Living Unit Floor/Porch
This is a rectangular frame with 2x4 joists at 16" centers, topped with 5/8" plywood. Use 16D nails to frame this and attach the 2x4's with two nails at each connection. Sheath the frame in 5/8" (19/32") plywood on one side. Use small nails for this such as 8D, 6D, or 4D nails. The porch should be painted, since it will be exposed to the elements.