We had several 5' rolls of 2" chicken wire that we opted not to install in our metal building (the intent was the wire would be placed over the insulation to hold the insulation in--stays in fine without it). We went around the bottom with 1" chicken wire over the 2".
The top of the original run is covered in 2" wire, and the top of the 'expansion' run is covered temporarily with green plastic garden 'fencing'. If life ever slows down for a day for us, we'll cover the expansion with the 2" wire as well.
The expansion was built to keep chickens in, but not predator proof. We always lock the expansion at night so the girls can go out there until we open it up in the morning.