A laboratory study was begun in 1983 to determine the long-term effects of hail on asphalt shingles. Simulated hailstones were launched at speeds of same-sized natural hailstones perpendicular to roofing panels constructed to replicate standard applications. Impacts were made on new fiberglass-reinforced three-tab, organic-reinforced three-tab, and fiberglass-reinforced laminated shingles at the beginning of the study and after approximately 11 years of natural weathering exposure.

This interim report is issued after 15 years of testing, which is a typical service life for many shingles in the southern United States.

The purpose of this study is to assess the effects of weathering on asphalt shingles impacted by simulated hailstones on new and weathered shingles. Shingle types tested included:

• 20-year-warranty, three-tab shingles with organic reinforcements
• 25-year-warranty, three-tab shingles with fiberglass reinforcements
• 30-year-warranty, laminated shingles with fiberglass reinforcements.

Findings and methods derived from observations throughout this study include the following:

• Identification of the characteristics of impact-caused damage to shingles.
• Documentation of the attributes of impact-caused fractures initially and after prolonged exposure to natural weathering.
• Evaluation of granule loss at impact locations to determine the effect of granule loss on expected shingle life.

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