With so many options for flat commercial rooftops, it can be difficult to choose which roofing membrane to go with. One of the three common type of roofing membrane is EPDM, which stands for Ethylene Propylene Diene Monomer. EPDM is a flexible synthetic rubber that has been used for roofing for over forty years and continues to enjoy a large share of the commercial roofing market. EPDM has also been used for pond liners, terraces, tunnels, and garden roofs. EPDM roofing is a thermoset material, where counterparts PVC and TPO are thermoplastic and a blend of the two, respectively. EPDM membranes are available in three typical thicknesses: 45, 60 and 90-mil. A 60-mil EPDM roof membrane typically weighs around .43 pounds per square foot, slightly more than a 60-mil PVC membrane (.36).
EPDM membrane is often used in ballasted roofing systems. Because exposed EPDM roof systems tend to shrink over time and pull away from edges and other terminations, the ballast helps keep the roof in place and minimize shrinkage. And for black EPDM roofs (the most common), ballast also offers reflectivity that’s comparable to lighter colored membranes.
One of the biggest advantages of EPDM is the price. EPDM is generally cheaper than other commonly installed (PVC and TPO). Another is that EPDM membranes can be installed in wide rolls. This enables a quicker installation and lessens the number of seams, which in turn helps lessen the possibility of leaks.
While EPDM has some advantages, it does have some drawbacks.
Although EPDM may be cheaper than TPO and PVC, it has long-term durability issues. Rooftop seams are glued together on the rooftop, and that adhesive tends to deteriorate over time, creating gaps between membrane sections. EPDM also has poor resistance to grease and other petroleum-based materials, which may not be ideal for some commercial buildings, like restaurants.
Exposed black EPDM membranes can increase building energy costs and contribute to the urban heat island effect. As mentioned above, covering the EPDM roof membrane with ballast helps mitigate those reflectivity issues, but ballast adds to the cost of the installation.
All commercial roofing systems have their pros and cons. As with any roof installation, the quality of the job usually comes down to the quality of the contractor doing the work. Make sure you choose one who has expertise in the system or systems you’re considering.