Of interest: Check out Pioneer Homes Photo Page
Step 5: The Second Floor
If you have a second floor or loft, you can hang it directly off of the wall. Nail or screw 2×8 or 2×10 nailing strips onto the wall, and attach joist hangers to the strips.
Place the joists in the hangers and proceed with the deck, which can be a variety of materials including plywood, card decking, or other.