Replacement Cost of Flat Roof

Flat roofs may appear to be completely level, but they are slightly pitched or angled at a low slope, typically around 10 degrees. Despite their name, flat roofs are gaining popularity among homeowners due to their affordability and durability. They offer a cost-effective and long-lasting roofing option. Additionally, installing flat roofs is a budget-friendly choice, and they require minimal maintenance. However, flat roof replacement cost can vary depending on several factors. 

In the event of roof damage, it is crucial to promptly address the issue to safeguard your belongings and enhance the energy efficiency of your home. The cost to replace a flat roof can vary between $3,000 and $10,000 on average. Opting for a flat roof instead of a sloping one can lead to significant savings in terms of expenses.

What Is a Flat Roof?

Roofs with a pitch of 10 degrees or less are considered flat roofs. Flat roofs are typically constructed with a single layer of waterproof material, which can include felt, deck boards, or metal sheets. They are often referred to as single-ply roofs or single-layer roofing.

Compared to other types of roofs, flat roofs can be more cost-effective to install and repair. Additionally, their replacement or repair costs are generally lower due to their usage of fewer materials. Therefore, it is not necessary to devote excessive time to intricate architectural details.

Flat roofs can also contribute to energy efficiency by effectively insulating homes during winter and providing a cooling effect in warmer climates. Moreover, they offer versatility, as some homeowners utilize them for rooftop gardens.

However, it is important to note that flat roofs typically have a shorter lifespan compared to sloped roofs. While asphalt roof shingles, the most commonly used material for sloped roofs, can last up to 20 years, they are not suitable for flat roofs due to inadequate water drainage. The lifespan of a flat roof generally ranges from 10 to 15 years, depending on the materials used. Nonetheless, certain flat roofing materials have the potential to last for several decades.

Cost of Flat Roof Replacement

The cost of replacing a flat roof depends on the type of material selected by the homeowner. The cost of materials and labor for flat roofs typically ranges between $4 to $13 per square foot. 

Here is a breakdown of the average cost per square foot for flat roofs:

Flat Roof MaterialCost 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$3.50-$14
Fiberglass or GRP$4-$6

Metal Flat Roof

Metal roofs are popular due to their beauty, durability, and versatility. They can withstand harsh weather conditions such as high winds and hail.

The cost of a flat roof replacement can range from $4 to $30 per square foot. The cost of metal roofing varies depending on factors such as your location, roof size, and the type of metal you choose.

Modified Bitumen Roof

Since 1975, modified bitumen has been an asphalt-based roofing material designed for roofs with low slopes. It is resistant to environmental pressures and has high tensile strength, meaning it won’t break under tension.

Modified bitumen roofing typically consists of five layers: insulation, modified base sheets, modified bitumen membranes, adhesive, and surfacing. The cost of these roofs generally ranges from $4 to $8 per square foot. If an existing roof needs to be removed, the cost will be higher.

Built-Up Roofs (BUR)

BUR (Built-Up Roofing) is a great option for roof replacements that are easy to maintain and can last for many years. BUR is also known as gravel-and-tar roofs. It is a type of roofing that consists of multiple layers of asphalt and felt. The average cost per square foot for BUR ranges from $4 to $10.

Rubber Membrane Roof

EPDM rubber (ethylene propylene diene monomer) is one of the most affordable roofing materials available. Rubber is highly durable, with a potential lifespan of up to 50 years, making it a preferred choice for many homeowners. Rubber roofing is resistant to hail, heavy snow, and wind, unlike other types of flat roofs. On average, the cost of an EPDM rubber roof membrane ranges between $4 and $13 per square foot.

Single-Ply Membrane Roofing

A single-ply roofing membrane is a rolled asphaltic roof system that can be installed as a single piece and used in conjunction with various underlays. These roofs have a potential lifespan of up to 40 years and offer several advantages. Some brands even claim to be waterproof and termite resistant.

The cost per square foot depends on the type of materials used and the size of the project. Typically, this type of roof costs between $4 and $7 per square foot.

Thermoplastic Polyolefin Roof

Thermoplastic Polyolefin (TPO) is a synthetic roofing material that is highly favored by commercial buildings due to its watertight nature and long lifespan lasting for decades. It is lightweight and easy to install, requiring minimal maintenance. The cost of TPO roofs typically ranges from $3 to $14 per square foot, encompassing both materials and labor expenses.

GRP or Fiberglass Roof

Fiberglass is a type of plastic reinforced with fibers. It is lightweight, durable, and fire-resistant. It is typically less expensive than other decorative materials such as tile. The average cost is around $6 per square foot.

Glass-reinforced-plastic (GRP) polymer is a fiber-reinforced polymer that offers resistance against cracking, ice dams, mold, and mildew. If you’re looking for a roofing material that resembles shingles or tiles, GRP is a good option. It is slightly more expensive than fiberglass but still an affordable choice.

Factors That Impact Flat Roof Replacement Costs

The material and size of your flat roof are important factors in determining the cost of a new roof.

Drainage System

Drainage systems on flat roofs ensure proper water drainage. This system may need to be replaced when the roof is being replaced. The cost to replace a drainage system varies depending on its type and the extent of repairs needed. Prices typically range from $600 to $1,000. Before starting the replacement, it is important to identify any damage and blockages. It is recommended to hire a professional for the job.

Labor Costs

For flat roof installation, homeowners can expect to spend $3 to $7 per square foot. The cost of additional roofing layers can range from $1 to $2 per square foot. It is worth noting that some roofers charge by the hour instead of the square foot.

Material Types

The type of material you select for your roof can greatly affect its cost. Asphalt shingles, metal tiles, and composite shingles are among the most popular choices. Each material has its advantages and disadvantages, but they are all of high quality. If necessary, budget-friendly options like tar paper and aluminum sheets can also be considered.

Permits and Inspections

The requirement for a permit to replace your roof depends on the municipality where you reside. Permits are typically necessary for any electrical, plumbing, or structural work conducted on your home.

Permits can significantly impact both the timeline and cost of your project. The cost of permits can vary widely based on factors such as project location, size, and complexity. Additionally, the cost may differ depending on whether you hire a contractor or choose to do the work yourself.

To obtain a permit, either you or your contractor will need to contact the city or county office. This is also an opportunity to ensure that your plans comply with relevant building codes. Permit costs typically range around $75, while inspection fees can range from $100 to $600.

Roof Removal

The first step in any roofing project is removing the old roof. While it may be tempting to do it yourself, hiring a professional is generally considered safer and easier. Roofers typically include the cost of a “tear-off” in their labor charges, which usually range between $3 and $7 per square foot.

Roof Sealant

Installers should seal your new roof after removing the old material. This step is crucial for protecting it against climate damage. Sealants enhance the shingle’s permeability and prevent moisture leakage.

The cost of a typical sealant can range from $50 to $1,000, depending on factors such as whether the roofers are sealing skylights, chimneys, or other areas. The cost of sealing flat roofs is generally lower since they do not require steep slopes.

Vent Installation

Roof vents are essential for facilitating air flow and allowing rainwater to escape from the roof. They should be installed or replaced if they are missing. Proper ventilation also helps to minimize the amount of water absorbed by the roof. The cost of ventilation typically ranges from $300 to $660.

Professionals vs. Do-It-Yourself

Roofs should not be taken lightly, as they require expertise and caution. Do-it-yourself roofing can be dangerous and there is a risk of damaging your house. Regardless of the size or complexity of the roof, it is strongly recommended to hire a roofing professional for assistance with the roofing project.

Professional Flat Roof Installation

To replace your flat roof, it is advisable to hire a professional contractor or roofing company. Attempting to complete this project on your own may pose safety risks. Flat roofing materials are typically heavy and require proper fastening with screws, nails, and sealant. Depending on the specific roofing material used, an installer may also need to apply a sealant or coating.

Contractors often offer warranties for the installation cost, ensuring that you are not responsible for repair expenses if issues arise.

When you hire a professional roofer, they generally follow a similar process:

  1. Before the installation process begins, a team member inspects your roof to provide an accurate cost estimate.
  2. On the day before starting the work, roofers typically prepare their property by spreading tarps over flower beds and shrubs.
  3. The roofers proceed to remove the old felt and shingles from the roof.
  4. During the process, the team will inspect the roof decking to identify any structural issues or rotten wood.
  5. To prevent rain from seeping underneath the new shingles, roofers install a drip edge.
  6. Next, the new roofing materials are installed, and new underlays are laid down. The process is usually completed by applying a sealant, such as ethylene, to the roof.
  7. Once the installation is finished, roofers inspect and clean the worksite to ensure its proper condition.

DIY Flat Roof Replacement

You should not attempt to replace your roof unless you are a trained and licensed roofer. It is crucial to hire a contractor with experience in installing and sealing flat roofs for replacement.

Flat roofs are more prone to water leakage and damage compared to other roof types. They also present additional challenges in terms of waterproofing and insulation. To ensure the job is done correctly, it is highly recommended to hire a professional to replace your flat roof.


Budget up to $13,000 in total for a flat roof replacement. Although this price is generally lower than that of a typical roof, it is important to note that many flat roofs have a shorter lifespan. Opting for a durable material like rubber or metal may result in a higher cost initially, but it will also provide a longer-lasting roof.

Need a Cost Estimate for Your Flat Roof Replacement? Call All Star Roofing!

In need of a cost estimate for your flat roof replacement? All Star Roofing is the solution you’ve been searching for! Our team of experts is ready to provide you with a detailed and competitive pricing proposal customized to meet your specific requirements. 

We cater to both homeowners and business owners, recognizing the significance of a well-maintained roof. With our unwavering commitment to delivering exceptional service, you can trust us to handle your flat roof replacement needs with utmost professionalism. 

Contact us today and allow us to prioritize your satisfaction!

FAQs About Flat Roof Replacement

Is It Cheaper to Replace a Flat Roof?

Because they cover less surface area, flat roofs generally have lower replacement costs compared to roofs with a slant. Roofs with a slant typically require additional materials, resulting in higher costs. Flat roofs are commonly chosen for houses as a cost-saving measure for both installation and maintenance.

How Long Does a Flat Roof Usually Last?

The materials and maintenance of a flat roof will determine how long it lasts. Modified bitumen or built-up roofing can last 10-20 years. Thermoplastic polyolefin, spray-on polyurethane, acrylic or silicone coatings, and thermoplastic polyolefin may also provide durability.

What Is the Cost of Installing a Pitched Roof Over a Flat Roof?

A pitched roof of average size will cost at least $30,000 on a flat surface. It can be challenging to estimate the cost for this project as prices will vary widely depending on the region, season, and current material prices.

How Often Should a Flat Roof Be Coated?

A flat roof should be recoated every five years. Unmaintained flat roofing will last about 10 years. Coating it will ensure that it remains in good condition for as long as it is needed.

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