What Is a TPO Roof? How the System Works

TPO stands for thermoplastic polyolefin. It is a flexible, single-ply roofing membrane supplied in wide rolls. The membrane forms the exposed waterproofing layer of a low-slope roof assembly, above the supporting deck and insulation.

Single-ply describes the waterproofing membrane, not the entire roof. Beneath it, the deck provides structural support and the insulation helps control heat transfer. Some assemblies also include a cover board that creates a firm surface beneath the membrane. Each layer has a different job, and the complete assembly works together to protect the building.

During installation, sheets are secured over the prepared roof assembly and overlapping edges are joined with hot-air welding. Flashing connects the membrane around roof edges, walls, curbs, and penetrations. Together, these details direct water toward the roof drains and keep it outside the building.