Most horse barns today are post-frame buildings, so the “side walls” are 6-by-6 inch columns spaced from 8 to 12 feet apart depending upon the design of your building. Horizontal boards (“girts”), typically 2-by-6s, are nailed to the outside of these columns to strengthen the frame and attach exterior siding. Depending upon the width between columns, side walls may need extra framing to support stall lining.
If you are building a beam and rafter barn, beams are attached to the tops of columns to support the roof framing; however, for most bigger barns, pre-manufactured roof trusses are lifted into place by cranes and secured to the anchored foundation columns.