At a glance
- Small flat roof (average)
- About $7,400
- 2,000 sq ft flat roof
- $13,000 – $25,000
- Cost per sq ft, installed
- $4 – $13
- Typical lifespan
- 15 – 20 years
TPO and EPDM are the most common membranes. PVC and spray foam last longest; rolled roofing is cheapest but shortest-lived.
How much does it cost to replace a flat roof?
Smaller residential flat roofs, such as garages, porches and additions, often cost about $3,300 to $11,600 to replace, with an average near $7,400. A full 2,000 sq ft flat roof typically runs about $13,000 to $25,000, depending on the membrane.
Most materials cost $4 to $13 per square foot installed. The final price depends on the membrane you choose, how much old roofing has to come off, whether you add insulation, and the condition of the deck underneath.
Flat roof cost by material
| Material | Installed per sq ft | 1,000 sq ft roof | Typical lifespan |
|---|---|---|---|
| TPO single-ply | $6.00 – $12.00 | $6,000 – $12,000 | 15–30 yrs |
| EPDM rubber | $5.50 – $12.00 | $5,500 – $12,000 | 10–15 yrs |
| PVC single-ply | $6.50 – $13.00 | $6,500 – $13,000 | 20–40 yrs |
| Modified bitumen | $5.00 – $10.00 | $5,000 – $10,000 | 10–20 yrs |
| Built-up (tar & gravel) | $5.50 – $11.00 | $5,500 – $11,000 | 15–25 yrs |
| Rolled asphalt | $4.00 – $6.50 | $4,000 – $6,500 | 8–12 yrs |
| Spray polyurethane foam | $4.50 – $7.00 | $4,500 – $7,000 | 20–40 yrs |
Installed prices include materials and labor but not tear-off, insulation, decking repairs or permits.
Flat roof replacement cost by size
For a TPO roof with one membrane layer torn off and a permit, at average prices:
| Roof area | Low | Typical | High |
|---|---|---|---|
| 500 sq ft | $3,500 | $5,450 | $7,350 |
| 1,000 sq ft | $6,750 | $10,450 | $14,100 |
| 1,500 sq ft | $10,000 | $15,450 | $20,850 |
| 2,000 sq ft | $13,250 | $20,450 | $27,600 |
| 3,000 sq ft | $19,750 | $30,450 | $41,100 |
Flat roof materials compared
- TPO is a heat-welded single-ply membrane, usually white, that reflects sunlight and helps keep the building cooler. It's one of the most common choices for new flat roofs.
- EPDM is a black synthetic rubber sheet that's easy to install and repair. It absorbs heat, which can help in cold climates.
- PVC is a welded single-ply membrane that resists chemicals, grease and standing water well. It usually costs a little more than TPO.
- Modified bitumen is asphalt reinforced with polymers, applied in rolls with heat or adhesive. It handles foot traffic well.
- Built-up roofing (BUR) layers asphalt and reinforcing felt, often topped with gravel. It's heavy and durable but slow and messy to install and remove.
- Rolled asphalt is the budget option for sheds, porches and small garages, with the shortest lifespan.
- Spray foam (SPF) is sprayed on as a seamless, insulating layer and needs a protective coating that's renewed every few years.
What affects the cost
- Tear-off. Removing one membrane layer costs about $0.50 to $1.50 per sq ft. Tar and gravel or multiple layers can run $1.50 to $5.
- Insulation. Adding about 2 to 3 inches of polyiso board costs roughly $0.90 to $1.50 per sq ft, and many codes require insulation on a full replacement.
- Deck condition. Water often rots the wood under a leaking flat roof. Replacing damaged decking costs about $2 to $8 per sq ft.
- Drainage. Fixing ponding water may require tapered insulation, new drains or scuppers.
- Penetrations and edges. HVAC units, skylights, vents and parapet walls all need extra flashing and labor.
- Access and location. Hard-to-reach roofs and higher cost-of-living areas cost more. Permits typically run $250 to $600.
Worked example
A 30 ft × 40 ft flat roof with an old tar and gravel roof, replaced with EPDM and new insulation at average prices:
- Roof area: 30 × 40 = 1,200 sq ft.
- EPDM installed: 1,200 × $5.50 to $12.00 = $6,600 to $14,400.
- Tar and gravel tear-off: 1,200 × $1.50 to $5.00 = $1,800 to $6,000.
- Polyiso insulation: 1,200 × $0.90 to $1.50 = $1,080 to $1,800.
- Permit: $250 to $600.
- Total: about $9,750 to $22,800, with a typical price near $16,250.
Recover or full replacement?
A recover installs a new membrane over the existing roof and skips tear-off costs. It can work when the old roof is dry, firmly attached and only one layer thick. If the insulation is wet, the deck is soft, or codes don't allow another layer, a full tear-off is the safer choice. Ask your roofer for a moisture survey before deciding.
How to save on a flat roof replacement
- Get at least three written quotes that list the membrane brand and thickness, insulation, tear-off and decking allowance.
- Compare cost per year. A longer-lasting membrane can be cheaper over time, as the comparison table above shows.
- Fix drainage now. Paying for tapered insulation or better drains costs less than replacing a roof early because of ponding water.
- Check your insurance if the roof was damaged by a storm, and file before work starts.
Frequently asked questions
How much does it cost to replace a flat roof?
Smaller residential flat roofs, such as garages and additions, often cost about $3,300 to $11,600, with an average near $7,400. A full 2,000 sq ft flat roof typically runs about $13,000 to $25,000 depending on the material.
How much does a flat roof cost per square foot?
Most flat roof materials cost about $4 to $13 per square foot installed. Tear-off, insulation, decking repairs and permits add to that.
What is the cheapest flat roof material?
Rolled asphalt roofing and spray foam usually have the lowest upfront cost, but rolled roofing has the shortest lifespan, so it can cost more per year of service.
Can you put a new flat roof over the old one?
Sometimes. A recover can skip tear-off costs when the existing roof is dry and sound, but local codes limit how many layers are allowed and wet insulation must be removed. A roofer should inspect and test the roof first.
How long does a flat roof last?
Lifespans range from about 8 to 12 years for rolled roofing to 20 to 40 years for PVC and spray foam. Most flat roofs last 15 to 20 years with regular maintenance.
TPO or EPDM: which costs less?
Their installed price ranges overlap: EPDM runs about $5.50 to $12 per square foot and TPO about $6 to $12. EPDM is often slightly cheaper to install, while TPO's white surface reflects more heat.
How we calculate
Installed prices per square foot blend published cost data from the sources below, from 2023 through 2026. Where sources disagree, we use a range that covers the bulk of their figures. Tear-off rates come from RoofCalc and HomeAdvisor, insulation from RoofCalc's polyiso pricing, and permits from HomeAdvisor. Decking repairs use $2 to $8 per sq ft, the same rate as our roof replacement cost calculator.
Some inputs are our own planning assumptions, stated so you can judge them: the cost-of-living setting moves labor and material costs by −10% or +15%, the insulation line assumes about 2 to 3 inches of polyiso, and lifespans blend the ranges published by the sources below. The "typical" price is the midpoint of the range.
This is an estimate, not a quote. Real prices depend on your roof's condition, drainage, access and local labor rates. Always get written quotes from licensed roofers before you hire.
Sources
- HomeAdvisor: Flat roof replacement cost (updated June 2026)
- This Old House: Flat roof replacement cost (updated March 2026)
- RoofCalc: Flat roof replacement cost estimator and flat roof insulation cost
- RoofingCalc: Best flat roof materials (2024)