2026 flat roofing costs
Flat Roof Cost
A TPO flat roof costs about $4.57 to $8.12 per square foot installed in 2026, so a 1,500 sq ft roof runs $6,856 to $12,185 including insulation board and a permit. The membrane itself is only $1.00 to $2.50 a square foot; insulation and labor make up most of the bill. The calculator prices TPO.
Enter your roof area for a 2026 membrane roofing estimate covering material, labor and permit.
Estimate a flat roof
Low-slope roofs are measured directly, so there is no pitch multiplier to apply.
Estimated total
materials + labor + permit
- Roofing squares
- 15.0
- Materials
- $4,125 – $8,193
- Labor
- $2,581 – $3,491
- Per sq ft
- $4.57 – $8.12
- Materials 67% · $8,193
- Labor 29% · $3,491
- Permit 4% · $500
Material breakdown
Quantities are what gets ordered for the job in the calculator above: whole bundles, sticks and rolls, with the waste allowance on cut materials.
| Material | Qty | Cost |
|---|---|---|
| TPO Membrane (60 mil) | 1,620 SF | $1,620 – $4,050 |
| Polyiso Insulation Board | 1,620 SF | $1,782 – $2,916 |
| TPO Flashing & Accessories | 195 LF | $390 – $683 |
| Termination Bar & Plates | 195 LF | $293 – $488 |
| 1-in Smooth Shank Electro-galvanized Roofing Nails 244 -Per Box | 8 BOX | $41 – $57 |
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TPO, EPDM and modified bitumen
TPO is a white thermoplastic sheet, heat-welded at the seams. It reflects solar gain, which cuts cooling load, and welded seams are the strongest joint of the three. EPDM is black synthetic rubber, seamed with tape or adhesive; it is the most forgiving to install and repair but absorbs heat. Modified bitumen is asphalt-based roll roofing, torch- or cold-applied in two or three plies, and is the most puncture-resistant of the three.
For a house with a flat section, EPDM is usually the pragmatic choice, because repairs are simple and a competent roofer can patch it in one visit. For a large commercial deck in a hot climate, TPO usually wins on energy.
Drainage is the whole game
Flat roofs are never truly flat. Code requires at least 1/4 inch per foot of fall toward drains, and where that slope is missing you get ponding. Standing water is what kills membrane roofs. It works seams, accelerates UV breakdown and multiplies any small puncture into a leak.
If your flat roof ponds after rain, fixing the slope with tapered insulation costs more than a straight membrane swap but is the only durable answer. Re-covering over a ponding deck just buys a few years.