A flat or low-slope roof is priced differently from a shingled one, and the material you choose drives most of the cost. Replacing one typically runs somewhere around 5 to 10 dollars per square foot installed, though the range is wider at the extremes. Here is what a flat roof costs by material, how long each system lasts, and what pushes the price up.
The math is simpler on a flat roof
One nice thing about a flat roof is that the measurement is straightforward. A steep shingled roof has more surface than the ground it covers, so roofers multiply the footprint by a pitch factor. A flat roof does not, so its square footage maps directly to the footprint, and a roofing square of 100 square feet is just that.
What it costs by material
Flat roofs use membrane and asphalt-based systems rather than shingles. Here are typical installed ranges in 2026:
- EPDM (black rubber membrane): about 3.50 to 8 dollars per square foot, the cheapest option.
- TPO (white single-ply): about 4 to 7 dollars, and a strong pick for hot climates because the white surface reflects heat.
- PVC (white single-ply): about 5 to 8 dollars, the most durable single-ply.
- Modified bitumen (rolled asphalt): about 4 to 7 dollars.
- Built-up roof, or tar and gravel: about 4 to 10 dollars.
- Spray foam: about 3.50 to 10 dollars, seamless and recoatable.
On a typical 1,600 square foot flat roof, that works out to roughly 8,000 to 16,000 dollars. A small, simple roof can be less, and a large PVC or foam roof more.
For how these systems actually differ beyond price, see our flat roof materials compared.
How long each lasts
Cost only makes sense next to lifespan, and here the systems vary. As rough ranges, EPDM and TPO last around 15 to 25 years, PVC 15 to 30 or more, modified bitumen 10 to 20, and built-up 20 to 30. Spray foam is recoatable, so with maintenance it can last a very long time. Lifespans move a lot with quality and upkeep, so treat these as ballparks.
What drives the price
- The membrane you choose, which is the biggest lever.
- The roof size and how many penetrations it has, like vents and HVAC curbs.
- Tearing off the old roof, which adds about 1 to 3 dollars per square foot.
- The condition of the decking and insulation underneath.
- Drainage, since a flat roof needs a way to shed water and avoid ponding.
These mirror the drivers on any roof, which we cover in what affects roof replacement cost.
In the heat, go white
On a hot-climate flat roof, a reflective white membrane like TPO or PVC keeps the roof and the rooms below far cooler than black EPDM, which soaks up the sun. The energy savings can offset the slightly higher price over time.
Do you even have a flat roof?
Flat roofs are most common on commercial buildings, but plenty of homes have them, on modern designs, room additions, porches, carports, and garages. Even a mostly-shingled house can have a low-slope section that needs a membrane rather than shingles, so it is worth knowing the cost.
“On a flat roof, the membrane is the price. Pick the system for your climate and how long you plan to stay, then weigh it against the lifespan.”
Get a real number
Because so much depends on the membrane and the decking underneath, an in-person quote is the only way to a real figure. See how roofers price per square and how much a new roof costs overall.
With Hommy you can post your job once and get quotes from vetted local roofers who install flat roofs, each with real ratings from other homeowners, so you can compare systems and prices.
