What Size Hail Can Damage a Roof?

NWS classifies a thunderstorm as severe when it produces hail at least 1 inch in diameter or wind gusts of at least 58 mph.[2] That criterion helps meteorologists describe a storm. It does not state that every roof under quarter-size hail is damaged—or that smaller hail cannot affect a vulnerable roof.

The object comparisons come from the NWS hail-size chart.[1] Estimate diameter with a ruler when it is safe, or use a credible storm report. Photographs without scale can make hail appear larger or smaller.

IBHS says a hailstone’s mass, diameter, and velocity determine its kinetic energy at impact. A perpendicular strike transfers more energy per unit area than a glancing impact.[3] Wind can alter velocity and direction, and repeated stones can concentrate impacts on one slope.

• Material: asphalt, metal, tile, wood, and slate fail in different ways.
• Age and weathering: field roofs have years of sunlight, heat cycles, rain, prior impacts, and maintenance history that brand-new test samples do not.
• Assembly: deck, underlayment, installation, fasteners, and what sits beneath a metal panel can change the response.
• Stone properties: hard, dense hail can transfer energy differently from soft or slushy hail of the same measured diameter.
• Angle and wind: one roof plane may take more direct impacts than another.

A storm map or neighborhood report establishes possible exposure. It cannot establish the condition, cause, or repair scope of an individual roof.

Asphalt shingles

IBHS identifies dents, tears or breaches, and granule displacement as asphalt-shingle impact modes, with severity varying by product and hail size.[3] In controlled testing, all new products tested with 1.5-inch laboratory hail received Good or Excellent performance ratings; 2-inch testing showed larger differences among products.[4] Those findings apply to tested new products under laboratory conditions—not every installed shingle.

Metal roofing

IBHS reports that hail can dent metal while current evidence does not show that dents alone reduce roof function.[3] Cosmetic appearance, coating damage, seam condition, and puncture or water-shedding performance should be evaluated separately.

Clay and concrete tile

Large hail may crack or shatter tile, with results varying by material, thickness, and impact location.[3] A laboratory impact-resistance class is evidence about a tested product, not a promise that natural hail below that class cannot cause damage.

Older and weathered roofs

Standard tests evaluate new materials, while installed roofs weather over time. Age does not prove that a mark came from hail, and ordinary granule loss, blistering, traffic, installation defects, and maintenance wear can resemble storm effects.

Assume a storm report estimates 1.5-inch hail, roughly a ping-pong ball. NWS size references support the diameter comparison.[1] IBHS testing supports a second fact: new asphalt products in that controlled test performed Good or Excellent against 1.5-inch laboratory hail.[4]

Neither fact answers whether a 12-year-old field roof was damaged. A useful review would document the roof material and age, which slopes faced the hail, wind direction, collateral marks, pre-existing wear, and close-up conditions. The conclusion comes from the inspection—not from converting 1.5 inches into an automatic repair or replacement decision.

Use the hail damage risk tool to organize those inputs, not to diagnose a roof or decide insurance coverage.

From the ground, look for fresh dents on gutters, downspouts, vents, flashing, or outdoor equipment; cracked skylights or tile; displaced material; and new interior water staining. Do not climb a wet, steep, or storm-damaged roof.

IBHS warns that missing granules alone do not mean hail damage and recommends using collateral evidence to help distinguish a hail event from normal wear.[5] Even collateral dents confirm exposure more readily than they confirm functional damage to every roof component.

A qualified inspection should examine each slope and vulnerable component and distinguish impact evidence from aging, wear, installation defects, and mechanical damage. Contact the insurer for policy and claim questions and use a licensed, insured local roofing professional for the physical roof assessment.

For valuation after damage is documented, see how roof depreciation works and the roof replacement cost calculator.