With the introduction of single-ply...

With the introduction of single-ply roofing membranes in the 1970 low-slope commercial roofing quickly - and cleanly - polarized into an "either/or" market.
The choices appeared fairly clear sculpture Specifiers could opt for either the redundancy of the built-up arch (BUR) - made up of alternating layers of felt and bitumen - or the simplicity of the single-ply sheet; for BUR'S superior tensile vigor or single-ply's excellent elongation properties; for a field-built membrane or a single prefabricate as halt and coal tar bitumen or synthetic rubbers and plastics. The