The design of metal building roof and wall systems under uplift and suction wind loading is complicated because the laterally unbraced purlin and girt's free flange is compressed, and the cross-section rotates due to the shear flow. The objective of this thesis is to introduce a Direct Strength Method (DSM) prediction approach for simple span purlins and girts with one flange through-fastened under uplift or suction loading. This prediction method is also applicable for the case when rigid board insulation is placed between the metal panel and through-fastened flange. The prediction method is validated with a database of 62 simple span tests. To evaluate the prediction for the case when rigid board is used, 50 full-scale tests with rigid board insulation are conducted by the author of this thesis. In the experimental study panel failure, connection failure and member (purlin and girt) failure are observed, and they all limit the system's capacity. Another important contribution of this thesis is that it builds the foundation for future study of a general, mechanics-based limit state design approach for metal building roof and wall systems that can accommodate uplift and gravity loads, simple and continuous spans, and through-fastened and standing seam roofs. / Ph. D.