TPO single-ply membrane roof systems have been installed in the U.S. since the early 1990s. Although TPO membrane manufacturers produce membranes in various thicknesses, 45-mil-thick TPO membranes are used in a vast majority of installations and have become the default membrane thickness for most specifications. This raises a question: Is thicker better?
Review of manufacturers' product literature reveals most TPO membrane manufacturers produce 45- and 60-mil-thick TPO membrane products. Several manufacturers also produce 72- and 80-mil-thick TPO membrane products.
Although TPO membrane manufacturers offer products of similar thicknesses, some manufacturers differ regarding where they place the reinforcement within their membranes' cross-sections. The dimension referred to as "thickness over scrim" indicates a reinforcement's placement and identifies the amount of membrane material above the reinforcement that is exposed to weathering and provides waterproof integrity.