New thermoplastic polyolefin (TPO) roof membranes have been extensively analyzed in laboratories, roof farm fields, and under accelerated weathering conditions. The ASTM International material standard for TPO membranes has been improved since its inception to incorporate more demanding tested-product performance, including requirements for accelerated weathering and aging.

Industry data on the aged performance of TPO roof membranes to date have largely been based on laboratory work, regional studies (such as the 10-year study by the Western States Roofing Contractors Association (WSRCA), and anecdotal case studies of field-installed TPO roofs—predominantly those that have been improperly designed and/or installed, and membranes with formulations that resulted in premature failure.

Today, there are TPO roofs in the United States that have been in service for nearly 20 years. This paper will review the long-term performance of a large sampling of field-aged TPO roof membranes installed throughout the United States by evaluating thickness, flexibility, inspection under 7X magnification, and aged seam and repair weld adhesion. The intent of this study is to evaluate 1) field-aged TPO roof membrane performance and 2) the ability to repair field-aged TPO roof membranes.