2022 Cost of Flat Roof Replacement (A Comprehensive Guide)

Kenneth Wilson

More homeowners are considering a flat roof, as it brings excellent energy efficiency, improved aesthetics, and better outdoor living space. Compared to their sloped counterparts, flat roofs also have a relatively more straightforward installation.

So if you’re currently researching flat roof replacement costs, you’re looking at $4,700 to $15,400 for materials and labor. That said, let’s discuss all the cost factors that may fluctuate the total price– including your preferred roofing materials, roof size, and more.

Average Costs of Flat Roof Replacement


Generally, each “square” of a flat top roof starts from $500 to $1,900, covering one hundred square feet. This translates to $5.25 and $18 per square foot, including labor and materials. Keep in mind that the figures above merely serve as a ballpark estimate. If you want to know the actual costs for your home, you may consult a local professional roofer to give you a more accurate estimate.

Costs will vary depending on the quality of the materials used, local labor rates, complexity of the project, and more. (Related: Roof Replacement Cost & Consumer Guide)

Flat Roof Replacement Cost Breakdown


Unfortunately, flat roofs can be easily damaged, given how dirt and debris quickly accumulate on the surface. The lack of a sufficient slope may also cause drainage issues in some cases. In short, a flat roof has a relatively shorter lifespan than a traditional sloped roof. You may be looking at under a decade of use.

Once your flat roof gets damaged beyond repair, you will need to hire a professional roofing contractor for a replacement. Your total budget will be split between materials and labor costs, which may include other factors such as the removal and disposal of the old roof, underlayment, and ventilation and roof drain costs. (Related: Roof Replacement Costs in Florida: Here’s What to Expect)

Let's discuss all the critical cost factors to consider as you set aside the proper budget for your flat roof replacement project:

Labor Costs


Most roofers charge an hourly rate of $40 to $80. A flat roof takes about five days of work, depending on your home's roof size and the project's complexity. You may be looking at labor costs between $2,400 and $4,800.

If you choose more intricate roofing materials like built-up tar, expect the overall labor costs to increase accordingly as it is more time-consuming to install.

Old Roof Removal


To replace a damaged or worn-out roof, you will most likely remove and properly dispose of the old roofing materials to make way for the new. This may be included in the overall quote of your contractor. But, some contractors may also charge an extra fee between $1,500 and $2,250. (Related: How Much Does It Cost To Tear Off And Replace A Roof?)

It would be best to talk to your contractor to determine any additional costs brought by disposal to prepare your budget accordingly.

Average Cost to Replace a Flat Roof by Type


Fortunately, you can choose different roofing materials for your flat roof replacement project depending on your needs, budget, and preference. Each roofing material comes with its unique pros and cons. Before you make a purchase, you may want to talk to a contractor to help you determine the right one for your home needs.

Important Note: As of 2021, roofing material prices in the USA surged 5% to 10% due to increased demand. There may also be delays in sourcing your preferred materials, so we recommend planning ahead of time.

Fiberglass


resistance, and longevity of up to 25 to 50 years, given proper maintenance. However, since it is made of glass– it's not as durable as other materials in the market. You may want to do annual inspections to ensure your fiberglass flat roof is in its prime condition. Costs start from $5 to $7 per square foot.

Rubber


The rubber material is resistant to damage caused by warm weather and frequent harsh UV ray exposure, making it another suitable material for your flat roof project. If your property is located in extreme climate regions, this may just be the right option for your needs. This lightweight material may also last you up to 50 years, given proper upkeep. Labor and materials cost range between $5 to $16 per square foot.

Ethylene Propylene Diene Monomer (EPDM)


Ethylene propylene diene monomer (EPDM) is a unique roofing material derived from oil and natural gas byproducts. This allows homeowners to save on the upfront costs, but the material may start to deteriorate only after 10 to 15 years of use. You may choose from different thicknesses and a black or white color option.

If you want to save on your energy bills, choose black EPDM as it absorbs heat. On the other hand, white EPDM has a cooling laminate layer. EPDM material starts from $6 to $15 per square foot.

Built-up Tar


Since built-up tar layers gradually, the installation process can be rather lengthy. But if you don’t mind waiting, it provides some unique advantages over the other roofing types. For one, tar is fire-resistance and has relatively easy maintenance. The material is also long-lasting, up to 30 years. Expect to pay $5 to $11 per square foot.

Glass-reinforced Polyester (GRP)


Glass-reinforced polyester (also known as GRP) is one of the newest roofing types that solves some of the famous disadvantages of fiberglass. The material is made from plastic and fiberglass, which increases its durability. Note that this material can be rather challenging to install. GRP flat roofs start from $5 to $8 per square foot.

Modified Bitumen


Lastly, we modified bitumen, a single-ply roofing material placed in sheets. The material offers an easy installation, and it is 100% recyclable, making it a crowd-favorite choice among many homeowners. However, it is not genuinely water-resistant and may need timely replacement after 10 to 20 years. Costs start from $5 to $8 per square foot.

Other Cost Factors to Take into Consideration


Every home has unique needs, making your flat roof replacement project a somewhat complex process. Here are some other vital factors to consider as you price out the total cost of replacing your flat roof.

  • Sealing the Surface: To make routine maintenance easier on your end, opt to apply a sealant or coating to your new flat roof. This serves as an extra waterproofing layer and increases its fire resistance and general durability. Expect to spend an additional $800 to $2,700.
  • Ventilation and Roof Drains: A sound drainage system is crucial for flat roofs. If your contractor believes you need to install new drains or gutters or re-route some existing drains, this will cost you an extra $1,000 to $1,800. Since some flat roof materials may absorb heat more than you’d want them to, it’s also essential to ensure proper ventilation. A single roof vent installation starts from $500 to $1,200.
  • Permits and Inspections: Depending on the location of your property, you may be required to secure a building permit for a flat roof replacement. This may cost you $450 to $750 (or more). Permit costs will increase for large roofs measuring more than 1,000 square feet.

Frequently Asked Questions (FAQs)


Why do flat roofs leak?

Flat roofs allow the water to stand on top of it, and the longer the water is there, the more likely it is to find its way inside your property. You must consider improving the drainage system to remove the water from your roof faster.

Can I repair my flat roof instead of replacing the whole thing?

If your roof's damage is not extensive enough for you to be granted a complete replacement, then yes, you can repair it instead. It will cost you around $450 to $900 to patch small tears and perform simple repair jobs. Meanwhile, more extensive repairs may cost $1,500 or more.

When should I replace a flat roof vs. opt for a repair?

It may be best to replace your flat roof if it is older than 15 years old and if the repair cost is expensive. Flat roofs are made with TPO membranes nowadays, and their life expectancy is 15 to 25 years. On average, a flat roof replacement in the DMV area is $22,500 per 15 square roofs. It is unwise to repair an aging roof because it can be costly in the long run.

Kenneth Wilson
March 14, 2022
Cost Guides, Roofing

Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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