Hail Impact Effects on the Wind Uplift Resistance of Fully Adhered Single-Ply Roof Membranes: Fid-Bau Portal

Hail Impact Effects on the Wind Uplift Resistance of Fully Adhered Single-Ply Roof Membranes

Donaldson, Justin / DeLeon, Marco / Savage, Kyle J.

Single-ply roof membranes are an increasingly popular roof covering for low-slope roofing applications. A common installation practice for these types of roof coverings is to fully adhere the membrane to a layer of polyisocyanurate (polyiso) insulation, using an adhesive between the top of the insulation and the underside of the roof membrane to bond these layers to each other. When a hailstone impacts a fully adhered single-ply roof system, it is possible for the impact force to result in a discrete fracture to the top facer/surface of the polyisocyanurate insulation. Such a fracture may cause a localized disruption in the bond between the membrane and insulation, which in turn, may collectively be suspected of affecting the overall wind uplift resistance of the membrane. This paper documents an investigation into the effects that hail impacts can have on the wind uplift resistance of single-ply roof membranes fully adhered to polyiso insulation. This effect is analyzed through laboratory testing of fully adhered single-ply roof system mock-ups using a negative pressure vacuum chamber. The tested mock-ups contained varying amounts of bond disruptions simulating the effects of hailstone impacts. The performance of these mock-ups in a negative pressure environment is then used to establish a general characterization of the relationship between the extent of hail-created bond disruption and any reduction in wind uplift resistance of the roof system. This relationship can be used in forensic evaluations of roof systems to aid in the determination of whether or not hail has compromised a roof system.