The objective of the Standing Seam Roof Systems Research Project at the Virginia Polytechnic Institute and State University is to develop a design procedure for the strength of Z-purlin supported standing seam roof systems under gravity leading. Various approaches were taken to calculate the strength of systems with either torsional restraint, third point span restraint, or midspan restraint. Since few test results are available for single and three span continuous, two purlin line systems, the primary focus of this research is analytical. Even though the test setup used for these tests does not represent actual field conditions, the data obtained will be extremely useful in the development of analytical models to predict system strength. However, at least four multiple purlin line tests will be required to verify the accuracy of the design procedure. The analytical formulation will include the effects of sliding friction in the clips and "drape" restraint effects of the standing seam deck.