Evaluating Ballasted Single-Ply Roof Systems

“Stone-ballasted membranes constitute about 10 percent of all newly constructed built-up and single-ply roofing systems, and many older systems continue to perform well in the low-slope roofing market. Unfortunately, in their zeal some structural engineers have confused the smaller and lighter pea gravel used on built-up roofs (BURs) for fire and weather protection with the large size stones used as ballast on some single-ply roofing membranes.”