Purpose Many factors play a part in the service life of a roof. Some factors are uncontrollable. Others can definitely be controlled. There are some aspects of roof degradation that will follow a recognized path and the end result can be predicted. The normal degradation of a built-up roof begins at the top surface. This is understandable since it is the top surface that is subjected to the deleterious elements of the atmosphere. As soon as a roofing bitumen is exposed to these elements, an age hardening process begins. As the softening point of the bitumen increases, cold flow properties diminish, alligatoring increases and resistance to moisture penetration decreases. The volatizing or subliming of a roofing bitumen takes its toll on the performance characteristics of the bitumen. At some time prior to the roof reaching the point when maintenance is no longer feasible, preventive maintenance should be established, even though the roof may not be leaking. After considering the age, type of bitumen used to construct the roof, and general condition, the use of Koppers Roof Resaturants offers an effective means of implementing preventive roof maintenance.  Return to Effective Maintenance with Tar and Asphalt Roof Resaturants