EPDM roof system EPDM (Ethylene Propylene Diene Monomer) – EPDM is similar to butyl rubber in composition, but has better weather resistance. EPDM is thermoset membrane. It also has good resistance to corrosive chemicals, diluted mineral acids, and vegetable oils. EPDM is not resistant to petroleum products. EPDM is available in plain and reinforced styles.