Replacing a flat roof typically costs about $7 to $13 per square foot for most materials, which puts a 2,000 square foot roof somewhere between $13,000 and $25,000. Metal costs more. The material, the size and what the crew finds under the old roof decide where you land.
The short version
- Most flat roofing materials run about $7 to $13 per square foot, and metal runs higher.
- Tear-off, rotted decking, drains and edge metal are the extras that move the total.
- A small low section on a house often has a minimum price, whatever its size.
- Repair makes sense until the leaks keep coming back.
- A free roof inspection tells you which side of that line you are on.
What does a flat roof cost per square foot?
Most flat roofing materials cost between $7 and $13 per square foot (opens in a new tab), according to This Old House, which builds those numbers from Homewyse estimates. The same publisher’s replacement guide breaks it out by material, and we have added what each one comes to on a 2,000 square foot roof.
| Material | Per square foot | On a 2,000 sq ft roof |
|---|---|---|
| Modified bitumen | $7 to $9 | $13,357 to $18,018 |
| Built-up roof | $7 to $9 | $14,158 to $18,911 |
| TPO | $8 to $11 | $16,266 to $21,405 |
| Rubber (EPDM) | $9 to $13 | $18,862 to $25,108 |
| Metal | $15 to $21 | $29,989 to $42,166 |
Those are builder-grade materials at medium labor cost (opens in a new tab), not a quote for your house. Treat the table as a way to see how the materials compare with each other. Our article on the best material for a flat roof covers what you get for the difference.
What is the average price of a new flat roof?
The same guide puts the average at around $24,510 (opens in a new tab), with a full spread of $11,311 to $37,709 or more. That is a wide spread, and it should be. A flat roof over a garage and a flat roof over a whole row house are different jobs.
Size is the biggest lever. Roofers price in squares, and one square is 100 square feet. Ask any roofer to give you the measured square count, so you can compare bids on the same size.
Why does a small flat roof still cost a lot?
Small jobs carry a minimum, because getting a crew, a dumpster and materials to the house costs the same for a small roof as a big one. On our side, a section too flat for shingles (under a 2/12 pitch) needs modified bitumen, TPO or standing seam metal, and that work typically runs a minimum of $2,500 to $5,000 in this area.
That is a typical range for the work around Ellicott City, not a quote. We see this most on porch roofs, bump-outs and additions tied into a pitched roof.
What adds to the price of a flat roof?
The extras are where a quote and a final bill drift apart. These are the usual ones:
- Tear-off. This Old House says contractors add removing old roofing (opens in a new tab) to the project total, and that an overlay, new material laid over the old, will likely cost less up front.
- Rotted decking. Decking is the wood under the roof. Where it is soft or wet, it gets replaced, and we price that by the sheet at typically $70 to $150 installed.
- Drains, edges and flashing. The guide lists drainage, sealant and permits (opens in a new tab) as additional costs.
- Things on the roof. Skylights typically run $800 to $2,000 or more each, and replacing one during the reroof is the cheapest time to do it.
- Old roofing with asbestos. Roofs from before 1980 can contain it, and removal typically runs $3 to $8 per square foot on top of the roof itself.
For the unknowns, the guide suggests budgeting another $1,200 to $1,800 (opens in a new tab) for deck repairs or flashing work. We would add that a wet, soft roof can run past that.
Is it cheaper to put a new flat roof over the old one?
Sometimes, but the savings come with strings. This Old House warns that an overlay can void warranties and mask underlying damage (opens in a new tab). The guide also notes that most building codes limit a roof to two layers, so a second overlay is not an option later.
There is a quieter problem. If the old membrane is holding water underneath, covering it traps that water. We would rather open it up, see what is there and price the real job. A hidden layer of old flat roof under shingles is the same story: it is a surprise that shows up at tear-off.
When should you replace instead of repair?
Replace when repairs get too expensive or the leaks keep returning. That is how This Old House puts it: replacement makes sense when repairs become too expensive (opens in a new tab) or leaks keep coming back.
A repair to a low-slope membrane typically runs $2,500 to $6,000 in our area, and that is a range, not a quote. Past a couple of those, the math shifts. The Department of Energy puts the line the same way: if a roof is in poor condition or near the end of its life, it is usually best to re-cover, replace or retrofit (opens in a new tab) it. A coating can buy time on a sound roof, and our article on whether a flat roof coating is worth it covers where it does and does not.
Our view is repair first whenever the roof allows. If a full replacement is not needed, we would rather fix the spot and save you the money.
Common questions
How long does a flat roof last?
It depends on the material, and the published numbers do not agree. This Old House says flat roofs generally last 15 to 20 years (opens in a new tab), while its guide to flat roof types says EPDM can reach up to 50 years. Treat the high numbers as the best case, with seams and drains kept up.
Does the price include permits and gutters?
Permits and the final inspection are passed through at cost on the jobs we do. Gutters and gutter guards are separate, and so is any rotted fascia or trim carpentry. Ask any roofer you talk to for a line-by-line list so you can compare like with like.
Can I pay for a new flat roof over time?
You can check payment options through our financing partner. Our financing page explains how that works, and we do not quote rates or payments in an article.
What to do next
Before you price anything, find out what you have. Our free roof inspection includes a boots-on-the-roof walk and a written report with photos, and it does not obligate you to book work. If the roof is past repair, our flat roof installation page explains what we put on and where.
