Abstract: An improved building structure is provided that is relatively inexpensive, easy to assemble and provides stable and sufficient shelter to inhabitants. The structure includes a plurality of support beams with each beam having an arch beam and a cross beam. The arch beam is in the form of a downward opening arch having first and second ends and defines radially inner and outer surfaces. The cross beam spans the arch and a loft may be supported on the cross beams. A skin is supported on the support beams forming the walls and ceiling for the structure. The skin engages the outer surface of the arch beam of each support beam and extends between the ends of the arch beam. End panels may be coupled to a support beam at either end of the structure to enclose the interior space.