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Flat Roof Replacement Cost Calculator

A flat roof replacement averages $7,430, ranging from about $1,200 to $24,000 depending on membrane type and size, per Angi. For a typical 1,500 sq ft flat roof, EPDM rubber runs roughly $6,200–$16,000 installed — usually the cheapest membrane, with PVC the most expensive. Pick your membrane, surface and insulation needs below for a tighter range.

Select your membrane type, roof surface and whether you need an insulation/code-compliance upgrade on top of the standard permit. The range updates using published per-square-foot cost data for low-slope and flat roofs — it is not a quote.

$3,250 – $8,500

Estimated installed cost for your selections, before local quotes.

Assumes a residential low-slope or flat roof with standard access, not a large commercial deck. Excludes major structural repairs and drainage rework beyond a standard tear-off. Confirm insulation R-value requirements with your local building code before budgeting a specific number.

Ranges compiled from the published sources listed at the bottom of this page (accessed July 2026). How we build and check our tools →

EPDM vs. TPO vs. PVC vs. modified bitumen: cost by membrane

For a typical 1,500 sq ft flat roof, HomeGuide prices EPDM rubber (the most common flat-roof membrane) at $3.50–$10.00 per square foot, or $6,200–$16,000 installed — usually the cheapest of the four, and it lasts 15–20 years. TPO runs a similar $4–$10/sq ft ($7,700–$14,000 total) and lasts longer, 10–25 years. PVC is the priciest membrane at $5–$12/sq ft (about $7,500–$18,000 for the same size), reflecting better chemical and puncture resistance. Modified bitumen is the cheapest overall at $4.00–$7.50/sq ft ($4,900–$14,600 total). Angi's independent figures corroborate the ranking: modified bitumen $4–$8/sq ft, TPO $4–$14/sq ft, EPDM $5–$13/sq ft.

Why flat roofs cost more per square foot than shingled roofs

This Old House's material table (sourced from Homewyse) prices flat-roof membranes at $7–$21 per square foot installed — several times the $3.40–$5.95/sq ft that RoofingCalculator.com cites for asphalt shingles on a pitched roof. The gap isn't the membrane material itself; it's labor and detailing. A flat roof has to be fully waterproofed rather than shedding water by gravity and overlap, so seams, drains, flashing and edge details all need to be sealed by hand — work a shingle roof simply doesn't require.

Cost by roof surface

Because flat roofs are priced almost linearly by square foot (no pitch multiplier to account for), a small 700 sq ft roof costs roughly half of the 1,500 sq ft reference size used above, and a 2,500 sq ft roof costs about 1.7× as much. If your flat roof also covers an attached garage, porch or addition, measure the combined surface — contractors price the whole deck as one job.

Insulation and code compliance costs

A standard roofing permit costs $150 to $500 and is often folded into the contractor's estimate, per HomeGuide. If your roof deck needs an insulation upgrade to meet current energy code — common on older flat roofs — spray foam insulation runs an additional $1.50 to $5.00 per square foot (rubber/membrane roofs typically use rigid polyiso boards instead of spray foam, priced in the same range). On a 1,500 sq ft roof that's roughly $2,250–$7,500 on top of the membrane and permit cost — the biggest single add-on in this estimator.

Tear-off costs for an old flat roof

Removing and disposing of the existing flat roofing costs $1 to $2 per square foot including disposal fees, per HomeGuide — about $1,500–$3,000 on a 1,500 sq ft roof. Because flat roofs are more likely to trap moisture under multiple old layers than pitched shingle roofs, tear-off (rather than overlay) is the more common recommendation from roofers even when code would technically allow layering.

Is this a job for a specialized flat-roof contractor?

Membrane roofing (EPDM/TPO/PVC seaming, hot-air welding, torch-applied modified bitumen) is a different trade skill set from asphalt shingle installation, so ask any quote specifically about flat-roof or low-slope experience, not just "roofing" in general. Compare this page with the standard roof replacement cost calculator if part of your property has a pitched section, the water heater replacement cost estimator for other home-system budgeting, and the square footage calculator to measure your roof surface before requesting quotes.

Frequently asked questions

How much does a flat roof replacement cost on average?

Angi puts the average at $7,430, with a typical range of $1,200 to $24,000 depending mostly on roof size and membrane type. For a common 1,500 sq ft roof, EPDM or modified bitumen usually land in the $4,900–$16,000 range installed.

What is the cheapest flat roof material?

Modified bitumen is typically the cheapest, at $4.00–$7.50 per square foot ($4,900–$14,600 installed on a 1,500 sq ft roof), per HomeGuide. Angi's independent figures ($4–$8/sq ft) confirm it as the low end.

Is EPDM cheaper than TPO?

They overlap, but EPDM is usually slightly cheaper: $3.50–$10.00/sq ft ($6,200–$16,000 installed on 1,500 sq ft) versus TPO's $4–$10/sq ft ($7,700–$14,000), per HomeGuide. TPO tends to last longer (10–25 years vs. EPDM's 15–20).

Is PVC roofing more expensive than EPDM?

Yes. PVC membrane runs $5 to $12 per square foot installed versus EPDM's $3.50 to $10.00, per HomeGuide — PVC is the priciest of the four common flat-roof membranes, reflecting better chemical and puncture resistance.

How much does it cost to remove an old flat roof?

Tear-off and disposal costs $1 to $2 per square foot including disposal fees, per HomeGuide — about $1,500 to $3,000 on a typical 1,500 sq ft flat roof.

Do I need a permit to replace a flat roof?

In most jurisdictions, yes — a roofing permit typically costs $150 to $500, per HomeGuide, and contractors often fold this into their quoted price rather than billing it separately.

Does a flat roof need extra insulation?

Often, especially on older roofs being brought up to current energy code. Spray foam insulation (or rigid polyiso boards for membrane roofs) costs an additional $1.50 to $5.00 per square foot, per HomeGuide — roughly $2,250 to $7,500 on a 1,500 sq ft roof.

Why do flat roofs cost more per square foot than shingle roofs?

This Old House's data shows flat-roof membranes at $7–$21/sq ft versus $3.40–$5.95/sq ft for pitched asphalt shingles, mainly because a flat roof must be fully waterproofed by hand (seams, drains, flashing) rather than shedding water by pitch and overlap.

How long does a flat roof last?

It depends on the membrane: EPDM rubber lasts about 15–20 years and TPO 10–25 years, per HomeGuide. Modified bitumen and PVC roofs, properly maintained, typically fall in a similar range.

Sources

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Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →