If I was doing this in my yard I would make the footings for the columns about 18-24" square, a foot or so deep. One 1/2" vertical rebar is probably plenty but two won't hurt, put a bend in the down end. I would also run rebar in my footer between the columns, make that footer about 8" deep and a foot wide. poured as so columns and wall steel are connected and ends overlap a foot at least.
Last edited by 700LH; 04/13/10.
