TPO roofing: what it is, how it's installed, and what it costs
TPO (thermoplastic polyolefin) is a single-ply membrane for flat and low-slope roofs, made to ASTM D6878. It's fully adhered or mechanically attached to the deck or insulation, with the seams welded. The code calls for at least a 1/4:12 slope. A 600 sq ft garage roof in 60 mil, fully adhered, typically comes to $5,000.
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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What it is
TPO (thermoplastic polyolefin) is a single-ply roof membrane: one sheet, laid over the deck or insulation board on flat and low-slope roofs. It’s a thermoplastic, so heat softens it, which is how the seams are joined: the overlapping edges are welded with hot air into one sheet.
In the code, TPO is a thermoplastic single-ply roof covering, with PVC and KEE in the same group, made to ASTM D6878 (PVC is ASTM D4434 and KEE ASTM D6754) (IRC R905.13.2). EPDM rubber is the other kind of single-ply, a thermoset (R905.12).
How it’s installed
- Tear off the old roof and repair the deck.
- Lay insulation board where the roof needs it, fastened or adhered.
- Lay the membrane: fully adhered with bonding adhesive, or mechanically attached with fasteners and plates at the seams.
- Weld the seams with hot air, then probe them for gaps.
- Flash the edges, curbs and pipes with membrane and metal edge made for TPO.
The roof goes on by the code and the maker’s instructions (IRC R905.13.3).
What the code says
- Slope: a design slope of at least 1/4 inch per foot (2%) (IRC R905.13.1).
- Material: TPO to ASTM D6878 (R905.13.2).
What a TPO roof costs
Priced the way a contractor’s estimate is priced: a 60 mil single-ply membrane, fully adhered, with the old roof torn off, 10% over the roof for laps and turn-ups at the edges.
| Roof | Range | Typical |
|---|---|---|
| A porch or small addition, 300 sq ft | $2,200 to $2,950 | $2,500 |
| A two-car garage, 600 sq ft | $4,450 to $5,900 | $5,000 |
| A flat-roofed house, 1,500 sq ft | $11,100 to $14,800 | $12,500 |
Totals include the contractor’s overhead and profit (20%) and the state’s average sales tax. Each range runs from the lower-priced parts of the country to the higher-priced ones. Edge metal, insulation, new decking and drains are extra.
TPO or EPDM
| TPO | EPDM | |
|---|---|---|
| Kind | Thermoplastic | Thermoset rubber |
| Seams | Welded with hot air | Adhesive or seam tape |
| Standard | ASTM D6878 | ASTM D4637 or D5019 |
| Lowest slope | 1/4:12 | 1/4:12 |
| A 600 sq ft garage roof | $4,450 to $5,900 | $5,500 to $7,600 |
The EPDM guide covers the rubber roof, and the modified bitumen guide the asphalt one.
Common questions
How much does a TPO roof cost per square foot?
About $7.25 to $10.00 a sq ft of roof for 60 mil, fully adhered, with the old roof torn off, overhead, profit and sales tax.
Is TPO better than EPDM?
They’re both single-ply membranes with the same minimum slope. TPO’s seams are welded; EPDM’s are glued or taped. The table above prices both on the same roof, the same way.
Can TPO go on a house?
Yes, on the flat and low-slope parts: porches, additions, dormers and flat-roofed houses, at a slope of at least 1/4:12.