Photos courtesy EPDM Roofing Association/Jim D. Koontz & Associates

Recent testing suggests ethylene propylene diene monomer (EPDM) roofing membranes provide a high degree of hail resistance over various substrates.

Roof assemblies with non-reinforced ethylene propylene diene monomer (EPDM) membranes offer a high degree of hail resistance over a variety of substrates, according to recent testing.

The research, conducted by Jim D. Koontz & Associates, on behalf of the EPDM Roofing Association (ERA), also suggests the roofs are able to provide protection over time, despite aging.

Tests were conducted on more than 80 samples of 1.5-mm (60-mil) membrane, including new, heat-aged, and field-aged materials. (The last category comprised EPDM removed from existing structures in the field with five to 15 years of actual weather exposure.) In the tests, 24 of the 25 'new' targets were not damaged by 76-mm (3-in.) hail balls, which were propelled by a gun (with National Bureau of Standards technical data applied to determine approximate impact energy).

None of the 20 heat-aged targets failed when impacted with the same size of hail. Fourteen of the 18 field-aged EPDM target samples adhered over a 51-mm (2-in.) thick polyisocyanurate (polyiso) insulation substrate did not fail, and none of the 18 adhered over a 13-mm (0.5-in.) thick oriented strandboard (OSB) substrate failed.

The EPDM material was fully adhered to various 1.2 x 1.2-m (4 x 4-ft) substrates–mechanically fastened polyiso insulation, mechanically fastened wood fibreboard, and 13-mm plywood.

Further information on the study can be found at www.epdmroofs.org.