario commercial roofs, modified bitumen, TPO, PVC, EPDM and built-up roofing all have a place: modified bitumen for traffic and toughness, TPO and PVC for welded seams and reflective surfaces, EPDM for flexibility. The best roof suits the building's use, budget and exposure, and is installed and inspected well.
Karol Rajkowski
Vice President · OYH Roofing
Karol Rajkowski is Vice President of OYH Roofing, an Oakville-based ICI flat-roofing contractor whose projects include the City of Mississauga building at 3185 Mavis Rd and the Marriott Hotel in Vaughan. Learn more about the OYH team.
Sources
- Guide to Torch Down Roofing, IKO Commercial.
- Key Facts to Know About TPO Commercial Roofing, IKO Commercial.
- Protecting Your Commercial Roof from Storm Damage, IKO Commercial.
- IKO Innovi TPO Roofing Systems: Cold Weather Guidelines, IKO Commercial bulletin MM3L006-32, December 2025.
- Built to Last: Multilayer Asphalt Roofing Stands Up to Weather Extremes, Asphalt Roofing Manufacturers Association, April 30, 2018.
- Cold Adhesive SBS-Modified Bitumen Roofing Applications, Asphalt Roofing Manufacturers Association, May 12, 2015.
- Cold Weather Application Recommendations for Modified Bitumen Roofing, Asphalt Roofing Manufacturers Association technical bulletin, revised April 2024.
- Commercial Modified Bitumen Roofing Systems, GAF.
- What Is the Lifespan of a Commercial Roof?, GAF RoofViews blog, January 20, 2026.
- The EPDM vs. TPO debate, Holcim Elevate.
- What is the Difference Between PVC & TPO Roofing?, Holcim Elevate.
- Increasing the Durability of a Roofing System Through Resurfacing, SOPREMA, August 24, 2020.
- Eco-Roof Incentive Program, City of Toronto.
- Canadian Climate Normals 1991 to 2020: Toronto Pearson (Airport), Environment and Climate Change Canada.
- Maintaining compliance, Professional Roofing (NRCA), February 2024.
- OYH Roofing project records: 777 Niagara St, Welland; City of Mississauga, 3185 Mavis Rd; industrial building, Mississauga; Marriott Hotel, Vaughan; Millomat Stampings, Mississauga; Devi Mandir, Pickering (October 2026).
OYH Roofing, 2120 Speers Rd, Oakville, ON L6L 2X8 · 1-833-775-7663 · info@oyhroofing.ca