Factors Affecting the Service Life of Seams of EPDM Roof Membranes
Walter J. Rossiter Jr, Jonathan W. Martin
A quarter century ago, a revolution occurred in the U.S. low-sloped roofing industry with the introduction of a number of new membrane products including elastomeric and thermoplastic polymeric membranes and polymer-modified bituminous membranes. Today, these membranes account for over two thirds of the total low-sloped roofing market in the United States. One single-ply membrane, EPDM (ethylene-propylene-diene terpolymer), gained wide acceptance in that it captured about one-third of the total low-sloped roofing market by the mid-1980s. Also by the mid-1980s, however, surveys conducted by the U.S. National Roofing Contractors Association (NRCA) began to indicate that the EPDM seams were failing leading to roof leaks. These seams were fabricated in the field using liquid-applied polymer-based adhesives. Due to the economic importance of EPDM roofing, the high costs associated with leaking roofs and, most importantly, the urging of the contractor segment of the roofing industry, NIST initiated research to elucidate the factors affecting the service life performance of EPDM seams. The majority of this research was conducted under the auspices of an industry-government consortium. This paper presents a short overview of the NIST experimental findings. At the beginning of the research and in collaboration with industry, NIST attempted to identify the most likely application, design, material, and environmental variables affecting seam service life performance. From this list of over two-dozen variables, the contribution that each variable made acting alone or in combination was assessed through statistically designed creep-rupture experiments. Outcomes of these experiments included the identification of the mostimportant variables affecting seam performance and the derivation of a mathematical model for linking field and laboratory seam joint responses. The results of these experiments lead to recommendations for improving the service life performance of seam joints. These recommendations were readily adopted by industry and contributed significantly to the improved the performance of EPDM seams. Today, EPDM seams fabricated with tape adhesives and the service life performance of these tape-bonded seams are routinely acknowledged by industry as being quite satisfactory.
April 17-20, 2005
Lyon, 1, FR
Durability of Building Materials and Components Conference
building technology, creep-rupture testing, EPDM roofing, seam adhesion, service life prediction