hello,
I have a 1924 cape, (story and a half) that has a 6×6 wood column in the basement that is getting a little spongy at the bottom. I want to replace it by jacking up on either side, cutting it out, digging a new 12″ square hole, filling the hole with concrete, then putting in a tapco mono post (15,000# compression strength). The 6×6 is about 5’8″ from top of floor to bottom of wood beam.
Does this sound resonable and prudent?
My concern is, what is the compression strenght of the 6×6 compared to the mono post?
I guess I am using the mono because I think it will be easier to install (threaded adjustment).
Any pointers or concerns would be greatly appreciated!
Thanks for reading my post.
Replies
I don't think you'll have any trouble. Jack the absolute minimum you need (1/2" or so), and do it gradually over 1-3 days so as to minimize any chance of cracking your plaster, etc.
Put some rebar in the concrete.
Sounds good except that the size of the footing depends on the load bearing capacity of the soils. The ecenter portion of a modest sized cape on that footing with good compacted stone/gravel is likeluy to be OK, but I'm not betting my breakfast that they did much to the soils in the cellar back in the twenties. I would opt for a larger pad, about 20" x 20" or so
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Hello Chuck,
I did a similar thing in my cabin. The center beam for the floor system (approx. 4x12) was supported by a single metal post (screw jack type lolly column) and was sagging by about 1.5 inches over 20 feet. Since I was finishing off the basement for living space I moved to a 6x6 cedar post (for aesthetics) in mid span. To do this I:
This worked great, except that I did all the jacking up over a couple of hours and when I was done a few doors upstairs were a bit stuck.
For your situation, I'd consider a 24"x24"X12" deep footing or bump-up to 32"x32"x12" deep depending on how much weight you are supporting. In the crawl space for my new house, the largest pier footing is 32"x32"x12" deep (for areas where two support walls intersected or were under jack studs supporting the upper floor loads), the smallest is 24"x24"X12" (in mid span of regular support walls)
Hope this helps,
Roger <><
Re the footing size, some clue can be taken from what's happened with the existing column. If it was just resting on a concrete floor (or maybe just a piece of stone), and it does not appear to have sunk significantly, then something in the 12-18 inch range is probably fine. The important thing is to take care to not disturb the soil that you DON'T excavate -- if you break up the soil, take it out and don't put it back. Then, just for a bit more security, use a hand compactor or some such to make sure the bottom of the hole is well-compacted.