Impact Resistance Testing for Roofing Materials

Using roofing materials that are impact resistant is the most effective way to minimize hail damage, especially if you live in an area that experiences multiple hail storms per year. Within the last 25 years, industry standards were set for roofing materials giving class ratings for impact resistance. In 1996, a test known as UL 2218 was developed. In this test, steel balls of various widths are dropped from 12-20 feet onto prepared roof covering materials. The test simulates the impact energy of free-falling hailstones.

The balls are dropped twice in the same exact location. Then the material is carefully examined for evidence of damage; the material’s exposed surface, back surface and under layers must be free of any cracking, rupture, or fracturing in order to gain an impact resistant classification.

For example:

Class One: shingle can withstand impact from a 1 1/4″ steel ball
Class Two: shingle can withstand impact from a 1 1/2″ steel ball
Class Three: shingle can withstand impact from a 1 3/4″ steel ball
Class Four: shingle can withstand impact from a 2″ steel ball

Another test known as FM 4473 is also an industry standard test used for more rigid roofing materials such as clay, concrete or slate. In the FM 4473 test, ice ball missiles are fired through a special launcher at a prepared roofing assembly. The test is meant to simulate the impact energy of an actual hail stone. Again, class ratings are given for impact resistance, with Class 4 being the best possible rating.

When shopping for a high quality roofing material, consider using a Class 3 or Class 4 rated roof covering in accordance with UL 2218 or FM 4473 testing. Just because a material may look durable, don’t be deceived. Make sure to read the label for more impact resistant information.