Underwriters Laboratories Specifications for Impact Resistant Shingles
UL standard 2218 defines the performance characteristics of roofing products in terms of their ability to resist damage from extreme weather, wind, hail and flying debris typical of hurricane and tornado-like events. Roofing products that receive a Class 4 rating from UL under this general specification are considered to be the most hail-resistant asphalt roofing materials. UL maintains a current database of manufacturers whose products meet or exceed UL2218 Class 4 rating. Any of these manufacturers' certified products will provide the highest empirically verifiable performance with respect to hail and wind resistance. (see Resources)
How Roofing Materials Are Rated for Hail and Wind Resistance
In the laboratory, shingles are tested for impact and wind resistance by exposing them to a barrage of hail like particles, traveling at velocities similar to that of a hailstone falling through the atmosphere and reaching terminal velocity. This test does a good job of determining how a shingle stands up to a given amount of applied force. In the real world, however, the damage resulting from hail can be influenced by many factors that are difficult to account for in a standardized test, including ambient temperature, duration of storms, roof slopes and orientations, shingle surface contamination and poor construction techniques. Ratings must be taken as guidelines rather than guarantees.
Where Impact Resistant Roofing Pays For Itself
National insurers have published figures that show four states account for better than 40 percent of the hail damage claims in the United States each year: Texas, Oklahoma, Kansas and Nebraska. Hailstorms rival events like floods and earthquakes in terms of single event, all time largest payouts of damage claims, so many companies offer discounts on homeowners' insurance for impact resistant roofing materials, particularly in the most affected areas.
Hail and wind resistant shingles are not significantly different in installation procedures and requirements from ordinary asphalt shingles. In order to get the best wind resistance performance, it is recommended that shingles are applied using a six nail pattern, rather than the simpler three nail pattern used on lighter duty shingles.