Return to the Home Repair Forum | Post a Follow-Up

 o
Footings for Jack Posts in Basement?

Posted by molsonbc (My Page) on
Wed, Jan 9, 08 at 11:29

I'm planning on putting in 2 jack posts in my basement to slowly raise up a few joists to level in preparation to install a new support beam, but I was unsure about what sort of footing I should have for them. It's a concrete floor on a two story house, so I was thinking a couple of 4x4s on the floor would work.

And then when it comes time to install new permanent columns for the beam, I was unsure about footings for those, too. My thought was to cut a hole for each column, dig down 2 feet and use a little rebar and concrete to build up a footing. But I guess I wasn't sure if that was deep enough to dig. Any ideas about how much of a footing I should plan on?


Follow-Up Postings:

 o
RE: Footings for Jack Posts in Basement?

Ask your city/county what the code is and if you need a permit. If a permit is required (probably is) you don't get it, it will come back to haunt you when you try to sell down the road.


 o
RE: Footings for Jack Posts in Basement?

It's not only the depth of the footing, but also the size of the pad. A typical size footing would be two foot square and one foot thick. I would plan on supporting more than a few of the joists using two or three adjustable columns. As long as the concrete floor is at least a few inches thick, it should be ok for temporary.


 o
RE: Footings for Jack Posts in Basement?

If the posts are temporary then nothing of them will remain after the new beam is placed.

I usually use old sections of railroad tie about 5 feet long or a couple of layers of 2x12 to spread the load.
It does not have to be as good as a permanent footer for temporary use.

Permanent footers will need to meet the code for the load they will be carrying and the type of soil they rest on.


 o
RE: Footings for Jack Posts in Basement?

For the new footings, if your soil is undisturbed sand and gravel, and this is typical residential construction (nothing requiring engineering), than a 2 foot by 2 foot by 1 foot thick concrete (with steel rebar reinforcing) footer is generally sufficient. The top of the new footers should be about 6 inches below the top of the concrete floor in the basement. Again, this is for well drained, well compacted, sand and gravel, and typical non-engineered residential housing loads. If your specifics vary, it would be wise to ask a local soils engineer for specifics for your area.

If a permit is required, the AHJ will tell you how to do it.


 o
RE: Footings for Jack Posts in Basement?

It all depends on why you are jacking the floor joists. If it's just to take out a sag, and there's no load from a wall etc above, then a couple of 2 x 12's on flat are fine. Same holds for the permanent columns, if they are only carrying the weight of the floor above plus the live load and the new beam, there is no way they would ever punch through the existing slab, unless it is unrealistically thin. A cool way to take sag out of floor joists is to jack them straight and screw steel strips along the bottom edge, which is in tension when the beam (joist) is loaded. The load would then have to stretch the steel or shear the fasteners in order to deflect the joist. You could do every other joist.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Home Repair Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here