Analyzing self-adhering underlayments
Differences between products and product performances cause concerns
Self-adhering polymer-modified bituminous sheet underlayments enjoy widespread acceptance and use in the U.S. roofing industry. According to The 2005-06 NRCA Steep-slope Roofing Materials Guide, nine manufacturers produce 21 self-adhering polymer-modified bituminous sheet underlayment products.
NRCA and many roofing professionals recognize there are considerable differences among some self-adhering polymer-modified bituminous sheet underlayments. To better understand these differences, NRCA performed a limited analysis—including laboratory testing—of self-adhering polymer-modified bituminous sheet underlayments. The results of the analysis may surprise you.
Self-adhering polymer-modified bituminous sheet underlayments offer considerable advantages over alternative means of providing waterproof membrane underlayments for steep-slope roof systems. For example, before the development and widespread acceptance of underlayments, underlayments for ice damming areas on steep-slope roof systems typically consisted of applying two layers of organic felt in solid troweled applications of roof cement. The use of self-adhering polymer-modified bituminous sheet underlayments for this application provides a substantially cleaner application in a single labor-saving application.
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