Section 1504.7 Impact resistance. Roof coverings  installed on low-slope roofs (roof slope <2:12) in accordance with Section 1507 shall resist impact damage based on the results of tests conducted in accordance with ASTM D 3746, ASTM D 4272, CGSB 37-GP-52M or the “Resistance to Foot Traffic Test” in Section 5.5 of FM 4470.

Code Interpretation:
This code implies that all low-slope roof covering materials must be able to withstand typical impact loads, such as foot traffic, hail and driving rainstorms. All of these conditions are typical of what a low-slope roof covering will be exposed to throughout the course of the service life. Due to this fact, the referenced standard sets criteria for testing that is required of all low-slope roof material systems.

There are a couple of test methods and each method uses similar devices to test the material. The most common test method consists of dropping a dart, steel ball, or missile (ice), which weighs from 2-1/2 to 5 pounds (1.1 to 2.3 kg), approximately 4 to 5 feet (1219 to 1524 mm), on to the material and then evaluating the material for failure. Some hail tests now include projecting the missile (ice) from an apparatus onto the material set in vertical fashion.

It should be noted that these test requirements only provide impact resistance for typical impact – i.e. foot traffic, hail and driving rainstorms. If a roof system is to be exposed to further impact from building operations, further impact resistance must be provided.