Until the 1960s, built-up asphalt and coal tar pitch roofing systems were the primary options for low-slope commercial roofing installations. Then other materials began to appear on the market – single-ply membranes, including modified bitumen (an evolution of built-up), and thermoset and thermoplastic systems.
Thermoset membranes (primarily EPDM today) are vulcanized materials made from cross-linked molecules that provide elasticity. Once the material is produced and “set” it’s hard to bond and can’t be softened by heat. Thermoset roofing materials can’t be heat welded, and require adhesives for installation seaming.
Thermoplastic membranes (PVC, TPO and some others), first used in Europe in the 1960s, do not contain cross-linked molecules, so they do not “set.” These materials “flow” when heated, enabling membrane sections to be effectively and securely heat-welded together during installation.
TPO (thermoplastic polyolefin) systems have been on the market about 15-20 years, but most installations have been done in past 10 years. TPO combines the flexibility and weather resistance of EPDM and heat-weldability/chemical resistance of PVC. It’s the most-installed commercial roofing system in North America and the fastest-growing single-ply segment.
PVC (polyvinyl chloride) roofing has a 30-plus-year track record in the US. It provides excellent fire, oil, and chemical resistance, as well as excellent weathering and seaming. PVC membranes can be factory prefabricated and, because they don’t “cure” on the rooftop, remain weldable for years after their installation. PVC roofing has maintained a steady share of the commercial market in recent years.
Here are a few more characteristics of TPO and PVC roofing:
Regardless of the type of roofing system you choose, its long-term effectiveness ultimately comes down to the experience of the contractor doing the installation. Royalty has been installing roofing systems since 1986. If you’re considering a roof installation or replacement, we would welcome the opportunity to discuss your needs and our capabilities. Please contact us at your convenience.