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    Home | Our Blog | Flat Roof Installation or Replacement Cost

    Flat Roof Installation or Replacement Cost

    Reviewed by Tomas Kalkys. President.
    Qualifications: More than 20 years of experience in residential and commercial exterior remodeling.
    Founding farther of Legacy Service.
    Written by LegacyUSA Team

    posted on May 7, 2022

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    Cost of Flat Roof Replacement

    Is it time to replace your flat roof? It’s important to get an idea of the potential cost before you get started.

    Demand for flat roofs has increased over the past few years due to their distinctly modern look along with how easy they are to install and repair. Our team of professionals here at Legacy Service provides installation and replacement services for homeowners throughout southeastern PA, NJ, and DE.

    In this article, we’ll discuss the price ranges of flat roof replacement for the different types of materials. If you’re interested in receiving a free consultation, get in touch with our team today at 215-798-9790 or

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    What is a Flat Roof?

    Flat roofs may not be as common as other types of materials like asphalt shingles, but they can often be found on certain styles of homes. They’re characterized by having little to no pitch or slope. Since this may allow water to puddle, these roofs must be covered with a special type of material. In this blog, we’ll discuss the flat roof replacement cost for the various materials.

    Flat Roof Replacement Cost Per Square Foot

    It’s important to note that the cost of flat roof replacement will differ from project to project depending on a variety of factors, but you can still get an idea of the cost beforehand.

    In 2022, property owners can expect to pay about $4 to $30 per square foot for the installation, including both materials and labor.

    Commercial Flat Roof Replacement Cost Per Square Foot

    Depending on the material, commercial flat roofs typically cost between $4 and $9 per square foot to install. Most of them are much bigger than residential roofs, with 10,000 square feet being the average. Owners of commercial buildings can expect to pay between $40,000 and $90,000 for their flat roof depending on the material type as well as the need for drains, vents, and extra underlayment.

    New Flat Roof Costs

    The price typically depends on the material you choose. Common materials include EPDM, rubber, fiberglass, GRP, modified bitumen, and built-up tar. Once you’ve chosen the material, you’ll also have to factor the cost of labor into the total price. The roofing contractor you work with will be able to provide you with the costs before beginning the project.

    New Roof or Replacement Cost

    Whether you need a completely new roof or a replacement, you’ll have to pay for both the material chosen as well as the labor completed. However, the price may differ depending on what you need. In the sections below, we’ll discuss the average estimated cost of installation vs. replacement.

    Flat Roof Installation Cost

    Installation is the process of installing a new roof on your residential or commercial property, without having to tear off an old one. Depending on the size and complexity of your home, the cost of labor for installation can start at $5 to $5.50 per square foot and can go up to $7 to $9 per square foot. Keep in mind that it may differ depending on the material and contractor you choose.

    Cost to Replace a Flat Roof

    If you’re replacing your roof, in most cases, you’ll need to remove the old one. This may add to the cost of labor, but it will be worth it in the long run when it’s installed properly. Flat roof replacement cost per square foot will typically range between $4 to $9.

    Flat Roof Materials

    Flat Roof Materials

    You have plenty of options to choose from when it comes to flat roofing materials. The most common ones used for residential and commercial buildings in the United States include fiberglass, rubber, EPDM, PVC, TPO, rolled roofing, built-up tar, GRP, modified bitumen, spray foam, and metal.


    Fiberglass is a popular material because it’s low cost and highly resistant to water. It usually lasts between 25-50 years, and in most cases, homeowners can expect to pay about $4 to $6 per square foot.


    Rubber can be more expensive than other materials, but it tends to be worth it in the long run. It’s lightweight, resistant to sun damage, and designed to last up to 50 years with the proper care. It typically costs about $4 to $13 per square foot.


    EPDM (Ethylene Propylene Diene Monomer) is a durable and inexpensive material. It’s also quite easy to install. Its lifespan usually ranges from between 10-15 years, and it can cost anywhere between $5 to $13 per square foot.


    PVC (Polyvinyl Chloride) is one of the most common flat roof materials in the United States. PVC, along with EPDM and TPO, are all single-ply membranes, so installation and repair can be quite simple. PVC roofs can last 30-50 years and may cost $6.50 to $7.50 per square foot.


    TPO (Thermoplastic Polyolefin) is another single-ply membrane. After EPDM, it’s the second-most commonly used material on residential flat roofs. It’s popular because it can both weatherproof the roof and reflect heat. It’s known to last 20-30 years and typically costs $6 to $7 per square foot.

    Rolled roofing

    Rolled roofing is ideal for sheds, garages, and porch roofs. It’s actually produced from the material used in asphalt shingles. This material has a lifespan of 8 to 12 years, and its price can range between $5.50 to $6.50 per square foot.

    Built-up tar

    A built-up tar roof features several layers, and it’s typically used on flat roofs with a very slight pitch. Property owners choose them because they’re inexpensive and designed to be fireproof. They have a lifespan of about 20-30 years, and they tend to cost anywhere between $4 and $10 per square foot.


    GRP (Glass Reinforced Polyester) features a blend of fiberglass and plastic that helps withstand the elements. This material usually has a lifespan of about 25 to 50 years, and homeowners can expect to pay $4 to $6 per square foot for materials and labor.

    Modified bitumen

    Modified bitumen is rolled out onto the roof, and then a blowtorch is used to secure the material. Once installed, this material reflects heat well. It’s also quite affordable, usually costing between $4 and $8 per square foot. Its lifespan is about 10-15 years.

    Spray foam

    Spray Polyurethane Foam (SPF) is a liquid that’s sprayed on the existing roof and expands into foam, which creates a solid layer across the roof. This roofing material can last 15 to 20 years, and it has an average price range of $4 to $7 per square foot.


    Metal roofs can last for decades if they’re well-maintained, and they can also reduce cooling costs during the warm summer months. Zinc is a popular choice because it can last between 60 to 100 years in the right climates. Costs for metal can range from $4 to $30 per square foot.

    Flat Roof Installation Cost by Type 

    Flat Roof Installation Cost by Type

    The type of flat roof will also affect the cost of installation. The most common types include cold, warm, inverted, hybrid, curved, tapered, and green. In the sections below, we’ll review the pros and cons, characteristics, and average costs of each. It’s good to get an idea of the average cost for flat roof replacement no matter which type you choose.


    Cold flat roof design places the insulation under or between the rafters, which leaves the roof and timbers cold. This is a great option due to ease of installation, low impact, and cost-effectiveness. However, they can be tricky to install on existing roofs. The average price for cold roofs can range between $4 and $9 per square foot.


    Warm roof design places the insulation above the joists and deck, which allows the roof and loft to have a similar temperature to the one inside the building. They have many advantages including their cost-effectiveness, thermal efficiency, ease of installation, the fact that they allow moisture to escape, and their ability to eliminate cold bridging. Property owners can typically expect to pay between $6 to $11 per square foot.


    With inverted roofs, the waterproofing layer lies beneath the insulation rather than above it. This helps keep the roof warm during the winter months and at a milder temperature during the warmer months. They resist water absorption, protect against UV rays, and provide excellent thermal performance. They tend to cost about $4 to $9 per square foot.


    Hybrid roofs, also called compact roofs, combine the elements of cold and warm roof construction. Most of the insulation is placed between the rafters. While they can be difficult to install, they provide maximum thermal performance and still minimize the thickness of the roof. The price usually ranges between $4 and $11 per square foot.


    Curved roofs consist of a single gable where one side has little slope and the other side slopes down. Not only do they help shed snow and rainwater, but they also provide charm to any building. While they can be more expensive than other types, they require less framework and help reduce the emission of CO2 gases. Their price typically ranges between $8 to $15 per square foot.


    With tapered roofing systems, the slope of the roof is formed by the insulation. It still has the benefits of a flat roof, but the slope helps drain excess debris and water, which helps extend your roof’s lifespan. It’s also a lightweight material that’s quick to install. Property owners can expect to pay between $7 and $10 per square foot.


    Green roofs can be the most expensive type of flat roof to install, but they can also be worth it in the long run. They’re a great way to manage stormwater runoff and insulate your home. Compared to other types of flat roofs, they have an improved drainage system, thermal performance, and increased lifespan. Costs will normally range between $10 and $35 per square foot.

    Flat Roof Extension Cost

    An extension can be done for many reasons, including homeowners who want to add or expand their kitchen, office, bedroom, or another area of their home. The cost will vary depending on the size of the extension. However, most homeowners can expect to pay somewhere between $1,000 and $20,000.

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    Additional Tool and Material Costs to Install a Flat Roof

    If you’re considering DIY flat roof replacement, you’ll also need to include the costs of additional tools and materials needed for the job in your budget. These costs will depend on what you already have and what you need. Some basic tools you’ll need include a roofing hammer, roofing nailer, utility knife, roof cleaning equipment, moisture detection tools, and more.

    DIY Flat Roof Replacement vs. Hire a Pro

    Unless you have the experience, tools, and time to get the job done right, it’s best to hire a team of professionals for flat roofing replacement or installation. They’ll be able to open up your roof without causing damage, and they’ll also lay down the new roof so that you don’t have to worry about leaks in the future.

    What are the advantages and disadvantages of a flat roof?

    Flat roofs have increased in popularity over recent years for many reasons. Their modern appeal complements a broad range of home designs, and according to Energy Star, they even have better energy efficiency than traditional pitched roofs. However, they also have their downsides. Low-grade slopes may slow drainage, which can lead to ice dams and pools of water. They also will not work on every type of home.

    In most cases, you’ll know whether you need a flat roof or not. You can also schedule a consultation with an expert to get their opinion.

    How Much Does a Flat Roof Cost?

    As you know by now, the cost will depend on a variety of factors. The most notable ones include the cost of materials, labor, accessories/tools, and the size and shape of your roof. If you want a personalized flat roof replacement estimate, get in touch with a local roofing contractor.

    Average cost of materials

    While the price may vary from material to material, most will typically cost between $1 and $4 per square foot (not including labor). EPDM and modified bitumen average at about $2 to $4 per square foot, while GRP and fiberglass are usually the cheapest at about $1 per square foot.

    Average cost of labor

    Property owners can expect labor to cost about $3 to $7 per square foot for installation (including the removal and disposal of the old roof). For additional roofing layers, expect to pay about $1 to $2 per square foot.

    Cost of accessories/tools

    For flat roof replacement DIY, you’ll also need to include the cost of accessories and tools into your budget. This will depend on what you already have and what you need. Doing it yourself isn’t recommended unless you have the proper time, experience, and tools to do the job right.

    Cost of Flat Roof Replacement

    FAQ: Cost of Flat Roof Replacement

    Sometimes, just asking, “How much is a flat roof replacement?” won’t give you the answers you’ve been looking for. Here are more specific questions that we’re most frequently asked about flat roof replacement.

    Are flat roofs expensive?

    Flat roofs are one of the more affordable roofing types. Installation tends to be quicker and easier, and fewer materials are required. Also, flat roof materials come in large rolls compared to pitched roof materials, which come in small sheets.

    How much does it cost to replace a flat roof per sq.ft.?

    The cost to replace a flat roof depends on the material chosen as well as the size and shape of the roof. The average cost is usually between $4 to $30 per square foot.

    What is the best material for a flat roof?

    The best material for a flat roof depends on your preferences and needs. For example: If you live in a colder climate, you’ll want to search for the best flat roof replacement material in cold temperatures. Get in touch with a local contractor to schedule a consultation and find out which one would work best for you.

    How do you maintain a flat roof?

    The good news is that flat roofs are fairly easy to maintain. They should be inspected annually, checked for cracks, and sealed as needed. Sealant helps keep the rest of your roof easy to maintain. Also, remember to inspect and clean your gutters every six months or after a big storm.

    How to choose the right flat roof?

    When choosing a flat roof, it’s best to consult with a professional to see which one they would recommend for you. Some materials do better in certain climates than others.

    How long will a flat roof last?

    Flat roofs have various lifespans depending on the type of material chosen. Rubber roofs can last up to 50 years with the proper care, while rolled asphalt may only last about 8-12 years. Homeowners can expect most to last somewhere between 10-50 years.

    How often should you coat a flat roof?

    Your flat roof should be inspected annually, but it should only be coated as needed. In general, it will not need to be coated unless you notice cracks.

    Can flat roofs be repaired?

    Yes, flat roofs can be repaired. If you notice leaks or cracks in your roof, you can have it sealed to prevent water damage. Remember to have your roof inspected regularly for cracks, holes, or tears. If you have the experience, tools, and time, you can do the repair yourself. Otherwise, it’s best to hire professionals.

    Is it safe to stand on a flat roof?

    It’s always risky to stand on a roof, no matter which type it is. While flat roofs are designed to be completely safe to stand on after they’ve been properly sealed and treated, you should always have the roof inspected before standing on it.

    Get Started on Your Flat Roof Replacement!

    Now that you have a good understanding of flat roof costs, it’s time to get started on your own project. At Legacy Service, we provide roofing installation and replacement services to homeowners throughout southeastern Pennsylvania, New Jersey, and Delaware.

    Call us at 215-798-9790 to schedule a free consultation.

    Find qualified roofers near you

    Posted on May 7, 2022 in Roof

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