Best Practices from the Heart of Hail Alley
Texas roofers know a thing or two about hail. Part of “Hail Alley,” the state had an average of 709 major hail events per year from 2017 to 2019, with hail at least 1 inch in diameter.1 And Texas accounted for a full 23% of all hail-related property loss claims made during that period.2
“All of Central and North Texas gets annihilated by hail at least once a year. Sometimes more than that,” said Mike Anderson, general manager of Clark Roofing in Waco, Texas.
As a result, most of the firm’s commercial projects are designed to meet hail coverage requirements, and many to meet Severe or Very Severe hail coverage requirements.
While most of the country isn’t subjected to the pounding that Texas takes, hail does extensive damage from coast to coast every year, with 16,047 major hail events1 and more than 3 million property loss claims nationwide2 from 2017 to 2019.
Anderson shared tips and best practices for specifying and installing single-ply roofing systems that can withstand hailstorms, regardless of where the building is located.
A Thick, Hail-Resistant Membrane
Clark Roofing’s go-to single-ply membrane is 80-mil Standard TPO.
“It is by far the best roofing system out there in terms of durability and getting hail ratings and FM Global coverage,” Anderson said. “We do a lot of work with municipalities, the State of Texas, and the United States military. They want a long-lasting, durable product and are willing to pay a bit more for it.”
He continued, “TPO can handle the Texas heat. PVC plasticizes in hot climates; the membrane breaks down and deteriorates rapidly as the plastics in it leach out. TPO isn’t as susceptible to that, making it much more durable.”
The thicker 80-mil membrane also withstands Texas’ hailstorms, making roofing systems eligible for 20-year system warranties covering hailstones up to 2 inches in diameter.
The one set of conditions for which Anderson recommends PVC roofing systems is restaurants and other buildings were the roof will regularly be exposed to grease or oils. PVC is highly resistant to chemicals like these, which can cause other single-ply membranes to deteriorate, blister or become soft and spongy.
A Strong, Wrinkle-Free Bond
A wrinkle-free installation is key to maximizing hail resistance, Anderson said.
“The roof needs to be very tight,” he explained. “If there are places where the membrane isn’t touching the substrate, hail has a better chance of puncturing it.”
To prevent wrinkles – and achieve a better-looking roof – Clark Roofing recommends full adhesion.
“We always fully adhere if the building owner has the budget because it looks so nice,” Anderson said. “It’s more expensive and time-consuming than mechanical attachment, but the results are better.”
And when seeking a Severe or Very Severe hail rating, a fully adhered system is the only option. “If a large piece of hail strikes a plate or screw, it can damage the membrane,” Anderson explained. “So, the system is fully adhered, with plates and screws only used on the roof perimeter to meet wind uplift or FM Global requirements.”
Clark Roofing crews use solvent-based adhesives, such as TPO Bonding Adhesive from Mule-Hide Products, to secure the membrane.
“It flashes better and delivers a stronger bond,” Anderson said.
Or course, the roofing membrane, attachment method and adhesive choice are just part of achieving a hail-resistant roofing system. Stay tuned for our next post, which will discuss selecting the right coverboard to protect the membrane and insulation, and the right accessories to create a polished, professional-looking roof.
1 Source: U.S. Department of Commerce, Storm Prediction Center, National Weather Service. Accessed from the Insurance Information Institute at https://www.iii.org/table-archive/22795 on Sept. 18, 2020.
2 Source: National Insurance Crime Bureau based on an analysis of data from ISO ClaimSearch®. Accessed in “Facts + Statistics: Hail” from the Insurance Information Institute at https://www.iii.org/fact-statistic/facts-statistics-hail on Sept. 14, 2020.