Hail Damage to Roofs

Hail forms when thunderstorm updrafts carry raindrops into air cold enough to freeze them; the stones grow as supercooled droplets freeze onto them and fall once they are too heavy for the updraft to support. Roofs, being the most exposed surface of a building, take the brunt of hailstorms, and hail is one of the largest sources of residential property insurance claims in the central United States.

Size, speed and severity

The US National Weather Service treats hail 25 mm (1 in) in diameter, about the size of a quarter, as severe. Estimated fall speeds, which are uncertain, range from roughly 14-40 km/h (9-25 mph) for stones under 25 mm to 71-116 km/h (44-72 mph) for 50-100 mm (2-4 in) stones; the largest stones may exceed 160 km/h (100 mph). The US record hailstone fell at Vivian, South Dakota on June 23, 2010; it measured 20 cm (8 in) across and weighed about 0.88 kg (1 lb 15 oz).

Frequency and losses

NOAA's Storm Prediction Center recorded 5,373 major hail events (stones 25 mm or larger) in the US in 2024 and 5,432 in 2025, according to the Insurance Information Institute. Texas had the most in 2025. One large US insurer alone reported paying more than $5.6 billion in hail claims in 2025.

How different roofs are damaged

Damage thresholds vary widely by material, thickness, age and the substrate beneath. Industry summaries give approximate figures:

• Asphalt shingles: standard products may show functional damage (fractured mat, granule loss exposing asphalt) from about 32 mm (1.25 in) hail; impact-rated products resist larger stones when new.
• Wood shakes: splitting is common from about 38 mm (1.5 in) hail.
• Slate: thinner slate can crack from 25-38 mm hail; thicker slate performs better.
• Concrete and clay tile: cracking becomes widespread at larger sizes, around 50-75 mm (2-3 in) and above.
• Metal panels: usually dented rather than punctured, even by very large hail; dents may be cosmetic or may affect coatings and seams.
• Low-slope membranes: thin single-ply sheets over soft insulation can puncture from moderate hail, while thicker membranes over a cover board resist much larger stones.

Assessing damage

Inspectors distinguish functional damage (which shortens service life or allows leaks) from cosmetic damage (appearance only). Insurance policies in some US states treat cosmetic metal dents differently from functional damage, so endorsements matter.

Reducing risk

Options include impact-rated coverings (UL 2218 or FM 4473 Class 4), thicker or reinforced membranes, cover boards under low-slope systems, and timely replacement of aged roofing, since weathering makes many materials more brittle. Research by the Insurance Institute for Business & Home Safety (IBHS) uses field-measured hailstone properties to develop more realistic test methods.