Porch footings

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dthornton

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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!
 
Check with your local building department. In Chicago it was 48" to the frost line. In SW Missouri it's only 18". I'm pretty sure the frost depth in Iowa is at 42".
 
If all you have is a porch, you could get away with a 12" sono tube to about 8" above the ground level. If you have a roof on it or maybe you will putting a roof on then you want to enlarge the bottom of the hole to about 18 to 20 inches. Pore the first 8" and then drop in the sono tube and don't forget the rebar. What ever the frostline is go a few inches below that and try to get all the loose dirt out of the bottom of the hole.
Leave rebar sticking up so you can tie the brick work to the post.
 
48" in Des Moines area. You may be a little less SW of me.
 
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