Because they offer homeowners a durable and affordable roofing option, flat roofs are growing in popularity. If your flat roof gets damaged beyond repair and you need to replace it, the average cost of materials and labor is between $4 and $13 per square foot. The typical total cost range of a flat roof installation is between $4,800 and $15,600 for a 1,200-square-foot roof with an average cost of $9,400.* The cost varies based on the roofing material the homeowner chooses, but since there’s less area to cover compared to a standard sloped roof, you can see big savings.

*Cost figures in this article were sourced from HomeAdvisor and internal data.

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What Is a Flat Roof?

Flat roofs are pitched at 10 degrees or less. They are typically composed of a single layer of waterproof material, often a deck board with felt and adhesive layers, but sometimes a sheet of metal. These roofs may be called single-ply or single-layer roofs.

Generally, the different types of flat roofs are cheaper to install than other types of roofs and may cost less to repair or replace because fewer materials are involved. You won’t need to spend hours working with complex architectural details.

Flat roofs are energy efficient, keeping homes warm in the cold months and cooler in warm climates. Some homeowners enjoy the versatility of flat roofs and use the space to plant rooftop gardens.

Flat roofs usually don’t last as long as their sloped cousins, however. Asphalt shingles are the most popular material for sloped roofs and last up to 50 years. Flat roofs can’t be built with asphalt shingles, though, because water does not drain off them properly. Depending on the material, flat roofs typically last just 10–15 years, although some flat roof materials can last for decades.

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What Does Flat Roof Replacement Cost by Size and Type?

Here’s a breakdown of average flat roofing costs per square foot:

Flat Roof Material	Cost Per Square Foot*	Total Cost
Metal Flat	$4–$30	$4,800–$36,000
Modified Bitumen	$4–$8	$4,800–$9,600
Built-Up (BUR)	$4–$10	$4,800–$12,000
Rubber Membrane	$4–$13	$4,800–$15,600
Single-Ply Membrane	$4–$7	$4,800–$8,400
Thermoplastic Polyolefin (TPO)	$3.50–$14	$5,950–$16,800
Fiberglass or GRP	$4–$6	$4,800–$7,200

Metal Flat Roof

Many people love metal roofs because they’re versatile, beautiful, and long-lasting. They can withstand extreme weather conditions such as high winds and hail. 

An average metal flat roof replacement project can cost between $4 and $30 per square foot. Costs vary depending on factors such as location, roof size, and metal roofing type.

Modified Bitumen Roof

Modified bitumen, an asphalt-based roof material designed for low-sloped roofs, has been used in the United States since 1975. It can withstand heavy environmental pressure and has a high tensile strength, meaning it won’t break easily under tension.

Modified bitumen roofs consist of five layers: insulation, modified base sheets, modified bitumen membranes, adhesive, and surfacing. They generally cost $4–$8 per square foot installed, and it will cost more if an existing roof needs to be removed.

Built-Up Roof (BUR)

If you’re looking for a cost-effective roof replacement that’s easy to maintain and lasts for years, built-up roofing (BUR) may be the right solution. BUR, also known as gravel-and-tar roofing, is a type of roofing made from multiple layers of felt and asphalt. This material has an average cost of $4–$10 per square foot.

Rubber Membrane Roof

EPDM (ethylene propylene diene monomer) rubber is one of the most affordable roofing materials. It’s so durable that it can last up to 50 years—which is probably why many homeowners choose it. Rubber roofing can withstand hail, wind, and heavy snow, unlike other flat roof materials. The cost of a rubber membrane roof ranges from $4–$13 per square foot on average.

Single-Ply Membrane Roof

Single-Ply membrane is a roofing system installed in one piece. It can be used with a variety of underlayments. A single-ply membrane roof can last up to 40 years and has many benefits. Some brands advertise that it is waterproof and termite-resistant. 

The cost per square foot depends on the type of material used and the size of the project. In general, this roof costs $4–$7 per square foot.

Thermoplastic Polyolefin (TPO) Roof

Thermoplastic polyolefin roofing is a synthetic material popular for commercial buildings because it is watertight and can last for decades. It is easy and lightweight to install and doesn’t require much maintenance. The average cost per square foot of TPO roofing ranges from $3 to $14, including materials and labor.

Fiberglass or GRP Roof

A type of fiber-reinforced plastic, fiberglass is lightweight, durable, and fire-resistant. It is typically less expensive than decorative materials such as slate or tile. On average, it costs between $4–$6 per square foot.

Glass-reinforced plastic (GRP) is a fiber-reinforced polymer that resists cracking and ice dams and prevents mold and mildew growth. It’s a great option if you want something that looks like a traditional shingle or tile. It’s only slightly more expensive than fiberglass.

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How to Calculate the Replacement Cost of Your Flat Roof

1. Take the square footage of your home

2. Since a flat roof has no pitch, the roof square footage will be in line with the square footage of your home.

3. Multiply this number by the average cost per square foot of a flat roof of $6

4. This gives you an estimated cost of what you would pay for a new flat roof

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What Are Factors That Impact Flat Roof Replacement Costs?

Knowing the material and size of your roof is a great start to understanding how much your roof replacement will cost, but several other factors also affect your new flat roof estimate.

Drainage System

On flat roofs, drainage systems ensure that water drains properly. When replacing the roof, this system may also need replacing. The cost of replacing a drainage system can vary depending on the type of system and the extent of repair needed. In general, prices run from $600–$1,000. You will want to identify any damage or blockages before you start. It’s recommended to hire a professional for the job.

Labor Costs

Homeowners can expect to pay $3–$7 per square foot in labor costs for flat roof installation. The cost of roof repair may run $1–$2 per square foot for additional roofing layers. Roofers generally charge by the hour instead of the square foot—commonly $40–$80 per hour.

Material Types

The material chosen for your roof will have a major impact on the total cost. Asphalt, metal, tile, and composite shingles are the most common roofing materials, though not all fit on flat roofs. Each type has benefits and drawbacks, but they all perform well in terms of quality. Budget-friendly options such as tar paper or aluminum sheets can be used if needed.

Permits and Inspections

Whether you need a permit or an inspection to replace your flat roof depends on the municipality you live in. In some areas, you need to get permits for electrical work, plumbing work, roofing, and any structural changes to your home.

Permits can have a huge impact on the cost and timeline of your roof replacement project. The cost of permits varies widely based on the project’s location, size, and complexity.

To obtain a permit, you or your contractor must contact your city or county offices. This is a good time to make sure your plans comply with relevant building codes. The average price for a permit is around $75, and an inspection can run from $100 to $600.

Roof Removal

Removing the old roof is the first step in any roofing project. You may be tempted to do this yourself, but it’s safer and more convenient to hire a professional. A “tear-off,” as roofers call the job, is typically included in the labor costs at $3–$7 per square foot.

Roof Sealant

Once the old roofing material is removed and replaced, installers should seal the new roof to protect it from climate damage. Sealants also improve shingle permeability, preventing moisture from seeping through.

A typical sealant could cost anywhere from $50–$1,000, depending on whether you have chimneys, skylights, or other areas for the roofers to seal. Flat roofs run on the lower end of the price range because the laborers do not have to cope with a steep slope.

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How Does Flat Roofing Cost Compare to Other Types of Roofs?

Though there are many factors to consider when choosing a new roof, two of the most important are the overall cost and projected life span of each material. Gauging both of these factors can help you learn how metal roofing compares to other roofing material options.

Material	Cost per sq. ft	Total Cost*	Life span in Years
Asphalt Shingles	$4.25–$8.25	$5,100–$9,900	20–30
Built-up Roofing (BUR)	$3.42–$4.90	$4,104–$5,880	15–30
Clay Tiles	$5.90–$14.68	$7,080–$17,616	50–100
Concrete Roofing	$5.16–$8.60	$6,192–$10,320	50
Green Roofing	$10–$28	$12,000–$33,600	40
Metal Roofing	$9–$14.60	$10,800–$17,520	40–70
Slate Roofing	$7.56–$18.70	$9,072–$22,440	75–200
Solar Roofing	$16.10–$20.85	$19,320–$25,020	25–30**
Wood Shake	$6.53–$9.90	$7,836–$11,880	15–30

Your roof’s life span may vary depending on how well you maintain your flat roof and various weather and locational conditions. If not maintained properly, your roof may need replacement sooner rather than later.

Asphalt Shingles

Aluminum Shingles

Cedar Shingles or Shakes

Clay and Concrete Tiles

Copper Tiles

Flat Roofing Materials

Slate Tiles

Standing Seam Metal Panels

Steel Shingles

Zinc Tiles

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Professional vs. DIY Flat Roof Installation

Don’t take roofing lightly. DIYing a roof is a safety hazard. In addition to the danger of falling, you risk damaging your home. We recommend using professional help for all roofing projects, no matter the size or complexity of the roof.

Professional Flat Roof Installation

It’s important to hire a professional roofing company or contractor to replace your flat roof. It can be a difficult and dangerous home improvement project to complete on your own. The materials used for this kind of roofing are specialized, heavy, and need to be secured in place with nails, screws, and sealant. The installer may need to apply one of several types of coating or sealant, depending on the type of material you’re using for your roof.

One of the best reasons to hire a contractor is that they may offer you a warranty on the installation costs. If you have a warranty and something goes wrong with your new roof, you’re not responsible for paying to repair it.

When you contract with a professional roofer, they generally follow a standard process:

1. A knowledgeable team member inspects your roof before installation begins. They can provide an accurate estimate of the job’s cost.
2. On the day work begins, roofers prepare the property. They typically spread tarps to protect flower beds and shrubs.
3. Roofers remove the old felt and roofing material.
4. The team inspects your roof’s decking for any rotten wood or other structural problems.
5. Roofers prepare the roof’s surface, installing a drip edge to prevent rain from seeping under your new roofing.
6. The roofers lay the new underlays and install your new roofing materials. Typically, they finish with a sealant such as ethylene to coat the roofing system.
7. Roofers clean up the site and inspect their work.

DIY Flat Roof Replacement

Unless you are a roofer by trade and training, you cannot build a flat roof correctly. Replacing your flat roof requires a contractor who knows how to install and seal the roof properly.

Flat roofs are susceptible to leaks and water damage. They are also more difficult to insulate and waterproof, so you want them done right. If you’re replacing your flat roof, hire a professional for the job.

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Our Conclusion

Homeowners with a flat roof should budget up to $13,000 for the cost of a roof installation when replacing their flat roof. While this price runs less than the cost of a traditional roof, many flat roofs last only half as long. Using a more durable roofing material, such as metal or rubber, may raise the price, but it will substantially increase the roof’s life span.

Because so many factors influence flat roof replacement costs, we recommend getting estimates from three local roofing contractors, if possible, before deciding.

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FAQ About Flat Roof Replacement

Are flat roofs cheaper to replace?

Flat roofs are cheaper to replace because they have less area to cover. Slanted roofs require more building materials, thus costing more. Houses are more likely to be fitted with a flat roof to reduce installation and repair costs.

How long do flat roofs usually last?

How long a flat roof lasts depends on the materials used and maintenance performed. For example, a modified bitumen roof or a built-up roof can last for 10–20 years. Products such as thermoplastic polyolefin and spray-on coatings of polyurethane foam, acrylic, or silicone may be just as durable.

How much does it cost to put a pitched roof on a flat roof?

It will likely cost more than $30,000 to put an average-sized pitched roof on a flat roof. However, it can be tricky to judge the cost of this massive project. The price will vary widely depending on region, season, and current material prices.

How often should you coat a flat roof?

You should coat a flat roof every five years. While an unmaintained flat roof will typically last 10 years, coating it will help ensure it stays in good condition for as long as you need it.

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What Are the Top Cities for Flat Roofs?

We’ve researched and vetted roofing companies across the U.S. Find top-recommended roofers near you in our guides below.

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