The short answer
A TPO roof is a single layer of thermoplastic polyolefin membrane, usually white, laid over insulation on a low-slope roof and joined at the seams with hot air. It is the most common membrane on new commercial roofs, typically costs $4 to $14 per square foot installed and lasts 20 to 30 years.
On this page
If you look down from a plane over any American business park, most of the bright white roofs you see are TPO. It has become the default membrane for warehouses, big box stores, offices and schools since the early 2000s, so if you manage a commercial building built or reroofed in the last twenty years, there is a good chance you have one.
What TPO is made of
TPO stands for thermoplastic polyolefin. It is a blend of polypropylene and ethylene-propylene rubber, made into sheets with a polyester reinforcing scrim in the middle. “Thermoplastic” is the important word: heat softens it, and when two softened sheets are pressed together they fuse into one. That is how the seams are made, and how most repairs are made too.
Sheets come in rolls, commonly 45, 60 or 80 mils thick (a mil is a thousandth of an inch), in white, gray or tan. White is by far the most common.
How a TPO roof is installed
A TPO roof is a system, not just a sheet. From the deck up, it usually has:
- Insulation boards, often polyiso, fastened or glued to the steel, wood or concrete deck, sometimes tapered to push water toward drains.
- A cover board on many roofs, which protects the insulation from foot traffic and hail.
- The TPO membrane, attached in one of three ways: mechanically fastened with plates and screws along the seams, fully adhered with bonding adhesive, or (less often) held down by ballast.
- Flashings in TPO at every wall, curb, drain and pipe, and metal edges at the perimeter.
The installer overlaps each sheet by a few inches and runs a robotic hot-air welder along the lap. A properly welded seam is stronger than the sheet itself. Under the International Building Code, the roof assembly also has to meet wind uplift and fire classifications, which is why manufacturers test complete systems rather than just the membrane.
How long does a TPO roof last?
Published guides put TPO at 20 to 30 years. Where a roof lands in that range depends on:
| Factor | Longer life | Shorter life |
|---|---|---|
| Thickness | 60 or 80 mil | 45 mil |
| Seams | Probed and tested at install | Under-welded or rushed |
| Traffic | Walkway pads to rooftop units | Service crews walking anywhere |
| Drainage | Water clears within two days | Ponding against seams |
| Maintenance | Inspected spring and fall | Only looked at when it leaks |
What TPO costs
National cost guides published in January 2026 put a new TPO roof at roughly $4 to $14 per square foot installed, with removing an old roof adding about $1 to $5 per square foot. Repairs are usually a few hundred dollars to about $1,100 a visit. Our repair cost estimator compares repair, coating and replacement for your roof size.
TPO vs EPDM vs PVC
All three are single-ply membranes, but they behave differently.
- EPDM is synthetic rubber, usually black. It cannot be heat-welded, so seams are taped. It handles cold well and has a long track record.
- PVC is welded like TPO and resists grease and chemicals better, which is why it is common on restaurants.
- TPO sits between them: welded seams like PVC, generally lower cost, and white as standard.
Why white matters
A white membrane reflects much of the sun’s energy instead of soaking it up. The Department of Energy’s guide to cool roofs explains that this lowers roof surface temperatures and cooling loads, with the biggest benefit on air-conditioned buildings in hot, sunny climates. ENERGY STAR lists roof products that meet its reflectance criteria.
Common TPO problems
- Seams that were never welded properly and open after a few years.
- Punctures from foot traffic, dropped screws and hail.
- Flashings that pull away at curbs and walls.
- Surface cracking on older or thinner sheets.
All are repairable with a welded TPO patch over a cleaned area. See TPO roof repair for what that involves.
Is it safe to check a TPO roof yourself?
Wet TPO is slippery, and flat roofs have unprotected edges and skylights. OSHA’s fall protection rule applies to construction work near those edges, and it is good sense for anyone else too. Look for leaks from inside and leave the roof walk to a crew with fall protection.
If your TPO roof is leaking or due a check, tell us where the building is and we will look for a commercial roof repair specialist who covers it.