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Assessing hail damage on a commercial roof looks quite different from doing the same on an asphalt shingle residence, largely because commercial membranes come in so many forms. TPO, PVC, EPDM, modified bitumen, and built-up roofing all respond to hail impact differently, and metal panel roofs respond differently still. A protocol that works for identifying bruised shingle mat will not translate directly to a single-ply membrane, which is why organizations such as the National Roofing Contractors Association and testing bodies like Haag Engineering have developed separate guidance for evaluating impact damage on low-slope commercial systems.
On single-ply membranes, assessors typically look for fractures, splits, or punctures at the membrane surface, along with displaced or cracked ballast on ballasted systems and dislodged granules on cap sheets. Test squares, small marked areas where hail hits are counted and measured, are often used to establish a hit density across the roof, which helps determine whether damage is scattered incidental impact or a pattern consistent with a significant hailstorm. On modified bitumen and built-up roofs, evaluators check for fractured granules embedded in the surfacing and, where warranted, cut small samples to examine whether the impact reached the underlying felt or bitumen layers rather than remaining cosmetic.
A central distinction in any hail evaluation is between damage that is purely cosmetic and damage that affects the roof’s function, meaning its ability to shed water and resist further weathering. A dented metal panel might be cosmetic if the coating and seams remain intact, while a fractured membrane at a seam is functional because it creates a path for water intrusion. This distinction matters for scope and pricing, and it is one reason experienced assessors document findings with detailed photographs, measurements, and sometimes core cuts rather than relying on a visual pass alone.
Because hail can also be confused with mechanical damage from foot traffic, equipment dragging, or age-related surface cracking, protocols generally call for examining impact marks for consistent directional patterns, checking exposed metal for the round dish-shaped dents characteristic of hail versus the linear marks of mechanical contact, and cross-referencing storm data for the date and hail size reported in the area. None of this changes the fact that determining what is covered under a given policy remains a separate question from documenting what physically occurred on the roof.
Roof age and repair history also factor into a hail assessment, since areas that were previously patched or that carry old seam tape and adhesive squeeze-out are sometimes more susceptible to a breach from an impact that a fully intact section of membrane would have withstood without incident. Trained assessors typically note these prior repair locations separately from new storm-related findings, since treating an old patch failure as new hail damage, or the reverse, would misstate the actual scope. Wind uplift performance, which relates to fastening patterns and cover board attachment rather than impact resistance, is a related but distinct consideration that sometimes comes up in the same inspection when a storm event included both hail and significant wind.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.