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1victorianfarmhouse 12-09-2012 02:38 PM

Jackinig Up Sagging Joists
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One side of the kitchen floor near the basement stairs is sagging and has been for many years. This is because the main vertical support post on that side was anchored in concrete, and rotted over the years. There is about a 3/8" difference in height between the right and left sides of the doorway seen in the picture.

I have removed the rotted post and have a temporary post in place holding it up. I would like to put a steel I-beam in place under the joists with a jack and post under each end to jack it into place gradually. The I-beam would be 78" long, 4" wide, and 5" high. In the picture the beam would run along the white board in the picture from the joist near the gas line and continue past the hard to see white joist near the bottom of the picture and end at the joist at end of the stairway. Does this sound like the correct thing to do?

I can get the I-beam and columns easily enough, but the jacks are my question. What types of jacks should I look for that I can gradually adjust that will be strong enough to actually lift the house a few fractions at a time until I have it level??

There is already some cracking in the walls, so that's not an issue.

As always, thank you very much!


Wuzzat? 12-09-2012 03:10 PM

Based on the original cross sectional area of the rotted wood post you can figure how much downward force it was resisting. The Engineering Toolbox site can help you with this.

nealtw 12-09-2012 09:58 PM

Your biggest deal will be the floor, you need footing under both posts. You need to figure live and dead loads and figure how much more it will take to lift it and then you can figure how big the footings need to be. Will the cast iron pipe be in the way of the footing?

1victorianfarmhouse 12-09-2012 10:37 PM

The rotted post was a 4x6, probably some type of pine, it's definitely not oak, poplar or maple. I need to do more research on the Engineering Toolbox site to figure out the downward force it was resisting. Of course, it's entirely possible it wasn't the correct size for the job.

The concrete floor looks to be at least 6" thick. Figuring the live and dead loads are entirely new to me, and will take some time for me to learn and figure out. I was originally thinking of having a steel pipe with ends made to fit between the I-beam and the floor once it has been jacked up to level.

Additional comments are very welcome!

The cast iron pipe will not be in the way of the footing, but may require some minor notching of one side of the I-beam.

nealtw 12-09-2012 11:33 PM

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I ment new footing in the floor.

svoelkel 12-10-2012 08:22 PM

Here is an explanation of how to add a new footing within an existing slab like the one pictured above.

That web site has several other articles in their archives that may be helpful to you.

In my project, I used temporary adjustable jack posts from a big box store to hold the load and bottle jacks to lift. Move it up slightly with the bottle jack and tighten up the adjustable jack post to hold it until the next time you lift it (I have 8 of these slightly used and for sale in Atlanta if anyone needs some). Have a partner extend the post as you lift with the jack or one will come loose and split your skull. I did have a structural engineer confirm the load vs. the capacity of the temporary jack posts for my job but if the load was held by one 6"x8" post that you are replacing with two temporary and then two permanent posts, it is likely that one of these 12,000lb capacity jack posts at each end of your beam will be adequate followed by a 6x6" permanent post at each end. But I speak sacrilege, get an engineer to confirm this so you don't die in the process. Most important is to open the slab and pour footings. If you put the new columns on the slab, you will likely be repeating the job in a few years.

svoelkel 12-10-2012 08:27 PM

I also meant to suggest that channel iron might be an alternative to an I beam. It might be easier to work with and easier to secure to the beam you are raising.

1victorianfarmhouse 12-10-2012 09:18 PM

Thanks Neal and svoekel!

I did some Googling last night and found some info on the footings, but the Hammerzone link looks like the perfect how-to. I'll be visiting with a friend who is a general contractor soon, he'll be able to recommend an engineer.

This side was supported by only one 4x6 post, but the other side of the stairway parallels the main support beam for the house. This beam is currently supported by two adjustable posts on top of screw jacks, spaced about 8' apart, and is not sagging, but the 6x6 post in the center is no longer being used to support it.

There are no other footings for the other posts in the basement, but they are not based in concrete nor are their floors sagging. They also don't span such a large area. It should be an interesting conversation with the engineer and I think I'm going to gain some good experience with footings in 2013.


nealtw 12-10-2012 10:03 PM

Some times the footing are put in below the floor and some times people just dig out a trench before pouring the floor. So rent a hammer drill with a 1/2" bit about 12" long and drill some holes near where you want to put the posts. If you find concrete 8 to 10 inches thick you may get away with it. If it is thick you may want the drill to be handy when the engineer is there, with a few holes you could see how big the footing is.

BridgeMan 12-12-2012 09:15 PM

And keep in mind that making Swiss cheese out of the floor with your hammer drill, as nealtw suggests, may render it useless for supporting any significant column loads. A good testing lab man with the proper ultrasonic machine can determine the floor thickness without drilling a single hole.

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