FLAT ROOF REPLACEMENT: Costs and All You Need To Know


Flat roofs are not flat. They are simply 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 are inexpensive to install and simple to maintain. If your roof is damaged, patching or replacing it can save your possessions and improve the energy efficiency of your home. When it comes to flat roof replacement, the average cost can range between $3,000 and $10,000. You can save a lot of money because there is less area to cover than on a standard sloped roof. As a result, in this article, we’ll examine both the cost of a flat roof replacement and the various installation options.

What is a Flat Roof?

Flat roofs are roofs that are pitched at 10 degrees or less. They are typically made of a single layer of waterproof material, usually a deck board with felt and adhesive layers, but can also be made of a sheet of metal. These roofs are known as 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 have to spend hours working with intricate architectural details.
Flat roofs conserve energy, keeping homes warm in the winter and cool in the summer. Some homeowners appreciate flat roofs’ adaptability and use the space to grow rooftop gardens.

Cost of a Flat Roof Replacement

Flat roof replacement cost varies depending on the material chosen by the homeowner. Between $4 and $13 per square foot is the typical cost of flat roof materials and labor.

The following is a breakdown of typical flat roofing prices per square foot:

#1. Metal Flat Roof

Metal roofs are popular because they are versatile, beautiful, and long-lasting. They are resistant to harsh weather conditions such as high winds and hail.

Typically, a flat roof replacement project will cost between $4 and $30 per square foot. Your location, the size of your roof, and the type of metal roofing you select will all affect the cost.

#2. Modified Bitumen Roof

Since 1975, the United States has used modified bitumen, an asphalt-based roof material designed for low-sloped roofs. It can withstand high environmental pressure and has a high tensile strength, which means it won’t easily break under tension.

Modified bitumen roofs have 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 to remove an existing roof.

#3. Built-Up Roof (BUR) 

Built-up roofing (BUR) may be the best option if you’re looking for a cost-effective roof replacement that is simple to maintain and lasts for years. BUR, also known as gravel-and-tar roofing, is a type of roofing that is made up of several layers of felt and asphalt. This material typically costs between $4 and $10 per square foot.

Factors That Impact the cost of Flat Roof Replacement 

Knowing the material and size of your roof is a good place to start when estimating the cost of a new flat roof, but there are several other factors to consider.

#1. Drainage System

Water drains properly on flat roofs thanks to drainage systems. This system might need to be replaced at the same time as the roof. The cost of replacing a drainage system can vary depending on the type of system and the extent of repair needed. Prices typically range from $600 to $1000. Before you begin, you should inspect the area for any damage or obstructions. It is advised to hire a professional for the job.

#2. Labor Costs

Flat roof installation labor costs for homeowners can range from $3 to $7 per square foot. Additional roofing layers can cost between $1 and $2 per square foot. Some roofers charge by the hour rather than the square foot, with rates ranging from $40 to $80 per hour.

#3. Types of Materials

Your roof’s material selection will significantly affect the overall 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. If necessary, less expensive options such as tar paper or aluminum sheets can be used.

#4. Inspections and Permits

The municipality in which you live will determine whether you need a permit or an inspection to replace your flat roof. In some areas, permits are required for electrical work, plumbing work, and any structural changes to your home, including roofing.

The cost and timeline of your roof replacement project can be significantly impacted by permits. The cost of permits varies greatly depending on the location, size, and complexity of the project. It depends on whether you hire a contractor or do it yourself.

#5. 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 usually included in the labor costs at $3–$7 per square foot.

#6. Sealant for Roofs

Installers should seal the new roof to protect it from weather damage once the old roofing material has been removed and replaced. Sealants also improve shingle permeability, preventing moisture from penetrating.
Depending on whether you have chimneys, skylights, or other areas for the roofers to seal, a typical sealant could cost between $50 and $1,000. Because the laborers do not have to deal with a steep slope, flat roofs are less expensive.

#7. Vent Installation

Roof vents allow air and rainwater to escape from the roof, so if they are missing, they must be installed. Venting also lowers the amount of water that eventually soaks into the roof. Ventilation typically costs $300–$600.

Options for Flat Roof Replacement

Flat roofs may appear unusual, but they are common on homes in the Southwest United States—or any arid region. The drier weather in these regions means architects don’t need to worry as much about water stagnating and causing roof damage.

However, flat roofs are known to leak more often because water doesn’t roll off the way it does on pitched roofs— instead, it just pools until it evaporates. When this happens, the water has more time to find weaknesses in the roof’s surface. If you’ve never had a leaky roof, here are some warning signs:

  • Water damage and stains on your ceiling and walls
  • Bubbling paint
  • Dripping water that isn’t coming from the sink
  • Mildew on the ceiling or exterior walls

If you have an older home or notice leaks, it may be time for a flat roof replacement—here are your options and what they’ll cost.

#1. Metal Flat Roofing

Metal is one of the most frequently used materials for flat roof replacement. The durability of metal, particularly aluminum, is well known. Flat metal roofs can last for almost 35 years in ideal conditions. It also has the added benefit of reflecting heat from the sun, which reduces energy costs. Metal roofing is typically sold in large sheets, but smaller sizes can be ordered to fit around unique features or irregular extensions of your roof, such as small patios or covered stairwells.

#2. Replacing your Flat Roof with EPDM

EPDM (Ethylene Propylene Diene Monomer) is a type of synthetic rubber made from recycled materials. EPDM roofs are both long-lasting and affordable. Don’t be surprised if you hear roofing contractors talk about TPO (thermoplastic polyolefin) interchangeably in conversation at first. EPDM is a very popular option because it’s durable and easy to install, and it has a longer lifespan than metal roofs.

EPDM installations necessitate seaming, which increases the likelihood that water will seep through seams, pull away from the roof, and cause damage to your home. However, the risk of seams pulling away from the roof is greatly reduced if EPDM roofs are spray-applied.

#3. Built-Up Flat Roof Replacement

Tar and gravel combine to form a built-up flat roof (BUR). When many people think of flat roofs, they immediately think of built-up roofs. Built-up roofs have long been popular because, in addition to being visually appealing, they are also effective insulators.

Due to their numerous layers, built-up flat roofs are very durable. The roof is very heavy due to those layers, though. It is a good idea to replace the built-up roof on your home with another built-up roof. If you have a different type of flat roof, consult a licensed roof contractor because you may require additional roof support.

#4. Modified Bitumen Flat Roofing

Modified bitumen is rolled onto your roof, and it is typically secured to your flat roof with a blowtorch. There are, understandably, risks associated with the installation, particularly when an inexperienced roof installer is involved. There are new and safer ways to install modified bitumen, so talk to your contractor about alternative installation methods.

Despite the potential hazards during installation, modified bitumen is simple and quick to install, and it also effectively reflects heat. It’s also an affordable choice, costing between $3 and $6 per square foot. Talk to your contractor about a safer roof if your concerns about installation risks outweigh the benefits.

#5. Spray-Applied Coatings

Spray-applied coatings aid in sealing and preventing water damage to flat roofs. Because the coating is sprayed on, there are no seams to worry about, and it will cover the seams in EPDM roofs for added longevity. While spray-applied coatings are time-consuming to apply correctly, they are well worth the effort and investment because they extend the life of your flat roof.

How to Flat Roof Replacement

So you have a general understanding of the various flat roof materials and their costs, but what can you expect from the installation process? How long does it take to install a flat roof replacement? Working with a skilled commercial roofing contractor, on the other hand, will make all the difference in terms of a quick and efficient installation process.

Step 1

Call a roofing company as soon as you notice the first signs of an aging flat roof. You will schedule a free inspection and estimate, during which we will use innovative technology to document your roof’s condition and any damage. They will then provide a detailed explanation of what was discovered as well as recommendations for repairs or replacement.

Step 2

After you have reviewed their findings, estimate, and recommendations and have decided to hire them for the project, they will send you an agreement outlining the full scope of the work that will be done. They will work with you to schedule a convenient time to begin the installation process.

Step 3

On installation day, the job site supervisor will be your point of contact. A skilled, professionally trained team of flat roof installers will arrive on time to repair or replace your roof. For smaller commercial buildings, installation can be completed in as little as 5 days. In terms of larger buildings, flat roof installation can take up to 2 to 3 weeks.

Step 4

It is their goal to ensure that every customer is completely satisfied with their new commercial roof, so they always strive to complete projects correctly the first time. If you are dissatisfied with the outcome for any reason, likely, they are as well.

How much does a flat-top roof cost?

A flat roof should cost between $250 and $900 per roofing square (100 square feet), or $2.50 and $9 per square foot, including the cost of both roof materials as well as installation and labor.

Is it OK to put a new flat roof over an old one?

Yes. Many commercial and residential flat roof owners are aware that a new roof can be installed on top of an old one. Many old built-up roofs still exist, and many of them have rocks on them.

What is the best material to cover a flat roof?

The top 4 flat roof materials (& how much they cost)

  • EPDM membrane roofing
  • TPO membrane roofing.
  • PVC membrane roofing.
  • Standing seam metal roof.

How often do flat roofs need to be replaced?

between 20-25 years

First and foremost, most flat roofs will last between 20 and 25 years if properly installed with high-quality materials.

What is the cheapest flat roof?

EPDM (ethylene propylene diene monomer) rubber is one of the most affordable roofing materials. It’s so long-lasting that it can last up to 50 years, which is probably why so many homeowners prefer it.

Are flat roofs expensive?

Flat Roofs Are Less Expensive: Flat roofs typically cost between $3,100 and $10,000 to install or $4 to $13 per square foot.


Homeowners with flat roofs 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 cost, we recommend getting estimates from at least three local roofing contractors before making a decision.


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