Hail Damage Threshold Sizes to Common Roofing Materials

NOAA Standards

• Significant damage to common roofing materials occurs when hailstones have at least a 1-inch diameter, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). The NOAA changed its minimum standard for damaging hail for severe storm warnings in January 2010. Previously, damaging hail was reported during storms when hailstones had a 3/4-inch diameter, but experiments by the National Weather Service (NWS) caused the NOAA to increase the minimum diameter to 1 inch for such reports.

Hailstone Sizes

• NWS research shows that 3/4-inch hailstones -- which weather forecasters may refer to as "penny-size" -- usually don’t damage roof shingles. However, shingles that are at least 11 years old may be damaged by quarter-size, or 1-inch, hail. New and old shingles showed damage in experiments involving half-dollar, or 1 1/4-inch, hailstones.

Shingles

• Wood shake shingles and heavy composition shingles made of fiberglass and asphalt show signs of damage when struck by half-dollar-size hail, based on information from the Nebraska Department of Insurance (DOI). However, impacts from quarter-size hail may damage lightweight composition shingles. The Nebraska DOI indicates that 1/4-inch -- or dime-size -- hailstones can damage deteriorated shingles of any type.

Detecting Damage

• It's not always easy to determine if hailstones were large enough to damage your roof. Examine shutters, siding, wood fences and vehicles in your area for damage after a storm that included large hailstones. Your roof may need to be inspected if any of those items show significant signs of hail damage. In addition, check the ends of the downspouts around your home for an accumulation of granules that are the same color as your shingles. Significant granule loss may mean that hailstones damaged your roof.

Considerations

• Shingles that have cracks, blisters and curled edges may be showing the effects of hot temperatures and other weather-related conditions that aren't associated with hail damage. The Nebraska DOI notes that hailstones usually leave random strike marks, or indentations, on the surface of shingles. Take pictures of other items in your area that show hailstone strikes if you determine that hail damaged your roof, and you plan to file an insurance claim to pay for repairs. Photos of nearby structures damaged by hail can strengthen your claim with your insurer.