Buildings requiring interior posts
Figure 11: Post-supported floors and mezzanines provide for more open floor plans.
When a building has interior columns, it is advantageous to use a post-frame building system for two reasons. First, it increases the likelihood that all building support elements will be on similar footings. This speeds construction and minimizes the likelihood of differential settlement. Second, interior posts may be more effectively incorporated into the framing system since they can be aligned with, and then connected via rafters or header beams to exterior posts to form rugged primary building frames (application 3, figure 7).
Interior posts are used in place of interior load-bearing walls, primarily because they provide for a more open floor plan. Money may also be saved by switching from bearing walls to posts, since posts utilize isolated footings which require less concrete than the continuous footings used to support bearing walls.
Interior posts are either used to support roofs in wide buildings (application 3, figure 7) or mezzanines (figure 11). In practice, wood-framed roofs that clearspan more than 90 feet and that are subjected to heavy snow loads will generally not be economically competitive with steel roof framing unless interior support is provided. Interior posts are seldom laterally supported between their base and crown, and thus are similar in design to posts in open exterior walls.