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Flat Roof Installation Cost

Flat Roof Installation Cost

National average
$4,000 - $5,000
(1200 sq.ft. home - modified bitumen)
Low: $1,000 - $2,000

(DIY - built-up)

High: $6,000 - $7,000

(rubber membrane & extra underlayment)

Cost to have flat roof installed varies greatly by region (and even by zip code).
Get free estimates from roofers in your city.

How much does it cost to have flat roof installed?

Flat roofs are simpler than pitched roofs, but still provide a variety of roofing options. The cost to install or replace a flat roof depends on size of the home and the material used, but the average cost for a modified bitumen roof for a 1200 square foot home is $4800.

Cost breakdown

  • Materials: there are three main types of flat roofs:
    • Built-up roof is the traditional flat roof made of layers of tar and gravel. The pros are that it is fire retardant and creates a nice view, but the cons are that is heavy and can require additional support beams, as well as being messy to install. It costs $0.50-$0.70 per square foot.
    • Modified bitumen 1 flat roofs are made with a roll peel-and-stick system ingrained with minerals. It is fairly easy to install and can help lower energy bills, but it is not as durable as other flat roofs. It averages $2 per square foot.
    • Rubber membrane roofs are made of a rubber that looks like an inner tube. Pros include that it is durable, light, and easy to install and repair, but the cons are that its dark color makes it hot and can add to energy bills. It costs $2-$3 per square foot.
  • Labor: most roofers will charge $2-$3 per square foot and expect a standard roof project to take two to three days to complete, or 16 to 24 hours of work.

Enhancement and improvement costs

  • Built-up roofs typically have three to five layers of tar and gravel. Adding additional layers can make the roof more durable but will increase your cost by $590-$750 per layer for a 1200 square foot, single story home.
  • Extra underlayment 2 can be added to the plywood 3 before the roofing material is installed to block water and other elements from entering the roof. The average cost is $0.40 per square foot.
  • Roof sealant is another option for preventing future leaks. This typically costs $850-$1000 for a standard roof.

Additional considerations and costs

  • Underlayment 2 is a waterproofing membrane always recommended to prevent the ingress of moisture and other elements. It also provides weather-proofing until the roof is installed. It is required depending on the type of roofing material and slope. Check local codes for requirements.
  • Different types of flat roofs perform better in certain climates. Talk to a roofing professional to find which type of roof is best in your area.
  • Installing or replacing a roof may require a permit or approval from your homeowners asociation (HOA). Talk to a roofing contractor about the specifics in your area.
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Remodeling Terms Cheat Sheet

Definitions in laymen's terms, cost considerations, pictures and things you need to know.
See full cheat sheet.
glossary term picture Bitumen 1 Bitumen: A viscous, black mixture of hydrocarbons often used for roofing and waterproofing. It is also used in asphalt for paving roads
2 Underlayment: Roofing material laid underneath roofing tiles to seal the roof, preventing leaks
glossary term picture Plywood 3 Plywood: An engineered construction material manufactured from thin slices of wood glued together in alternating grain patterns for strength

Cost to have flat roof installed varies greatly by region (and even by zip code). To get free estimates from local contractors, please indicate yours.

Labor cost by city and zip code

Compared to national average
Alameda, CA
Anniston, AL
Athens, GA
Atlanta, GA
Austin, TX
Baltimore, MD
Birmingham, AL
Brighton, MA
Bronx, NY
Brunswick, OH
Buffalo, NY
Chicago, IL
Columbia, MD
Detroit, MI
El Cajon, CA
Fort Lauderdale, FL
Fresno, CA
Garden Grove, CA
Griffin, GA
Hayward, CA
Henderson, NV
Holyoke, MA
Houston, TX
Jacksonville, FL
Kissimmee, FL
Lancaster, CA
Lanham, MD
Las Vegas, NV
Los Angeles, CA
Madera, CA
Miami, FL
Mobile, AL
Naples, FL
New York, NY
Nixa, MO
Ocala, FL
Orlando, FL
Philadelphia, PA
Phoenix, AZ
Pinole, CA
Port Saint Lucie, FL
Pueblo, CO
Riverside, CA
Rogers, AR
Sacramento, CA
Saint Louis, MO
San Antonio, TX
San Diego, CA
San Francisco, CA
San Jose, CA
Labor cost in your zip code
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Methodology and sources