Frank J. Foley, Jim D. Koontz and Joseph K. Valaitis
Viable roofing systems provide long-term waterproofing. Reinforced and non-reinforced PVC roof systems presence in the American low-slope roofing market spans the better part of three decades. This roof membrane brings particular unique features to owners of flat roofs -- significant energy savings from reflective membranes, solid performance in ponded conditions, inherent flame resistance, integral seam fusion, and ease of inspection, leak detection, and repair. However, in the American market of the mid-980s, a rash of catastrophic membrane shattering to aged, non-reinforced, monomeric-plasticized PVC roofs occurred. The reputation of PVC roof systems suffered. In response, non-reinforced roof system manufacturers discontinued these specifications and products in favor of today's standard, thicker, fabric-reinforced PVC roof systems. Currently, the Single Ply Roofing Institute (SPRI) organization reveals PVC thermoplastic roofing is once again in a growth mode in the United States low-slope roofing market.
However, the primary shattering characteristic, plasticizer migration, despite design improvements, remains a failure mode requiring definition and management. Hail, especially large hail creates catastrophic events, which, instantaneously (for instance the shatterings of the mid-80s) and completely undermines the positive aspects of this membrane system. To make matters worse, U.S. manufacturers expressly exclude hail events from their obligations to waterproofing performance, thus building owners shoulder the risk against this damage. Little direction if offered on aging and the need to monitor and replace aging, embrittled membranes. To draw a parallel: why provide attachment specifications if warranties exclude damage from all wind events when both wind and hail are naturally occurring events in the central heartland of the United States. Owners in these states need hail specifications and guidelines for timely replacements.
This research focuses on the relative aging and hail vulnerability of reinforced PVC membranes marketed in the 1990s by four prominent PVC manufacturers. The study centers on the sampling and testing of 87 membranes of various ages for plasticizer migration and hail simulation testing. The results indicate a dramatic range in test results between the best and worst of the four manufacturers. This paper targets roof owners, offering observations addressing membrane aging, monitoring and management.
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Posted on Tue, July 5, 2011
by CSR filed under