The NRCA Roofing and Waterproofing Manual, Fifth Edition, contains reroofing guidelines for steep- and low-slope roofing. The August 2004 issue of Professional Roofing featured an article that discussed the steep-slope text of the manual (see "Steep-slope reroofing considerations," page 28). This article focuses on the low-slope reroofing section.
NRCA defines low-slope roof systems as a category of roofing that includes weatherproof types of roof systems installed with slopes less than or equal to 3-in-12 (14 degrees). Because each roof system is unique, it is not practical to address every condition that may be encountered during a reroofing project. The manual's reroofing section provides information applicable to many conditions commonly encountered during a reroofing project.
Low-slope roof assemblies typically are composed of a roof membrane, roof insulation, vapor retarder—when built in—and roof deck. Together, a roof membrane—including surfacing, insulation and vapor retarder—are considered a roof system. A roof system plus a roof deck are considered a roof assembly.