The Complete Commercial Roofing Guide

complete commercial roofing guide

Our guide to commercial roofing outlines the different commercial roofing systems available as well as costs to install, repair, and replace them; and answers frequently asked questions related to commercial roofs.

On this page, we discuss...

Commercial Roofing Systems

There are 5 primary classifications of low-slope commercial roofing systems:

  1. Single-ply roofing (EPDM, TPO, PVC)
  2. Metal roofing
  3. Modified bitumen roofing
  4. Built-up roofing
  5. Liquid applied roofing

The most widely used commercial roofing system in the United States is the single-ply roofing system, including EPDM, TPO, and PVC roofing systems.

Commercial Roofing System Pros & Cons
Commercial Roof Type Pros Cons
Single-ply roofing
offers lightweight durability,
pliable for various temperatures,
repairs easily,
low-cost option
susceptible to water retention,
thin surface easily punctured,
relatively short lifespan
Metal roofing weather & fire resistant,
long term warranties,
lower energy bills
expensive upfront cost,
can dent in harsh weather
Modified bitumen roofing very durable,
weather & fire resistant
low-cost option
only color option is black,
high heat absorption
Built-up roofing low-maintenance,
offers UV protection,
excellent waterproofing
slower installation,
noxious fumes during install
Liquid applied roofing reduces installation costs short lifespan


Commercial Roofing Cost

Commercial roofing costs can vary quite a bit. Your price will depend on your roof's square footage, the type of roofing system you want installed, and the geographic location of the installation.

Commercial Roofing Cost Breakdown:

Average cost to tear out existing flat roofing...............................$2 - $4 per sq. ft.

Average cost to install modified bitumen or built-up roof............$3 - $7 per sq. ft.
Average cost to install EPDM, PVP, or TPO roof........................$5 - $10 per sq. ft.

Average Cost to Install Commercial Roofing Systems
Size of Roof Modified Bitumen or Built-Up Roofing EPDM, PVP, or TPO Roofing
3,000 sq. ft. $15,000 $22,500
4,000 sq. ft. $20,000 $30,000
5,000 sq. ft. $25,000 $37,500
6,000 sq. ft. $30,000 $45,000

See how much others have paid for their commercial roof.

If you're replacing your roof and need to remove the existing one, help contain all that debris with a large dumpster. Our Dumpsters 101 Guide is a great place to get started.

Find a dumpster rental provider near you.

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Commercial Roofing Maintenance

Commercial roofing maintenance is a critical part of maximizing the lifespan of a commercial roof. Maintaining a commercial roof isn’t difficult or time-consuming; it’s just a matter of keeping the roof clear of tree limbs, fallen debris, excessive snow, and pooling water and inspecting the roof for swelling or blisters.

If any part of the roof looks “abnormal,” contact your local roofing contractor right away to address it before it becomes a far more serious problem.

A regular annual maintenance plan can help extend the life of a roof by up to 50%.

Regular maintenance can help prevent leaks and other roof damage, and it may even help preserve the roof insulation enough to reuse it the next time you install a new roof, saving you as much as 30 - 40% on the new installation.

Oftentimes, roofing warranties become void when proper maintenance is ignored, so be thorough when reading through the warranty details. Ask your contractor to go over the warranty with you carefully so you know exactly what you're getting.

Commercial Roofing Building Codes

There are building codes in place for commercial roofing applications you must comply with. These standards are enforced by local and state government agencies to help maintain safety standards and public welfare in commercial buildings.

Your local roofing contractor is the best source for determining your city’s commercial roofing standards and building codes.

Although building codes vary from state-to-state, many locales have adopted the standards set by all or some of the following organizations:

  • International Code Council (ICC)
  • National Fire Protection Association (NFPA)
  • American Society for Testing and Materials (ASTM)
  • FM Global
  • Underwriters Laboratories (UL)
  • American National Standards Institutes (ANSI)

White commercial roofing

Commercial Roofing FAQ

How is the square footage of a commercial roof measured?

Most roofs are measured in squares—1 square is equal to 100 square feet.

When trying to calculate how many squares of roofing material you'll need for your commercial roof, it can help to create a sketch of the roof and divide it into manageable, rectangular sections in order to make the calculations easier. Then, use the following formulas...

Length of roof x Width of roof = Roof square footage

Roof square footage ÷ 100 = Number of roofing squares you'll need

What’s the most durable type of commercial roofing material?

Commercial metal roofing is among the most durable roofing systems on the market, but metal roofs require at least 4% slope, according to the National Roofing Contractors Association (NRCA).

For flat roofs—or those with less than a 4% slope—a built-up roof membrane provides increased durability over most single-ply roofing systems.

What’s the most common cause of commercial flat roofing leaks?

The vast majority of leaks in commercial roofing applications occur at transition areas, such as chimneys, vents, flashing, and AC units.

A good commercial roofer will take ample time to ensure his/her “flashing detail” is done correctly. A good installation is imperative to preventing a leaky roof in the future.

My industrial roof is old and starting to leak, does it need to be completely replaced?

Commercial-industrial roofing systems are designed to last for decades, so even though it may be old and starting to leak, that doesn’t necessarily mean it requires a complete tear-off and replacement. If it’s rubber roofing, such as EPDM or any other common type of commercial roofing, the fix is often as simple as some patchwork.

Patching up leaks is far less expensive than replacing the entire roof, and it’s an effective strategy for maximizing the life of the roofing system.

Your roofing contractor will discuss these options with you, so you can determine whether a patch-up is an option or a complete replacement is in order.

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What are the top commercial roofing system manufacturers?

Several of the biggest manufacturers of commercial roofing systems include GAF, Duro-Last, Soprema, GenFlex, Carlisle, Versico, Firestone, and many more.

Talk to your commercial roofer about your options, and be sure to choose a contractor with plenty of experience installing the roofing system of your choice.

Does commercial flat roofing require a pitch?

Not necessarily. A pitch—or slope—can be added to a new roof installation to help with drainage, but it isn’t a necessity in most cases.

What does “R-Value” refer to in the commercial roofing industry?

R-value measures how effective a roof is at insulating the building from radiant heat. A higher number is better and can help reduce the cost of cooling a building in the summer.

What are some sustainable roofing options?

Green and sustainable commercial roofing systems abide by the standards developed by the U.S. Green Building Council.

Most types of roofing systems offer green alternatives that include one or more of the following advantages:

  • Longer than average lifespan (usually 50 or more years)
  • High R-value
  • Made from recycled materials
  • Vegetative roofs (sustainable rooftops consisting of plants)

Commercial roofing systems that are considered eco-friendly and sustainable options by the U.S. Green Building Council are given the LEED—Leadership in Energy and Environmental Design—stamp of approval.

What makes a roof LEED-certified?

LEED certification means a roof was independently verified to meet standards of energy efficiency, sustainability, and environmental health.​

In 2000, the U.S. Green Building Council (USGBC) developed LEED–Leadership in Energy and Environment Design—as a rating system for builders across the United States.

What is a "cool roof?"

A cool roof is one that reflects the sun’s heat rather than absorbing it. This helps reduce the cost of cooling a commercial building and is better for the environment.

The Cool Roof Rating Council (CRRC) determines the overall “coolness” of a roof by measuring its solar reflectance and thermal emittance. Both factors are given a score between 0 and 1 to determine the roof’s overall coolness value—a higher number is better.

What are the benefits of white roofing?

Many businesses are turning to white roofing solutions for multiple reasons. Some of the benefits of white roofing on commercial buildings include:

  • Higher reflectivity to help reduce the cost of cooling a building
  • Tax incentives offered by some local and state governments for using “cool roofing”
  • Lowers the “urban heat island” effect, which causes the temperature in urban areas to be several degrees warmer than rural areas

Are there any benefits to having commercial asphalt roofing?

Asphalt roofing is another option for commercial buildings and offers several benefits:

  • Widely available
  • Inexpensive installation and maintenance
  • Provides multi-layer protection against the elements
  • Solid track record—used for more than 100 years

What causes rubber roofing to swell?

Rubber roofing, particularly EPDM, will swell when exposed to aerosols, refrigerants, and other halogenated and aliphatic solvents. Vegetable oils can also cause swelling of rubber roofing membranes with kitchen and restaurant applications.

An alternative to EPDM that is far more resistant to solvents, grease, and oils is epichlorohydrin (ECH). It looks similar to EPDM but doesn’t swell when exposed to the aforementioned substances.

Should I be concerned with blisters forming on my flat roofing?

Yes, when rubber roofing blisters, it’s a sign that moisture is seeping underneath the membrane. It can lead to severe problems down the line, including major leaks and mold.

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