Pole barns usually have no solid foundation. Each post or pole is supported instead by an individual footing. A slab foundation is sometimes poured around the posts, once they are set. The footings are dug down up to half the height of the pole above ground. The bottom of the footing is filled with concrete, topped with loose earth back fill or gravel and topped with packed soil. Stick frame barns are built on traditional foundations. A stem wall is typically poured around the outside and may or may not have a concrete slab in its center.
Stick built barns frequently have concrete pad floors. The other options are wood frame floors suspended between horizontal ledger boards attached to the inside edges of the stem wall. These ledgers support traditional joists that are then covered with plywood decking or lumber flooring. Most pole barns have open dirt floors. Those with slab foundations have concrete floors. A system of flooring may also be built on top of the dirt, covering part or all of the barn floor with a raised platform.
Pole barns have horizontal braces starting with a piece of treated lumber at ground level known as the skirt board. The other braces are spaced evenly up the height of the wall and fastened to the poles. These are known as girts. The top of the wall is a beam, with one horizontal board bolted on the outside of the poles and one on the inside. Stick framed barns are built similarly to residential walls, with horizontal base and top plates and vertical studs running between them. The spacing is often relaxed from the required 16-inch to 24-inch centers.
Roof frames for barns are built in a variety of designs. There are two basic construction types. The first is traditional stick framing, built up of rafters, running from the top of the wall diagonally to a central peak supported by a ridge beam. In pole barns these are supported by long poles supporting the ridge. In stick framing, joists are run between the top caps of the side walls every 24 inches. Pole barns will have joists sometimes, but less frequently. The second framing method is prefabricated truss frames. A truss is built of upper cords, similar to rafters, and lower cords, similar to joists. Each frame is set in place between the tops of the side walls, typically spaced every 24 inches.