Roofing System

EPDM (ethylene propylene diene terpolymer) rubber roofing membrane is a highly effective and durable membrane for low-slope commercial roofs that has been utilized for more than 40 years. The primary ingredients of ethylene and propylene, are derived from oil and natural gas. The membrane comes in a variety of widths ranging from 7.5 feet to 50 feet and a thickness of 45 and 60 mils.


EPDM can be installed either fully adhered, mechanically attached or ballasted with the seams sealed with liquid adhesives or specially formulated tape. The building’s roof structure and slope will determine which approach is appropriate. From concrete, wood, or metal, the interior esthetics and overall budget are all considerations in determining the approach used to secure the EPDM system.

Prior to installation, a layer of insulation will be attached to the roof deck to provide a vapor barrier between the deck and the membrane itself. The insulation options include:

Polyisocyanurate (Polyiso) – Polyiso is the most commonly used insulation which ranges in thicknesses to provide the ideal R-value for your application.

Expanded Polystyrene (EPS)  – EPS provides the highest R-value per dollar and will not retain water overtime.

Extruded Polystyrene (XPS) – EXP normally falls between Polyiso and EPS in terms of performance and price. It is semipermeable with a perm rating of 1.

Ballasted EPDM System –

Nearly 35 percent of all EPDM installations are ballasted system which remains one of the most durable roofing systems on the market today. The EPDM is loose laid over the roofing deck and a protective felt membrane then covers the membrane to protect it from a layer of either smooth stone or concrete pavers which hold the membrane in place.

Mechanically Attached EPDM System–

A mechanically attached system is a more popular approach where the EPDM rubber panels are attached using either round plates or batten strips to the roof deck. A mechanically attached membrane roof system is lightweight and ideal for all building sizes and configurations.

Fully Adhered EPDM System–

A fully adhered EPDM rubber roof system is where the membrane is bonded to the insulation, which has been mechanically attached with fasteners, stress plates or adhesives. Fully adhered systems are lightweight and can be used in unique geometric configurations and high-slope applications.

Best Uses For EPDM Roofing Membrane:

Low Slope/Flat roofs with minimal drainage – EPDM can withstand standing water more so than other membranes. The black membrane enhances the ability for evaporation. Additional evaporated standing water can leave silt spots which can amplify the sun’s rays causing the membrane to get extremely hot. Because of EPDM rubbers composition, it will not be damaged by extreme heat.

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In Summary

The following characteristics of an EPDM membrane include:

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


All our EPDM roof installations come with a 20-year manufacturer’s warranty that stands behind the integrity of the product. WNC Roofing utilizes both Firestone and Carlisle 60 mil EPDM membranes and adheres to the manufacturer’s installation requirements to maintain the 20-year warranty for all roofs we install.

A post-installation inspection is conducted by the manufacturer following each of WNC Roofing’s projects before a final sign-off for the 20-year warranty is approved. Additionally, WNC Roofing provides a two-year workmanship warranty to cover all installation aspects.