Hail—it is inevitable. In the contiguous 48 states, every state experiences hailstorms. And they are all too common in Hail Alley, which stretches from the upper Great Plains to Texas, from Montana to Florida. And, the hailstones are typically accompanied by high winds, which cause their own set of problems.
What can be done to mitigate hail damage to commercial roofs? A Neogard Elasta-Gard Aliphatic or Permathane Aliphatic II system is the solution. Easy to apply, and resistant to hail, wind, and degradation caused by ultraviolet exposure, our fluid-applied aliphatic urethane systems can handle the toughest weather. Neogard has systems available for all substrates, including built-up or modified bitumen, metal, single-ply, spray polyurethane foam (SPF), even concrete—which can sustain hail damage, especially if the concrete is old.
Before we get into the specifics of our aliphatic urethane systems, let’s look at some facts about hail and how it damages various roof substrates.
Hail forms when updrafts in a thunderstorm carry raindrops into very cold layers of the atmosphere. The raindrops freeze and sometimes collide, sticking together to create larger hailstones. The stronger the updrafts, the longer the raindrops stay aloft, and the larger the hailstones; they can range from the size of BBs, under ¼”, to the size or a softball, or 4 ½”.
Hail-producing thunderstorms occur in all the 48 contiguous states; they also happen in Hawaii, but are very rare in Alaska. The Great Plains states, Florida, Oklahoma, and Texas are at greatest risk, with Texas recording over 500 severe hail days from 2017–2019.
The cost of these storms is enormous. Multiple individual storms have caused well over $1 billion in damage. The Dallas-Fort Worth area has suffered two hailstorms which caused over $2 billion in damage in 2018 dollars: one in May 1995, and another in March 2016. Even a small, localized storm can cause serious property damage.
Hail and Roof Substrates
Hail can damage any roof substrate. Some are more susceptible to damage than others, and the signs of impairment vary. Hail damage may appear to be only cosmetic, but can create problems over time. Large hailstones can crack the surface, allowing water to enter the deck. That water can then flow into and undermine the structure underneath.
Concrete roof decks are least likely to suffer damage from hail. They are very durable and have high impact resistance. But, they can be damaged by large hailstones. If the concrete is old or has cracked, the implications can be more serious.
Built-up or modified bitumen roofs also can handle hail reasonably well, especially when surfaced with gravel. But hail can displace that gravel, leaving the underlying membrane exposed. Smooth-surfaced BUR/MB roofs are vulnerable to damage from hail greater than 1 ½” in diameter.
Metal roofs commonly sustain dents during hailstorms. These dents can be merely cosmetic; however, if the finish is cracked or chipped, the metal panels can rust, causing a shorter lifespan and weakening the roof’s integrity.
New single-ply membranes are resistant to hail. Thermoplastics like TPO and PVC can handle impacts from hailstones up to 1 ¾”, and EPDM—which is more flexible—can withstand up to 2 ½” hailstones. Aged thermoplastics do not do as well; hail as small as ½” can crack the membrane. Also, areas where the membrane is stretched, such as the perimeter or near rooftop equipment, are more sensitive to hail impacts.
Spray Polyurethane Foam (SPF)
SPF substrates can sustain cracks, dents, and punctures in a hailstorm, A basic SPF system, with the foam covered by a protective membrane, can withstand up to 1” hail with only a small dent in the surface, and no cracking. If the SPF is older, or the protective membrane is degraded, then the results can be more severe. The SPF may be exposed, leading to water entering the foam and damaging the roof structure. It can then also be degraded by ultraviolet exposure.
Neogard Aliphatic Urethane Roofing
A fluid-applied roofing membrane can help prevent hail damage to any roof, and provide other benefits. In particular, Neogard aliphatic urethane systems provide the best protection against hail, and have other desirable features.
Elasta-Gard systems are available for built-up/modified bitumen, concrete, metal, and single-ply roofs. Permathane Aliphatic II is specifically designed for SPF substrates. These systems use our 70620 urethane in the base coat, and 7490 aliphatic urethane for the topcoat. Those products have excellent elongation and tensile strength, allowing them to absorb hail impacts and maintain or return to their original shape, thereby protecting the substrate below. The Elasta-Gard systems use various primers specific to the substrate; Permathane Aliphatic II does not require a primer.
In particular, our Permathane Aliphatic II system has been tested to Factory Mutual’s FM 4473, “Specification Test Standard for Impact Resistance Testing of Rigid Roofing Materials by Impacting with Freezer Ice Balls.”
This test method simulates the impact of large hailstones on a roof. It uses ice balls in diameters from 1 ¼” to 2” launched against test panels of a roofing system which have prepared to FM’s and the roofing manufacturer’s specifications. If the surface does not crack after multiple impacts in the same area—within ½” of the target point—then the roof material is given a Very Severe Hail rating indicating how serious an impact it was able to withstand. The lowest rating is 1, meaning it did not crack when struck by 1 ¼” ice, to 4, which means it withstood impacts from 2” ice balls.
In addition to their hail resistance, our aliphatic urethane systems are resistant to degradation due to ultraviolet exposure, and can have a very long lifespan. They can also be applied over existing roof substrates or coatings, mitigating tear-off costs and environmental concerns.
And, both products in the systems are available in low-VOC -CA formulations suitable for use in jurisdictions with strong VOC restrictions—a factor which is now quite common. In fact, we recommend using our 70620-CA and 7490-CA as the default products for all our Elasta-Gard systems and Permathane Aliphatic II.
Hail is a constant threat to commercial roofs. However, a Neogard fluid-applied aliphatic urethane system can mitigate that threat. They will provide excellent protection against severe hail, and provide protection that will extend the lifespan of the roof, reducing maintenance and replacement costs. Find and contact your region’s Neogard Account Manager today.