Life-Cycle Costs of Commercial Roof Systems

The roofing industry in the United States generates annual revenues in excess of $23 billion. This represents a significant annual investment in infrastructure maintenance cost and the opportunity cost of these resources can significantly detract from an owner’s ability to invest in other areas. In addition, a failed or failing roof system represents a heightened opportunity for failure in the building envelope and inherently increases the risk of additional costs. Present roof asset management practice typically bases replacement decisions on fixed intervals, inspection results, maintenance issues, and, occasionally, failure risk. This paper develops a model for evaluating occupant costs and considering their impact in the roof management decision process through a total life-cycle cost (LCC) model that includes user/occupant cost model and correlates minimum total cost with improved intervention points in the asset deterioration cycle. The model is estimated from and applied to the extensive roof systems at Carnegie Mellon University in Pittsburgh, Pa. For these roofs, we find that the least cost roof service lives are roughly 30 years, but there can be considerable variation around this average for individual roofs.