Hail Resistance of Roofing Products,

A test was developed for evaluating the hail resistance of roofings, in which synthetic hail-stones ice spheres of various sizes were shot at roof assemblies at their free-fall terminal velocities. Indentations, granule loss and roofing fracture were observed. The following conclusions have been made from these results All roofing materials have some resistance to hail damage, but as the size of the hail increases, a level of impact energy is reached at which damage occurs. This level lies in the range of 1 12 to 2 inch 3.8-5.1 cm hailstones for most prepared roofings. Because of the ways in which prepared roofings are applied, most products have areas of different vulnerability. The solidly supported areas of roofing tend to be the most resistant to hail damage. Heavier shingles tend to be more hail-resistant than Type 235 shingles. Weathering tends to lower the hail resistance of asphalt shingles. Built-up roofs on dense substrates tend to resist hail better than those on soft substrates. Built-up roofs made with inorganic felts tend to be more hail resistant that those made with organic felts. Coarse aggregate surfacing tends to increase the hail resistance of roofing