House beam in basement

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fredcapo

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Hello. I recently purchased a circa 1915 house in northern NJ. The house shows no signs of settling...straight ridge lines, minor hairline plaster cracks, level and plumb walls, no bouncing floors, no foundation cracks.

The house has a 21 foot center beam in the basement that is holding up the floor joists. It is made of 2 sistered actual measure 2 x 8 beams, apparently tied into foundation/sill and supported by 2 tree trunks appx 7 inch diameter. The concrete floor has a few weep holes which have been dry during the 7 months I have owned the house. Using a feeler gauge, the concrete appears to be 9 inch thick. What we have is 1/2 to 3/4 inch sag between the tree post spans.

Need to mention we removed a lot of weight from the floor including radiators and stonework...probably a ton.

I realize the 2x8's are undersized by today's standards, though they have yielded to the sag...

I would like to straighten or minimize the sag, and reinforce the situation. I would prefer to not replace the horiz beams or dig up the basement floor. Is there a prudent way to do this? Thanks.
 
Without putting a proper footing under the slab anything you do will probably not work well to shore the beam and level the floor.You can take the trees out and replace with lally columns adding one in the center and jack the beam up a bit.Can't hurt anything .with a 9" slab you may or may not be ok.It will do you no good to reinforce the beam if there is nothing under the slab to support the columns.
 
Welcome to the site.
Hand mixed concrete was often sad so I would suspect that new was poured over bad. If it is 9" thick it might be fine but if you could prove it. Any chance of just building a wall under the beam, that would spread the load and have a better chance of success.
 
Sorry for the unreadable post.The forum keeps hanging up on me in the middle and can't be fixed without errors.
 
Thanks for response. I like the idea of building the wall since I would like to partition the basement. I would like to use a combination of frame construction and monopole adjustable. Is there a legitimate way to integrate the jak posts with a frame wall? Would adding additional similar sized sister beams be helpful?
I would like to eliminate the tree trunks.
 
Let's talk about the floor first. I would start by drilling a few holes near the spots where you would like to put new posts and prove the thickness is there.
 
unlikely that I will locate an ultrasonic thickness measuring gauge to borrow so will buy a suitable bit.

Just thinking ahead...Considering that the two original trunk columns have apparently not sunk in 100 years, have to expect there is a footing at least in those two locations. If then create a 4 2x8 beam, two posts may come close to being sufficient with some additional framing...
 
That is a reasonable arguement but it would be your call .
The fix would be the same whether put in footing or not. You need to build temperary walls on both sides of the beam. With a plate nailed to the floor joists and on one the floor. Cut studs just longer than would be need to reach. Push them in on an angle and nail one under each joist. Then tap the bottoms in to place and level the floor. With a little planning a simple math you could have it level when the studs are straight. If the lift is to much for that to work easily, you take it up half way and then place another longer stud beside those and lift some more.
Get all this figure out and planned and then worry about what to do with beams.
 
Thanks. I was thinking about using a set of product such as the Ellis steel shore, which is a monopole one piece jack rated at 8000 lbs, to do the lifting and holding, to enable installing the fixed posts and then adding framing and maybe using the shores as extra support. I just don't know if the 8000 lb rating of each shore is sufficient even for the temporary lift (though looking at it simplisticly, I don't know of any 8000 pound direct loads in the house...) thanks.
 
Leaves alot of questions, If the joists land on the old beam you need to support both sides. If your lifting the old beam how do you level the floor joist for the floor above.
 
Neal, thanks for your ongoing interest and valuable advice, but I don't understand your post... If I am jacking up the beam, it is lifting the (sagging) floor joists...To enable me to install new and additional support to the beam. At some appropriate time (dont know yet) in the process I will sister the beam...
 
Like I said more questions.
The concrete is supporting the posts that are there, there may be footing below that or the concrete is thick enough every where, we don't know.
So we don't know if you can put a jack a few inches away and find concrete that will do the job.
If ytou go ahead and jack up the beam near the old posts, what do you expect the beam to do? Over time there is a good chance it can be puched back up to straight (reasonably straight) 1/8 to 1/4 inch per day or you could break the beam. And that dosn't count for any sag that is between the posts.
What I suggested would spread the load on two temp walls over the full length so the concrete has a better chance to support it. As the joist are lifted to level. the post will be free to move and the beams may fight your action or the nails could holding them to the beam could just pull out or may need to be pulled or cut.
Once you have the floor level, new post could be placed in the same location as the old one and new 2x10s could be added to each side of the beam between each post to compensated for the sag between posts.
 
Neal, thanks. Yes as said earlier I like the idea of building the wall under the entire beam. I understand the concern about the slab and i will have to make a measurement somehow.

For the bearing wall am thinking that I will use 6 inch lumber either 6x6 or 2x6s supporting the beam comprised of the two original 2x8 plus 2 additional sistered 2x8. Not sure what would be the best floor plate.

But I need to raise the sag. Where the tree stumps are the beam appear to be at the correct height. I thought using the metal mono post jacks to temporarily raise the sag was the way to go..
So you are saying from what you only can judge from a distance, do not jack but attempt to raise the 1/2 inch sag by inserting the longer vertical wall studs, in-situ, where they will stay, on the plate by tapping them in.

I fully understand your need to present a cautious suggestion.
 
The walls I was talking about are just temperary to lift everthing level, then you could just add to the beam but I would go up to a 2x10 on each side of it, where you want to build a wall you can just remove the beam and build a new wall in it's place. For that I would go with 2x6 studs 16" on center and two 2x6 top plates and a 2x6 bottom plate.
I would lift everything up level and happy, remove the old posts and section of beam where wall will be replacing it install new posts. One of the posts can be just 4 studs built into the end of the new wall add a 5 1/2 x 5 1/2 post, that should be set in a saddle in the floor,that hold it in place. Then you can build the new wall with plastic sheeting between wall and concrete. Then nail 2x10 to each side of the beam, snug up to the floor joists, 3 or 4 nails ever 12 to 16 inches.
Then remove the temp walls
 
Neal, thanks. I needed the additional explanation. I understand and believe what you have presented is a good approach that will yield a permanent solution.
 
Neal, I plan to start in a week or so. Seems like 99% of folks are removing bearing walls and I am doing opposite, but the wall will work well to partition the basement.

My thought is to leave the original beam (2 2x8) for most of the length and build the permanent wall directly under it, only perhaps making a single 36" pass through.
 
Your beam will still have humps and bumps in it and will take some time to straighten out. But if you do that you don't need temp walls just use the same proceedure to build the wall under the beam.
Just take up a little each day to give the wood time to change, old dry wood is set in it's ways and dosn't like to change.
 

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