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What is TPO roofing?

The white roof on the new warehouse, the school and the strip mall: a thermoplastic sheet whose seams are welded with hot air into one continuous membrane.

Updated September 12, 2026 · Every figure links to its source · Sources

DefinitionSystemAlso called: thermoplastic polyolefin, thermoplastic single-ply, white roof

TPO roofing — a single-ply roof membrane of thermoplastic polyolefin, a reinforced plastic sheet, usually white, whose seams are fused with hot air into a single continuous membrane, installed mechanically fastened, fully adhered or ballasted on low-slope roofs; the Single Ply Roofing Industry represents its manufacturers, and the 2021 IRC, Section R905.13 regulates it as thermoplastic single-ply roofing.

What it is

A thermoplastic softens when heated and hardens again when cooled, and that is the whole trick of TPO: a hot-air welder run along the lap of two sheets melts them into one, with no adhesive, tape or flame. The membrane is a polyolefin blend over a polyester scrim, supplied in wide rolls, usually white for reflectance and also in grey and tan. On the roof it is either fastened through the laps with plates and screws (the commonest, and quickest), glued down over the whole surface, or laid loose under ballast; the details at walls, curbs, drains and pipes are welded from the same material.

The IRC, Section R905.13 sets the rules for houses — a design slope of at least one-quarter unit in twelve, the ASTM standard for the sheet (D6878 for TPO), and installation per the manufacturer — and the IBC, Section 1507.13 does the same for other buildings. The SPRI standards the codes reference cover wind design and edge securement.

Why it matters

TPO took the low-slope market for three reasons: welded seams, which are as strong as the sheet; a white surface, which the EPA notes reflects sunlight and lowers roof temperature and cooling load — the Cool Roof Rating Council rates products for that; and speed, since a mechanically fastened TPO roof goes down quickly. Its weaknesses are the ones of any single sheet: a puncture is a leak, the membrane's formulation has changed over the decades and older sheets have aged unevenly, and welding is a skill — a weld that looks fine and is not is the failure mode.

The choice most owners face is TPO against EPDM, and increasingly TPO against PVC, its more expensive thermoplastic cousin with better chemical resistance. The directory's comparison of TPO and EPDM sets out the trade-offs.

What it costs and who does it

Priced by the square, with the membrane thickness, the attachment method, the insulation and cover board beneath, the number of penetrations and the edge and wall flashing as variables; tear-off of an old roof and wet insulation adds to it, and on many buildings a TPO roof is installed over the old one where the code allows. Commercial roofing contractors do most TPO, and manufacturers certify the installers whose welds they will warrant. The directory's flat-roof replacement cost guide explains how those estimates are built.

Frequently asked questions

Short answers; the sections above carry the detail and the sources.

How long does a TPO roof last?
Manufacturers warrant TPO systems for terms that depend on the membrane thickness and the attachment; the field record is shorter than EPDM’s because the product is younger and early formulations varied. Thicker sheets, a certified installer and sound drainage are what lengthen it.
Is TPO better than EPDM?
It is different: TPO is white, reflective and heat-welded; EPDM is black rubber with taped seams and the longer track record. In a hot climate on an air-conditioned building TPO’s reflectance is an advantage; in a cold one EPDM’s flexibility is. The contractor’s experience with each matters as much as the material.
Can TPO be installed on a house?
Yes, on a low-slope section — a porch, an addition, a modern flat-roofed house — under the IRC’s Section R905.13, on a slope of at least a quarter inch per foot. Residential roofers with single-ply certification do such work.

See also

Next step

Find a roofer who does this

A welded seam is only as good as the hand on the welder; ask whether the crew is certified by the membrane's manufacturer. The directory lists roofing contractors by state and city.

Find a TPO roofing contractor

Sources

  1. Single Ply Roofing Industry — SPRI
  2. 2021 International Residential Code, Chapter 9: Roof Assemblies — International Code Council (ICC)
  3. 2021 International Building Code, Chapter 15: Roof Assemblies and Rooftop Structures — International Code Council (ICC)
  4. Using cool roofs to reduce heat islands — U.S. Environmental Protection Agency
  5. Cool Roof Rating Council — Cool Roof Rating Council (CRRC)