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.
These materials provide a flexible solution to structural movement and thermal shock. They are less affected by crude oil price and availability. Typically manufactured using lighter-colored materials, single-ply membranes reflect heat and save energy. They are installation-friendly, with a variety of attachment methods.
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.
Thermoplastic roofing is the fastest growing segment in the commercial roofing industry, with a proven history of performance on buildings of all types and in all climates. Ease of installation means excellent rooftop seaming and lower liability for contractors. Some thermoplastic manufacturers have full code compliance and certification nationwide, including the International Building Code, Underwriters Labs, and Factory Mutual, to name a few. Thermoplastics are lightweight and, because of high reflectivity, energy efficient.
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:
- Resistant to bacteria, dirt, debris build-up
- Good vapor, chemical, UV resistance
- White membrane delivers high reflectivity and energy savings
- Installation can be mechanically attached, adhered, or ballasted
- Rooftop welding is sensitive to job site weather conditions
- Contact with oil, grease, wax can cause problems
- Fire retardants can attack UV stabilizers
- Susceptible to high-heat degradation
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.