Your Complete Commercial Roofing Systems Guide

What goes into choosing a commercial roofing system? Of course, cost plays a part, but you also have to consider the weather conditions the roof is likely to encounter, the building’s style, what the building is used for and whether the roof is flat or slanted. Most commercial roofs are either flat or nearly flat, but there are exceptions. This guide will help give you some direction as you work with your roofing systems specialist to make your decision.

Commercial Roofing Technology and Materials

Commercial roofing systems have been around for a long time. However, to meet new requirements for environmental responsibility, energy savings and other factors, new materials and technologies have entered the market. These technologies and materials provide an expanded array of choices to suit your specific needs.

Older technologies and materials, such as those used in built-up systems, remain strong alternatives for many applications. However, newer systems, including EPDM, PVC and TPO, use thermoplastics or rubber to reduce weight and resist high temperatures, fire and UV radiation. You’ll find more about the available systems below.

How to Choose the Right Commercial Roofing System

The first consideration in selecting a roofing system is whether your roof is low or steep slope. Low-slope roofs, also called flat roofs, are most common on commercial buildings. They often have just enough slope to allow water to run off. Steep slope roofs are less common on commercial buildings, and they are visible from the ground, so the way they look is more important.

When you know the slope you’re dealing with, you can select the system. This step is best taken with the help of a commercial roofing professional who can help you determine which materials are best suited to your application.

Commercial Roofing Systems: An Overview

Most commercial buildings use at least one of 13 roofing systems:


A durable synthetic membrane, EPDM (Ethylene Propylene Diene Monomer) has been popular for its cost-effective performance for more than 30 years. It remains flexible despite temperature extremes, withstands harsh conditions and lasts up to 25 years. Other EPDM benefits include:

  • Light weight, putting less stress on the structure
  • Strong performance record over 40 years
  • Low maintenance
  • Heat- and fire-resistant
  • Not affected by UV radiation
  • Flexibility accommodates structural movement

The simplicity of applying an EPDM commercial roofing system, in addition to its durability, accounts for its popularity. For example, the seams can be sealed in two ways, the first requiring two steps, the second only one:

  • Method 1: splice adhesive–adhesive applied to the seam followed by a lap sealant applied to the edge of the seam.
  • Method 2: peel and stick–adhesive tape applied to the seam forming a stronger, longer-lasting bond.

You can get an EPDM roofing system in either black or white. Black has proven more popular because of its lower cost.

PVC Membrane

In use for more than 50 years, PVC (Polyvinyl Chloride) roof systems can last as long as 30 years. A heat-welded process makes the bond between sheets permanent, so the chance of leaks is greatly reduced. These systems have also earned the Energy Star rating because they can cut your overall energy costs by as much as 50 percent.

Other benefits of PVC membrane commercial roofing systems include:

  • High resistance to water ponding, fire, fungi and UV radiation
  • Environmentally friendly


TPO (Thermoplastic Polyolefin) roofing systems manufactured in the United States have gained in popularity because of their relatively low cost. However, compared to PVC, they have some drawbacks:

  • After 20 years of modification, TPO has performance issues, particularly when used in locations with hot climates and high UV radiation. PVC shows high resistance to UV radiation and heat.
  • TPO watertightness is hard to determine because seam-welding bleedout and prolonged delay in the time required before probing the seam creates quality-control problems. With PVC, permanent heat-welded seams prevent leaks. Bleedout during seam welding is obvious, and seam probing can occur immediately.
  • Even when the flame has been removed, TPO continues to burn. POV will not continue burning when the flame has been removed.
  • Cut membrane edges on TPO must be sealed to prevent water absorption, even if the cuts are performed at the factory. PVC edges require no sealant.
  • Patching or re-welding TPO can be difficult. PVC presents no such challenges.
  • Cold weather, or thick membranes make TPO hard to work with because it becomes stiff. PVC’s flexibility makes it easy to work with under adverse conditions.

In short, TPO remains in its experimental stages. Although it’s not as expensive as PVC initially, it’s less likely to match PVC in performance or service life. So, in the long run, TPO could even cost more than PVC.

Modified Bitumen

Modified bitumen, also known as APP (Atactic Polypropylene), has been a popular alternative in commercial roofing for more than 30 years. It combines asphalt, polymers and fillers and is easy to repair and maintain. Other benefits of modified bitumen roofing material include:

  • Long service life
  • High durability
  • Simple inspection

A single-ply system, modified bitumen comes in 3′ x 33′ rolls. When applied, the rolls overlap each other. Most often, crews use torches to heat the rolls and seal the seams..

Because of rising insurance costs, modified bitumen has grown less cost-effective. However, repairing this roofing system remains highly cost-effective as it can add years to its life.


Spelled out, the name says it all. BUR (built-up roofing) is just that. It consists of layers of bitumen or asphalt and fabric with gravel or aggregate stone making up the final layer.

You’ll find three kinds of built-up roofing systems on the market:

Ballasted Asphalt

A ballasted asphalt built-up roof system uses larger stones as its top layer because it isn’t attached to the roof membrane. This tactic, plus strategically placed fasteners and plates prevent any movement. The system can be installed no matter what the weather, and the finished roof is highly fire-resistant.

Cold Built-up

Like the ballasted asphalt system, a cold built-up roof can be installed in any weather, using a squeegee. No toxic fumes are emitted during installation.

Hot Built-up

The most difficult built-up roofing system to install, hot built-up, requires liquefied bitumen and, during installation, releases hazardous fumes and vapors.

Advantages and Disadvantages of a Built-up System

A BUR can last up to 30 years. Other advantages include:

  • Strong resistance to UV radiation
  • Longer life under changing weather conditions
  • Waterproof

Built-up roofs take longer to install than other systems. Additional disadvantages include:

  • High installation cost
  • Potential for damage from water and wind


With the elasticity to expand and retract without harm, a roof coating serves as the top layer of a roofing system. It protects the rest of the system from infrared and UV radiation and weather-related damage.

The advantages of coating include:

  • Low cost
  • Environmental friendliness
  • Durability
  • LEED (Leadership in Energy Efficiency and Design) certification
  • Lowered roof-surface temperatures
  • Reduced energy costs
  • No disposal in landills

Liquid Applied

This system provides a waterproof barrier consisting of resin and polyester reinforcement either sprayed or rolled on. It can be used on all types of existing roofs.

Like a coating, a liquid applied system has no seams, so it provides excellent waterproofing. During application, noise and disruption are minimal. This highly reflective material lowers energy costs by reducing the surface temperature of the roof by 50˚ to 80˚F.

Steep Slope

For roofs with a slope of 3:12 or more, several systems will serve as covering:

  • Asphalt shingles
  • Asphalt composition rolls
  • Wood shakes and shingles
  • Fiberglass laminate shingles
  • Fiberglass 3-tab shingles
  • Slate
  • Clay tiles

The advantages of these materials include:

  • Good resistance to extreme temperatures and wind
  • Often recyclable
  • Availability of LEED or other green building credits


For steep-slope commercial applications, a metal roofing system is a long-term solution. It costs more upfront but can last a lifetime. Standing seam metal roof systems seem to be the preferred choice for commercial buildings, not only because of their durability but also because of their appearance.

Installed over steel beams, the standing seam panels are easily installed by professionals with the right equipment. Once installed, the roof needs virtually no maintenance. When the roof outlives its usefulness, it can be recycled.


Also known as a living roof, a green system covers part or all of the roof with plants. Extensive green roofs require as little as three inches of soil and need little maintenance. Intensive green roofs provide the ability to expand the variety of plants but usually require more than eight inches of soil.

Green roof systems offer a number of benefits:

  • Reduced water runoff and improved water quality
  • Reduced urban heat island effect
  • Wildlife habitat restoration
  • Less air pollution
  • Noise reduction


Its ability to make your roof a source of energy makes the solar alternative highly attractive. Installed over an existing roofing system, it consists of solar panels and supporting distribution technology. The cost of solar panels continues to go down, and tax incentives, along with the savings in energy costs and the environmental benefits of clean energy could add to a solar system’s attractiveness.

Talk to the Experts at Summit Commercial Roofing

Choosing a commercial roofing system is too important to leave to chance or guesswork. You need the advice of a professional to select the best system for your needs. Visit our website or call (724) 272-4025 for a consultation and an estimate.

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Contact Summit Commercial Roofing Today

Summit Commercial Roofing is proud to be an industry leader in commercial flat roofing replacement, repairs, maintenance and installations. Courtesy, integrity, and transparency are a big part of everything that we do. Are you ready to see why we’re one of the best commercial roofing companies in Southeast Michigan? Call (734) 564-0371 or fill out our online form today to request a quote on our commercial roofing services.

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