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Low slope roofing systems are common on additions, garages, porches, and commercial buildings across the Midwest, and they present a different evaluation challenge than steep slope shingle roofs because the damage indicators are less visually obvious and the materials behave differently under impact. The three membrane types seen most often are EPDM, a black rubber sheet material, TPO, a heat welded single ply membrane usually white or gray, and PVC, another heat welded single ply that shares some characteristics with TPO but has different chemical composition and weldability. Each responds to hail impact somewhat differently, which matters when forming an opinion about damage.
Hail bruising on membrane roofing refers to a soft, compressed area where the granule or fiber backing beneath the membrane has been crushed by an impact, without necessarily puncturing the membrane surface itself. This kind of damage is not always visible from a simple walk over inspection and is often assessed by carefully checking the membrane at marked impact points, sometimes using a probe or by lifting a test area, to determine whether the underlying substrate has been compromised in a way that shortens the roof’s remaining service life even without an active leak.
Seam integrity is a central issue on any single ply roof, since these systems rely on heat welded or adhered seams between sheets rather than the shingle overlap pattern used on sloped roofs. A seam that has failed can be difficult to attribute definitively to a specific storm versus normal aging of the adhesive or weld, particularly on an older roof, and evaluating seam condition typically involves checking for consistent lift, separation, or cracking across a section rather than relying on a single isolated spot.
Ponding water is one of the more common points of disagreement on flat roofs. Some degree of ponding after rainfall is normal on many low slope systems and clears within a day or two as design intends; ponding that persists well beyond that and recurs in the same low spot generally points to a pre-existing drainage or structural deflection issue rather than storm damage, since a hail or wind event does not typically create a permanent low spot in the roof deck. Distinguishing a drainage issue that predates a storm from damage the storm actually caused, such as a punctured membrane or a blocked drain from storm debris, requires looking at the roof’s overall condition and history rather than treating standing water on inspection day as proof of anything by itself.
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.