Thermoplastic Polyolefin (TPO) is a single-ply roofing membrane made from polypropylene and ethylene-propylene rubber polymerized together. It is an alternative to PVC and EPDM that is typically more cost-effective and carries the same warranty. The overlap of the sheets is heat-welded using hot air machines to create a watertight bond. The sheets can be either mechanically fastened or fully adhered to the substrate. TPO membranes deliver a pliable and durable sheet with excellent weathering characteristics and resistance to harsh chemicals and industrial pollutants