How much does a flat roof replacement cost?
Ashburn, VA

How much does a flat roof replacement cost?

Ashburn, VA

How much does a flat roof replacement cost?

$3 – $11cost per square foot installed
$4,000 – $16,800average total cost to replace

Get free estimates for your project or view our cost guide below:

$3 – $11 cost per square foot installed

$4,000 – $16,800 average total cost to replace


Get free estimates for your project or view our cost guide below:
Jennifer Carlson
Written by
Jennifer Carlson
Edited by
Kristen Cramer
Fact-checked by
Tom Grupa

Flat roof replacement cost

Flat roof replacement costs $3 to $11 per square foot or $4,000 to $16,800 on average, depending on the size and material. Flat roof material prices are $0.15 to $8.00 per square foot. New flat roof installation is most common on commercial buildings and garages.

Flat roof replacement cost
Roof size (square feet) Average cost to replace
800 $2,400 – $8,800
1,000 $3,000 – $11,000
1,500 $4,500 – $16,500
2,000 $6,000 – $22,000
2,500 $7,500 – $27,500
3,000 $9,000 – $33,000
3,500 $10,500 – $38,500

Flat roof replacement cost calculator

The following table shows the average cost to install or replace a flat roof.

Flat roof replacement cost - chart
Flat roof replacement cost - chart
Flat roof replacement cost
National average cost $10,800
Minimum cost $1,000
Maximum cost $30,000
Average range $4,000 to $16,800

Average flat roof cost per square foot

Residential flat roof replacement costs $3 to $11 per square foot, while commercial flat roof construction costs $4 to $11 per square foot on average, including labor and materials.

Flat roof cost per square foot
Type Cost per square foot installed
Residential $3 – $11
Commercial $4 – $11

Roofers typically estimate the cost by the square. One square covers 100 square feet.

Commercial flat roof cost per square foot

A commercial flat roof costs $4 to $11 per square foot, depending on the material and accessibility. Large commercial roofs may qualify for bulk discounts on materials. However, consider the cost of cranes, storage, and any special permits when calculating prices.

New flat roof cost by type

A new flat roof costs $3 to $11 per square foot, depending on the material. Rolled asphalt is the most affordable option but has the shortest lifespan. Membrane roofing is popular, strong, and easy to install. PVC, metal, and concrete roofing are the most durable but expensive options.

New flat roof cost by type
Material Cost per square foot installed
Tar & gravel / built-up roof cost $3.50 – $7.50
EPDM rubber membrane roof cost $3.50 – $10.00
TPO membrane roof cost $4.00 – $10.00
PVC membrane roof cost $5.00 – $12.00
Fiberglass / GRP roof cost $3.50 – $7.50
Modified bitumen roof cost $4.00 – $7.50
Rolled asphalt roof cost $2.00 – $5.00
Spray foam roof cost $3.50 – $7.00
Metal roof cost $5.00 – $16.00
Concrete roof cost $4.00 – $15.00

Flat rubber / EPDM roof replacement cost

The most common flat rubber roof types are EPDM, TPO, and PVC:

  • EPDM roofing costs $4 to $10 per square foot or $6,200 to $16,000 with installation. Ethylene propylene diene monomer (EPDM), a recyclable rubber, is the cheapest membrane roof option and lasts 15 to 20 years on average.

  • TPO roofing costs $4 to $10 per square foot or $7,700 to $14,000 total installed. Thermoplastic polyolefin (TPO) is a blend of plastic and rubber and lasts 10 to 25 years.

  • Polyvinyl chloride (PVC) roofing costs $5 to $12 per square foot with installation. PVC is the most expensive rubber roof type but is also the most durable, lasting 20 to 30 years on average.

EPDM rubber roofing membrane installed on residential house
EPDM rubber roofing membrane installed on residential house

Modified bitumen flat roof cost

Modified bitumen roofing costs $4.00 to $7.50 per square foot or $4,900 to $14,600 installed. This roof type is flexible, UV-resistant, and lasts 10 to 20 years. While heat welding is often used to apply modified bitumen and can be dangerous, many brands make self-adhesive rolls.

Torch-down modified bitumen roofing installation
Torch-down modified bitumen roofing installation

Fiberglass / GRP flat roof cost

A fiberglass flat roof costs $3.50 to $7.50 per square foot installed. Fiberglass roofing, also called glass-reinforced plastic (GRP), is durable, lightweight, and waterproof but is unsuitable for large roofs. GRP roofs last 25 to 50 years.

Built-up felt roofing cost

Built-up roofing (BUR) costs $3.50 to $7.50 per square foot or $4,500 to $12,600 total with installation. Built-up roofs, also called tar and gravel roofs, are made with layers of asphalt sheets, tar, and felt topped with rocks or gravel. Built-up roofing lasts 20 to 30 years.

Tar and gravel roof replacement
Tar and gravel roof replacement

Flat metal roofing cost

Flat metal roofing costs $5 to $16 per square foot or $7,500 and $40,000 total. Metal roofs are costly but more durable than other materials, lasting 30 to 80+ years. Metal roofs often reduce home insurance premiums.

Flat roof installation cost factors

The following factors affect the cost to install a flat roof:

  • Roof complexity – Complex roof shapes, multiple penetrations, and hard-to-access roofs increase labor costs.

  • Stories – Multiple stories, especially in commercial buildings, increase labor costs.

  • Application method – Ballasted roofs use rocks or gravel to secure the roofing material, while mechanically fastened roofs use metal plates and screws. Adhered roofs use glue or self-adhesive and cost more than the other methods.

  • Ventilation – A roof vent costs $200 to $700 with installation.

  • Roof drains – A roof drain costs $70 to $340 and prevents pooling water.

  • Extra underlayment Roof underlayment costs $0.75 to $4.00 per square foot installed.

  • Flat roof insulation Spray foam insulation costs $1.00 to $4.50 per square foot and is ideal for most flat roofs. Rubber flat roofs use polyiso insulation boards instead, which cost $0.50 to $3.00 per square foot with installation.

  • Overhangs Repairing eaves costs $500 to $2,600 or $9 to $34 per linear foot. Eaves, or overhanging roof edges, protect the walls and foundation from water damage.

  • FlashingRoof flashing repair costs $200 to $500. Replacing and resealing all flashing costs $400 to $1,000. Flashing prevents leaks around fixtures.

  • Parapet walls – A parapet is a low protective wall that is often covered with a metal cap. Repairing or replacing a parapet, its cap, or the surrounding flashing raises costs.

  • Region / location – TPO, built-up roofs, and PVC are best for hot climates, while EPDM and modified bitumen do well in cold climates. Metal and concrete roofs perform well in both.

  • Dump fees – Removing old flat roofing costs $1 to $2 per square foot, including disposal fees.

  • Permits and inspections – A roofing permit costs $150 to $500. Contractors often include the permit cost in the estimate.

New flat roof replacement on building
New flat roof replacement on building

Flat roof installation designs

  • Cold – A cold flat roof has insulation between the rafters. This design is cost-effective but not as effective as other insulation methods.

  • Warm – A warm flat roof has insulation on top of the decking instead of between the rafters. This design is energy-efficient, easy to install, and breathable but adds extra height to a roof.

  • Hybrid – A hybrid flat roof, or compact roof, combines warm and cold roofs. Most of the insulation in a hybrid roof is between the rafters, and some is on top of the decking. Hybrid roofs are highly efficient while minimizing the roof thickness.

  • Inverted – Inverted roofs have waterproofing beneath the insulation instead of above it to keep the roof warm during winter and cool in summer. Inverted roofs regulate temperatures well, but leaks are harder to locate and fix.

  • Tapered – A tapered roof system contains a slightly sloped insulation, allowing excess water to drain easily.

  • Curved – A curved flat roof has an arc shape, which sheds rain and snow easily. This roof type is new, eco-friendly, and requires less framework but is often more expensive than other designs.

  • Green – A green roof or eco-roof contains a layer of vegetation planted on top of the roofing material. This roof type is visually appealing and insulates well, but it can be expensive to install and maintain.

Garage flat roof replacement cost

Garage flat roof replacement costs $850 to $9,200, depending on the size and material.

  • A flat roof for a 1-car garage costs $850 to $3,100.

  • A flat roof for a 2-car garage costs $1,200 to $4,400.

  • A flat roof for a 3-car garage costs $2,500 to $9,200.

Flat roof tear-off cost

A flat roof tear-off costs $1 to $2 per square foot. Complete removal is necessary when the roof is 10 to 15 years old or needs extensive repairs.

Flat roof material prices

Flat roof material prices are $0.15 to $8.00 per square foot, depending on the type. Rolled asphalt is the cheapest, while metal and concrete roofing are the most expensive options.

Flat roof material prices
Type Material price per square foot*
Built-up / tar & gravel $1.50 – $2.70
EPDM membrane $0.50 – $2.50
TPO membrane $1.00 – $2.50
PVC membrane $1.50 – $3.00
Fiberglass / GRP $0.20 – $2.40
Modified bitumen $0.70 – $2.20
Rolled asphalt $0.15 – $0.50
Spray foam $1.50 – $3.00
Metal $3.00 – $8.00
Concrete $2.00 – $4.00

*Not including installation.

Flat roof labor construction and re-roofing cost

Labor for flat roof replacement costs $2.00 to $4.50 per square foot, depending on the material, location, and job complexity.

Frequently asked questions

What is a flat roof?

A flat roof is a roof with little to no slope or pitch. Flat roofs are used on commercial buildings and homes and are covered in a variety of materials designed to prevent water from pooling on the surface.

Flat roof pros and cons
Advantages Disadvantages
  • Affordable
  • Energy efficient
  • Potential garden or patio space
  • Modern appearance
  • Fast installation
  • Prone to pooling water
  • More maintenance than sloped roofs
  • Some types use hazardous torches or hot tar

How long does a flat roof last?

Flat roofs last 5 to 80 years, depending on the material.

Flat roof lifespan by material
Type Average lifespan (years)
Built-up 20 – 30
EPDM membrane 15 – 25
TPO membrane 10 – 25
PVC membrane 20 – 30
Fiberglass / GRP 25 – 50
Modified bitumen 10 – 20
Rolled asphalt 5 – 20
Spray foam 40 – 50
Metal 30 – 80
Concrete 50 – 60

How much does it cost to replace a flat roof with a pitched roof?

Replacing a flat roof with a pitched roof requires new trusses, roofing material, and siding. Framing a roof costs $9,000 to $37,500, depending on the size, material, and complexity. Chimneys, skylights, and HVAC pipes may also need to be extended or replaced.

How much do flat roof repairs and maintenance cost?

Flat roof repairs cost $2.50 to $10.00 per square foot or $300 to $1,100 on average, depending on the repair type and severity. Minor leak repair costs $150 to $500, while fixing extensive leaks and structural damage costs $1,200 to $3,000.

Flat roof maintenance costs depend on the material and weather. Coating a roof costs $1 to $4 per square foot or $500 to $2,000 total and increases its lifespan. Sweep flat roofs and clear gutters every six months or after storms.

Getting flat roof replacement estimates and quotes

Before hiring a roofing installer near you, be sure to:

  • Get three or more quotes to compare.

  • Read their reviews on HomeGuide and Google.

  • Look for companies with:

  • A state contractor license

  • National Roofing Contractors Association (NRCA) certification

  • Roof Coatings Manufacturers Association (RCMA) membership

  • International Association of Certified Home Inspectors (InterNACHI) certification

  • Select a licensed, insured, bonded company with 5+ years’ experience.

  • Be careful with extremely low or high price estimates.

  • Beware of companies who recommend a full roof replacement if only repairs are needed.

  • Verify the roofing contractor has experience with your roof type.

  • Ask for a clear written estimate and warranty before work begins.

  • Avoid large upfront payments. Instead, negotiate a payment schedule and save receipts.

Questions to ask

  • How long have you been repairing and building flat roofs?

  • Are you licensed, insured, and bonded?

  • Can you provide references for past work?

  • Are you a member of the NRCA? What certifications do you have?

  • Can you provide a detailed quote?

  • Does your quote include waste disposal or taxes?

  • Which material do you recommend for my roof, and why?

  • Which sealant or coating do you recommend for my roof, if any?

  • How long will the project take?

  • What will you do in the event of unexpected bad weather?

  • How will you access my roof? What safety precautions will you take?

  • Will you obtain any necessary permits?

  • What additional costs should I expect?

  • Do you offer financing?

  • What does your warranty include?