EPDM Roofing Systems

The EPDM (ethylene propylene diene terpolymer) rubber roofing membrane has been an appealing choice of the low-slope commercial roofing industry for over 40 years. EPDM continues to be a top choice of architects, roof consultants and contractors for both new construction and replacement roofing projects.

The greatest test of any construction material is how it performs under actual field conditions. Forty years of empirical experience in field applications has shown EPDM to have the roofing industry’s longest average service life. Characteristics that contribute to this superior overall system performance include:

  • Cyclical membrane fatigue resistance
  • Proven hail resistance
  • High resistance to ozone, weathering and abrasion
  • Flexibility in low temperatures
  • Superior resistance to extreme heat and fire
  • Thermal shock durability
  • Ultraviolet radiation resistance

EPDM’s high resistance to wind damage has also proven to be an increasingly desirable attribute. These roof systems can be designed to meet a variety of wind uplift criteria from Factory Mutual, including 1-60, 1-90, and 1-120 ratings and greater.

What is EPDM?

EPDM is an extremely durable synthetic rubber roofing membrane  (ethylene propylene diene terpolymer) widely used in low-slope buildings in the United States and worldwide. Its two primary ingredients, ethylene and propylene, are derived from oil and natural gas. EPDM is available in both black and white, and is sold a broad variety of widths, ranging from 7.5 feet to fifty feet, and in two thicknesses, 45 and 60 mils. EPDM can be installed either fully adhered, mechanically attached or ballasted, with the seams of the roofing system sealed with liquid adhesives or specially formulated tape.

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Different EPDM Systems

WHITE EPDM

White EPDM combines the high-performance standards of traditional EPDM with a highly reflective, environmentally friendly surface designed to cut energy costs. In addition to the oils and the polymers used to make an EPDM membrane, another ingredient is added to the mix to enhance UV resistance. In the case of a black membrane, carbon black is added, which converts UV rays into heat. With white membrane, in lieu of carbon black, titanium dioxide is typically used to reflect UV rays and prevent it from attacking the polymer. When used appropriately, usually in warm climates, white EPDM can reduce air-conditioning costs without sacrificing durability of the roofing system. Because of its reflectivity, white EPDM is installed using mechanically attached or fully adhered systems.

THE BALLASTED SYSTEM

Ballasted systems, the workhorse of the three EPDM roofing systems, account for approximately 35 percent of EPDM installations today. Using large panels measuring up to 50 feet by 200 feet, the ballasted system provides fast coverage at a relatively low cost. The EPDM panels are loose-laid over the insulation and held in place by smooth, river-washed stoned or concrete pavers. Ballasted systems are primarily used for large new construction projects, but can also be used on roof replacement or recovery projects where the existing structure can support the additional weight. Ballasted systems are traditionally the easiest of all systems to install and have earned the Underwriters Laboratories Class A rating.

THE MECHANICALLY ATTACHED SYSTEM

Mechanically attached systems can be installed using large panels and attached through the membrane, or using narrow panels attached in the side laps. Non-reinforced or scrim reinforced membranes can be used, depending on the needs of the building owner. The membrane is then attached using either round plates of batten strips to the underlying deck. Mechanically attached systems are lightweight and are ideal for all building sizes and configurations.

THE FULLY ADHERED SYSTEM

Fully adhered systems using panels measuring up to 30 feet by 100 feet. The membrane is bonded to the insulation, which has been physically attached, utilizing mechanical fasteners, stress plates and/or adhesives. Either non-reinforced or scrim reinforced membrane can be used, with the non-reinforced membrane making up most adhered installations. Fully adhered systems are lightweight and ideal for a wide range of building sizes and geometric configurations, including high-slope applications. Because of recent technological advances in application, the fully adhered system is becoming the system of choice for roof replacement applications in many areas of the country.

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Ease of Installation

EPDM’s application methods (ballasted, fully adhered and mechanically attached) allow the membrane to be installed on slopes with positive drainage up to and including vertical applications for fully adhered systems. Good roofing practice always includes provisions for proper drainage for any type of roof system and in most cases, is dictated by local building codes. Because EPDM remains stable over a wide range of temperatures, it allows for year-round installation in all climates.

Repair & Restoration

One of the unique attributes of EPDM is its ability to be easily repaired and restored – an attribute never seen before in the roofing industry.

Even after years of in-field service and exposure to the elements, repairs or modifications involving the installation of a new roof curb into an aged roof can be accomplished easily, with the expectation of long-term performance.

Unlike other roof systems that may degrade and become brittle over time from ultraviolet exposure, EPDM maintains its integrity and flexibility. Because of this, EPDM allows for modifications as easy as washing the membrane, preparing the surface and applying the repair material, including coatings.

Another unique attribute of EPDM is its ability to be restored. Aged and damaged EPDM roof systems are now being restored to original installation quality without major costs or disruption to business. In some situations, when system enhancements are incorporated, the aged roof system is restored to a condition that exceeds that of the original installation.