Hail Damage to a Commercial Roof, whether its Modified Bitumen, Metal, BUR, TPO, or SPF Foam Roofing is very different then the damage to a conventional asphalt shingle. It takes a trained, experienced professional to inspect and analyze to overall damage and come to the right conclusikon.
Unlike a traditional Fiberglas residential shingle which has a Fiberglas based mat, Modified Bitumen uses a polyester mat. Modified bitumen is a roofing membrane consisting of asphalt and plastic or rubber polymers, and is therefore widely considered an evolution of asphalt built-up roofing (BUR). This roof system has two types: atactic polypropylene (APP) and styrene-butadiene-styrene (SBS). The SBS is the most common, boasting highly flexible membranes, giving it stronger expansion and contraction capabilities. Its more resistant to hail then shingles, but can still be damaged.
Built Up Roofing (Tar and Gravel):
Built up roofs with gravel typically do not sustain any damage until the hail stones exceed 2" in diameter.