Steel-Kits's standard framing packages are designed to be built over a slab floor. If you want to build over a basement, crawlspace, or stem wall, you will need one of our optional steel floor-joist systems. Steel-Kits has a specially designed floor system for each of our home models that includes a steel support beam and heavy-gauge floor and rim joists. The system is engineered for standard residential loads up to two stories and is intended to support the floor decking of living space only. It is not designed for heavy-duty loads like cars and boats and cannot be used to support the flooring of a garage.