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Old 05-30-2007, 07:14 AM   #1
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Jacking main beam/floor joists

Hi Guys, newbie (to the forum) here, and I'm working on renovating an older house (1920). The main beam was built to span a 25'x30' foundation lengthwise (roughly). Floor joists were cut with a tonge on the end where they tied into the main beam, and they rest on a rough cut 2x4 ledge. Floor joists have cracked along the tongue and caused the floor to sag. I'm in the process of gutting all the walls (plaster and lath). Once complete, I plan to support the main beam with lally columns and jack each joist back into place, then support with joist hangers. Currently the main beam has jack-posts supporting it. Any suggestions for the best way to make footings for the lally colums? Also, any pitfalls I should look out for in supporting the floor joists? Thanks.


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Old 05-30-2007, 08:17 AM   #2
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Originally Posted by gshock View Post
.... Any suggestions for the best way to make footings for the lally colums?
The kind of soil that is under the area has an impact on the size and depth of your footings. Thus, you could go minimum size of 1'-0" down x 2'-0" square or you could go 3'-0" x 3'-0" square or more. You should look into this and check with your town or a soil engineer.

Originally Posted by gshock View Post
....Also, any pitfalls I should look out for in supporting the floor joists? Thanks.
None, off the top of my head. This is really factored by what can be visually seen and inspected - on site.
Tips: When jacking, go S-L-O-W-L-Y and listen for any unusual noises; cracks, pops, etc. You are not just jacking up that floor, you will be jacking up everything above that beam, including the 2nd/3rd floors if you have these. If you have any ceramic tile floors above the area, they will end up cracking as you raise the beam and the joists attached to it. If the joists are attached onto the sides of the main carrying beam (as opposed to sitting on top of it) I would advise that you attach your joist hangers prior to jacking as the joists WILL pull away from the beam once you start jacking it up.

Ultimately, I would suggest that you have someone knowledgable about structural design out to your house to inspect the area and review what your plan is....just to make sure that you are not missing something.

FWIW-If we are in a complex remodel or need to make a complex design change, I ALWAYS get a 2nd or 3rd review from an experienced fellow GC or engineer, before undertaking any major structural mods/changes.


- Build Well -

Last edited by AtlanticWBConst.; 05-30-2007 at 08:20 AM. Reason: spelling
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