Single-ply thermoplastic membranes consist of flexible sheet materials that are used in one-layer configurations as low-slope roof membranes and can be either mechanically fastened along the seams or fully-adhered to an underlying cover board or board insulation. While manufacturers have proprietary material composition for membrane roofing, the most commonly used thermoplastic membrane materials are thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC). Currently, these membranes are among the most common roof coverings used for low-slope roofing on new buildings and are also commonly used in re-roofing to cover or replace other roof types. Figure 1 shows a typical TPO roof membrane in a low-slope application.
Figure 1. Low-slope installation of a single-ply thermoplastic membrane.
In Nelson’s experience, thermoplastic roof membranes perform quite well during wind events, including hurricanes. The strength of the membrane materials is such that the membranes and the properly heat-fused seams do not readily fail when exposed to typical uplift forces associated with wind. When wind-related uplift failures do occur, they typically begin from the attachment at the edge of the roof (Figure 2) or are related to failures of the fasteners for the membrane or the insulation below (Figure 3). Fasteners that are not fastened into or through a proper deck/substrate can be especially problematic when loaded in uplift. Even when such failures do occur, substantial or complete removal of the single-ply membrane is rare.
Figure 2. Missing cap flashing at roof perimeter and displaced single-ply membrane following Hurricane Hanna (2020).
Figure 3. Failed, loose fasteners for insulation below TPO membrane roof following Hurricane Ian (2022).
Because single-ply membranes consist of only one layer and are relatively thin compared to other roof coverings, they can be susceptible to damage from wind-borne debris during hurricanes (Figure 4). An evaluation for a pattern of gouges, slices, or punctures from wind-borne debris is often part of the assessment of these membranes after a hurricane event.
Figure 4. Puncture in a TPO membrane determined to be from wind-borne debris.
Nelson’s team of professionals has extensive experience evaluating all common roof coverings, including single-ply thermoplastic membranes, following hurricane and other windstorm events. We stand ready to assist our clients with the evaluation of roofs and other building components following the recent Gulf- and East-coast storm events.
