With the growth of large sprawling urban and suburban areas in
hail-prone regions, the U.S. crossed the threshold of
billion-dollar hailstorms during the early 1990s. As a result,
manufacturers, insurers and testing laboratories have developed
test methods to evaluate the impact resistances of roof
The first test method to gain widespread use was UL 2218,
"Standard for Impact Resistance of Prepared Roof Covering
Materials," which uses the impact of a steel ball falling from
prescribed heights to establish performances of flexible roof
Although the UL 2218 test method has proved to be a good
measuring stick for the relative hail resistances of flexible roof
coverings such as asphalt shingles, the intense impact forces
imparted by the steel ball usually are too great for rigid roofing
materials, such as tile.
In response to this observation, in July 2005, FM 4473,
"Specification Test Protocol for Impact Resistance Testing of Rigid
Roofing Materials by Impacting with Freezer Ice Balls," which uses
an ice ball shot from an air cannon, was modified. With the
completion of that test standard, manufacturers now have two
options for testing the impact resistances of roof coverings though
it is expected UL 2218 primarily will be used for flexible roof
coverings and FM 4473 primarily will be used for...
To read the article in its entirety, please log in or register (registration is free).
Log in or register for FREE access to this article and other Professional Roofing online content.