Retrofit single-ply roof systems (RSPRS) are increasingly being used to re-cover existing structural metal panel roofs. One of the primary concerns when an RSPRS is installed over a structural metal panel roof is wind uplift. Of significant concern is when an RSPRS is mechanically fastened into every other purlin instead of every purlin. The “every other” type of installation changes the wind-resistance load path of the metal building. This every other load path seemingly doubles the load on the purlin-to-main-frame connection for the purlins to which the RSPRS is attached.
ASTM E1592 physical testing has been performed on three test roof assemblies—each consisting of a mechanically attached TPO with flat stock and flute-fill polyisocyanurate over a 24-in.-wide structural metal panel roof system. Each RSPRS has different fastener patterns, which resulted in different wind uplift resistance values. The tests were heavily monitored to obtain deflection measurements and stress/strain information for multiple components within the assembly.

The results from an analysis of the three physical tests will be presented. The results from physical testing (small and large scale) were used to develop finite element analysis (FEA) modeling of alternative fastening patterns, and these conclusions will be presented.