Hail vs SPF – Will a Spray Foam Roof Hold Up?
Hail is a significant concern for commercial roofing. Here's how spray polyurethane foam performs under hail impact.
Why Foam Is More Hail-Resistant Than Sheet Membranes
Sheet membranes (TPO, EPDM, modified bitumen) are relatively thin and can be punctured by large hail. The underlying insulation boards don't absorb impact — the impact force is transferred through the membrane to the hard board beneath, concentrating stress at the impact point. Spray foam is different: its cellular structure absorbs and distributes impact energy rather than concentrating it. The foam "gives" slightly under impact and recovers, distributing the force across a larger area.
What Happens During Hail Impact on Foam
Small to moderate hail (under 1 inch): typically causes no damage to the foam or topcoat. Moderate hail (1–2 inches): may cause surface indentation in the topcoat without penetrating to the foam. Large hail (2+ inches): can penetrate the topcoat and potentially damage the foam surface — requiring repair.
Repairing Hail Damage
Topcoat-only damage: apply compatible coating over the damaged areas. Foam surface damage: clean, apply compatible sealant or new foam, recoat. Most hail damage is cosmetic or minor — the repairability of foam roofs is one of their practical advantages over sheet membranes where hail punctures can be more serious.
Insurance Considerations
Hail damage to commercial roofs is a common insurance claim. Document hail events and inspect for damage promptly. Minor damage that goes unrepaired can lead to larger issues over time.