Re: steel pole in garage
Typically there should be a footing located under the slab for the post. This footing would be around 24" x 24" x 10" or 30 " x 30" x 12" poured concrete.with the post sitting on top and attached to this pad. The floor would be poured over top partially burying 3 or 4 inches ( depending on the thickness of the slab ) of this post.
If the bottom of the post is rusted under the floor and if there is any void between underside of the slab and the top of the footing then placing the post on top wouldn't be secure enough to withstand the weight from above.
Ideally it would be better to put up a couple of supports close by this post and remove the post. Then cut out the concrete around the area where the post goes into the concrete 3 inches from the center of the post on all sides .... in other words you end up with a 6 x 6 inch square down the thickness of the slab. Then drill a couple of holes to insert a couple of short pieces of rebar. Then build a form out of plywood having it higher than the slab by a few inches ( 3 or 4 or higher if you want ). Then fill the hole with bag premix of concrete and let it cure for 7 days.
The reason for it being higher than the floor is this becomes part of the footing but it keeps the steel post higher off the floor preventing the base to rust out.
Take the post you removed and have a base plate welded to the bottom with at least 2 holes drilled for the concrete anchor bolts that will be used to secure it to the new base.
Hopefully this makes sense and helps.
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