A great wheeled tiny house starts with a sturdy floor. We attached galvanized metal to the wheeled trailer and then framed the floor with 2 x 4's on 16-inch centers. Then, we insulated with 3 1/2 inch thick Styrofoam insulation. Every floor joist is bolted to the steel frame. Finally, we attached three-quarter tongue and groove plywood with glue and structural screws.