I have a basement slab, and a triple 2x10 backbone supported by steel columns. I've got a little sag in one which combined with other issues above, results in less than desired sag in the second floor (maybe a half inch).

Focusing on this part of the puzzle, the beam isn't sagging all that much, but i can see where it's bearing on the steel column it's smushed a bit at the bearing.

the basement is unfinished but would like to slowly finish it here and there, the first part being partition walls. it makes sense to put walls up along the underside of this beam.

Finally, the question: putting up such partition walls under the beam, what do i need to know about jacking the beam to give load to the partition walls to reduce the sag of the main beam? I understand the steel columns are on thick footings, but what's the word on spreading some load on the rest of the floor?

Bonus question: would it make sense to "sister" the steel column, putting a support just next to it so it's still on the footing to effectively add bearing(remember the smush?)


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    reinforcing sagging walls I would personally leave to the professionals. Any mistake you might make could have serious consequences.
    – depperm
    Commented Aug 27, 2019 at 12:40
  • "I've got a little sag in one" - one what? The steel columns? Or the 2x10s? If so, seems like you'd need a house jack to jack it up so you could replace it, or shim it. I'd agree with @depperm - you wanna be careful with this. I'm not sure I'd tackle all that myself, not being a professional contractor with this specialty. This sounds like it could be a dangerous situation if you don't do it right. I'd call in a foundation repair company. If you can correct the sag, why not just frame something around the steel columns, then cover with drywall? Commented Aug 29, 2019 at 15:41

1 Answer 1


I would add a steel plate to the top of the column to spread the load on the 2 X 10 s. Plate about 1/4 " thick or more , This will also compensate for the crush that has already happened. I have been able to find miscellaneous pieces of steel at a local weld shop at reasonable price. There should be some foundation under the concrete floor to support the steel column ; The floor itself can be very thin, I once found a 1 / 4 " thick spot in a basement floor concrete. So you can't just put a new column anywhere.

  • I agree , I have found homes that originally had no jacks. At some point one of the prior home owners added them, the slab was cracking at the center 2 of the 4 jacks. Ended up cutting a 36” square around the center jacks and digging a proper footing(I did add support while I had the jacks out) I later found out the builder met the minimum structural requirements and many people just added jacks without knowing that it would break the slab.+
    – Ed Beal
    Commented Aug 29, 2019 at 18:29

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