Novel free-standing open-span building frames for building construction and their use. The frames are assembled from base plates, upright posts, post-joist-rafter connectors, and a joist. Each base plate is a steel plate having an upper surface to which is welded the lower end of a steel post connector. The steel plates anchor bolt holes therethrough on each side of the post connector. The building has a steel reinforced concrete foundation with anchor bolts extending through the anchor bolt holes of each base plate, each base plate being secured to the anchor bolts with nuts. Each post has a lower end bolted to the respective steel post connector of the first and second base plate. Each post-joist-rafter connector comprises a post connector, a joist connector and a rafter connector. The first post has an upper end bolted to the post connector of the first post-joist-rafter connector, and the second post has an upper end bolted to the post connector of the second post-joist-rafter connector. The joist has first and second joist ends, the first joist end being bolted to the joist connector of the first post-joist-rafter connector, and the second joist end being bolted to the joist connector of the second post-joist-rafter connector. The frames are free-standing and can be spaced at distances of from 3 to 14 meters per frame.