The base test method provides a means of determining the load-carrying capacity of multiple spans, multiple purlin line standing seam roof systems. The method uses results from a single span, simply supported, two purlin line experimental tests, the 1986 American Iron and Steel Institute Specifications, and stiffness analysis of the actual design system. Currently, a base test must be conducted for each combination of purlins, deck panels, and clips that a manufacturer uses. The objective of this thesis is to investigate the possibility of eliminating the size of purlins, the orientation of purlins, length of span, and the presence or absence of insulation from a manufacturer’s required base test matrix. The findings of the investigation are based on the results of four different series of gravity load base tests. It was found that a linear relationship exists between the percentage of through-fastened capacity obtained by the purlins and their effective section moduli. This relationship was found to exist regardless of the purlin type. / Master of Science