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Performance Approach to the Development of Criteria for Low-Sloped Roof Membranes.

pdf icon Performance Approach to the Development of Criteria for Low-Sloped Roof Membranes. (3017 K)
Rossiter, W. J., Jr.; Frohnsdorff, G. J. C.; Masters, L. W.; Martin, J. W.

NISTIR 4638; 36 p. July 1991.

Available from:

National Technical Information Service
Order number: PB94-160751


evaluation; low-sloped roofing; membranes; performance criteria; requirements; roof functions; roofs; seams; test methods; watertightness


This report outlines a performance approach for developing criteria for the selection and use of membranes in low-sloped roof applications. An overview of previous efforts for applying the performance approach to membrane roofing is also given. A fundamental aspect of the performance approach is that selection criteria are based on an understanding of the requirements necessary for the membrane system to perform acceptably in service. The availability of performance-based criteria would greatly assist in eliminating some of the defects that have plagued low-sloped roofing over the years. The approach consists of seven steps including identification of the key functions to be performed by a roof, identification of attributes essential to satisfactory performance, development of the requirements, criteria, and test methods, and putting in place a feedback mechanism to revise the criteria, if warranted, as new information becomes available on the performance of the system in service. Five key functions associated with the performance of the membrane in a low-sloped system are identified, and performance requirements for each function are proposed. These functions are watertightness, maintainability, health and safety, environmental impact, and appearance. Of these five functions, watertightness is the one that directly affects the major problem (i.e., leaks) associated with low-sloped roof performance. As a consequence, the majority of the requirements recommended for membrane systems in past studies, as well as in the present report, emphasize this aspect of performance. It is recognized that considerable effort may be needed to develop criteria and test methods for the complete set of attributes. Consequently, the initial work should focus on those attributes of membrane roofing that have been associated with the most problems. Review of data from NRCA's Project Pinpoint indicated that seam defects in single-ply membranes have been the problems most frequently enountered for these types of roof systems. On this basis, it is further suggested that the application of the performance approach to membrane roofing begin with the subject of seams. As an initial step in this direction, an outline of the needed criteria is presented including attributes and suggested requirements. The development of criteria and test methods are reserved for future study.