The side porch on my 120+ year old house is sagging and will have to be rebuilt. It is attached to the house on the back side and the front side originally had 3 brick columns supporting it. Currently, one brick column still remains on one corner of the porch. The other corner is supported by concrete blocks, and the middle is held up by a couple of landscape timbers (!!). I want to rebuild the porch and return it as much as possible to its original looks. When I go to rebuild the brick posts, how deep should I put the concrete footings, and how big around or square should I make them? We live in SW Iowa, so it gets into the minus temps in winter. I don't know what the official frost line depth is here. Thanks!