Independent study shows EPDM roofing membrane offers resistance against hail, regardless of the age of the tested membrane

August 11, 2010

BETHESDA, MD., February 19, 2009 – In recent testing conducted on behalf of the EPDM Roofing Association (ERA), non-reinforced EPDM roof assemblies were found to offer a high degree of hail resistance over a variety of substrates and this level of performance is maintained even as the membrane ages.  The test results provide scientific validation of existing empirical data, showing that EPDM roof systems faired very well in hailstorm events, and maintained that performance over time.

The tests were conducted for ERA by Jim D. Koontz & Associates, of Hobbs, N.M., on more than 80 samples of 60 mil membrane, provided by manufacturers Carlisle SynTec and Firestone Building Products.  Tested material included new, heat aged and field aged EPDM.  Field aged EPDM was comprised of EPDM roofing material that was removed from existing structures in the field with 5 to 15 years of actual weather exposure.  

In the tests, 24 of the 25 “new” test targets were not damaged by 3.0” hail balls.  None of the 20 “Heat Aged” targets failed when impacted with 3.0” hail balls.  14 of the 18 “Field Aged” EPDM target samples adhered over a 2” thick polyisocyanurate insulation substrate did not fail,  and none of the 18 adhered over a ½” thick OSB substrate failed.  

“Given the millions of dollars of economic loss caused each year by hail damage, and with the nation going through a period of increased hail activity, property owners and building professionals see increased value in installing hail resistant roofing systems,” said John Geary, Vice President of Technology at Firestone Building Products, and chairman of the EPDM Roofing Association’s (ERA) board of directors.  “These test results provide firm evidence of EPDM’s high level of performance.”

The EPDM material was fully adhered to various 4’-0” x 4’-0” substrates:  mechanically fastened polyisocyanurate insulation, mechanically fastened wood fiber board and ½” plywood.  Hailstones ranging in size from 1.5 to 3.0 inches were propelled at the membranes by a hail gun, applying National Bureau of Standards technical data to determine approximate “impact energy.”

“In the course of this testing, we attempted to determine in a lab setting how an EPDM roof would withstand some degree of hail impact over a significant portion of its expected service life,” said Scott Long, EPDM Product Manager for Carlisle SynTec Incorporated and a member of ERA’s Technical Committee.  “We believe that this test confirms EPDM’s strong performance in hail testing.”

Jim D. Koontz & Associates, Inc. provides laboratory testing of all types of roofing materials. Testing is performed in accordance with ASTM and other federal and industry standards.

“In addition to conducting this test, we have extensive experience examining numerous rooftops using the EPDM membrane that were impacted by severe hail, up to softball size,” Koontz said.  “In those cases, the non-reinforced EPDM over polyisocyanurate did not fail, and the test results we conducted validated that performance.” 

Further information on this study can be found on ERA’s Web site, at

With more than 45 years of success as a roof system of choice for low-slope applications, EPDM is the leading roofing choice of architects, roof consultants and contractors for both new construction and replacement roofing projects, with more than 20 billion square feet of EPDM installed on more than 500,000 warranted roofs. 

The EPDM Roofing Association (ERA) is the first trade association solely representing the manufacturers of EPDM single-ply roofing products and their leading suppliers.  ERA provides technical and research support to the public and the construction industry, and communicates the longstanding attributes, consistency and the value proposition of EPDM rubber membrane roofing materials.

George Evanko
George Evanko Communications
(703) 848-1655


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