Flat roofs are not flat. They’re just pitched—or angled—at a low slope of 10 degrees or less. Because they offer homeowners a durable and affordable roofing option, flat roofs are growing in popularity. They’re inexpensive to install and easy to maintain.
If your roof gets damaged, patching or replacing it can save your belongings and improve your home’s energy efficiency. When it comes time to replace a flat roof, the average cost can run between $3,000 and $10,000. There’s less area to cover compared to a standard sloped roof, so you can see big savings.
What Is a Flat Roof?
Flat roofs are roofs that are pitched at 10 degrees or less. They are typically composed of a single layer of waterproof material, often made up of a deck board with felt and adhesive layers, but sometimes made from a sheet of metal. These roofs may be called single-ply or single-layer roofs.
Generally, 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 20 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.
Cost of Flat Roof Replacement
Flat roof replacement cost varies based on the material the homeowner chooses. The average cost of flat roof materials and labor is between $4 and $13* per square foot.
Here’s a breakdown of average flat roofing costs per square foot:
| Flat Roof Material | Cost Per Square Foot |
|---|---|
| Metal Flat | $4–$30 |
| Modified Bitumen | $4–$8 |
| Built-Up (BUR) | $4–$10 |
| Rubber Membrane | $4–$13 |
| Single-Ply Membrane | $4–$7 |
| Thermoplastic Polyolefin (TPO) | $3.50–$14 |
| Fiberglass or GRP | $4–$6 |
*Cost figures in this article were sourced from HomeAdvisor and internal data.
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 flat roof replacement project can cost anywhere from $4–$30 per square foot. Costs vary based on factors such as your location, the size of your roof, and the type of metal roofing you choose.
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. These roofs generally cost $4–$8 per square foot installed. 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 an asphaltic rolled 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 you use and the size of the project. In general, this roof runs from $4–$7 per square foot.
Thermoplastic Polyolefin (TPO) Roof
Thermoplastic polyolefin roofing is a synthetic material. It’s 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–$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.
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. Additional roofing layers may run $1–$2 per square foot. Some roofers charge by the hour instead of the square foot—commonly $40–$80 per hour.
Material Types
The material you choose for your roof will have a major impact on the total cost. Asphalt, metal, tile, and composite shingles are the most common materials. 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, and any structural changes to your home, including roofing.
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. It can vary depending on whether or not you’re going through a contractor or doing it yourself.
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 are in line with relevant building codes. The average price for a permit is around $75, and an inspection can run from $100–$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 you have removed the old roofing material and replaced it, 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.
Vent Installation
Roof vents allow the flow of air and rainwater to escape from the roof, which is why they need to be replaced or installed if they are missing. Venting also reduces the amount of water that soaks into the roof over time. Ventilation generally costs $300–$600.
Professional vs. DIY
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 often 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:
- A knowledgeable team member inspects your roof before installation begins. They can provide an accurate estimate of the job’s cost.
- On the day work begins, roofers prepare the property. They typically spread tarps to protect flower beds and shrubs.
- Roofers remove old felt and the shingle roof.
- The team inspects your roof’s decking for any rotten wood or other structural problems.
- Roofers prepare the roof’s surface, installing a drip edge to prevent rain from seeping under your new shingles.
- 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.
- Roofers clean up the site and inspect their work.
DIY Flat Roof Replacement
Unless you are a roofer by trade and training, you cannot replace your own roof. 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 more difficult to insulate and waterproof. That’s why you want it done right. If you’re replacing your flat roof, hire a professional for the job.
Top Cities for Flat Roofs
We’ve researched and vetted roofing companies state and country-wide. Find top-recommended roofers near you in our guides below.
Our Conclusion
Homeowners with a flat roof should budget up to $13,000 for the total cost of flat roof replacement. 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 at least three local roofing contractors before deciding.
FAQ About Flat Roof Replacement
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