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Floor Jacks Under basement Floor Joist... cracked plaster

Floor Jacks Under basement Floor Joist... cracked plaster

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  #1  
Old 09-27-12, 12:51 PM
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Floor Jacks Under basement Floor Joist... cracked plaster

OK, so here's my question to anyone out there who may be reading and may know the answer.

I had a badly settling floor on the second floor of my wood frame house and floor jacks under a center joist in the basement, the bottoms of which were crumbling with rust. I replaced the rusted jacks with new ones set on solid, cinder blocks. Using a level, I attempted to lift the joist a bit. I've since discovered I should have cranked the posts out no more than about a quarter of an inch. In truth, I have no real idea how far I cranked them up. I cranked them out till they were very, very snug. It seemed to make no real difference in the level of the joist or the second story floor and, as you might expect, some of the plaster and lath walls have cracked. No other damage seems to have occurred. I am in the process of repairing the walls and replacing some of the cracked plaster with drywall. My question is this, before I affect the repairs, should I retract the floors jacks or just let it alone, since the damage is done. I installed the floor jacks over six months ago. Should I expect any addition cracked walls, at this point?

Thank you!
 
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Old 09-27-12, 01:57 PM
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Some terminology questions - What are you describing as settling? Are the floors dipping or way or are they out of level all in the same direction? Are you jacking against a beam (usually built up dimensional lumber like three 2X12's) or are you jacking against an individual joist - typically a single 2X? piece of lumber. Based on the rusted jacks, the problem isn't new.

I'm assuming you are jacking against a beam. What do you mean by not level? Is it sagging? If so, how much? You can figure that out by using a taut string and a line level. I would not do any permanent crack repairs until the structural problem is fixed.

Can you describe how the second floor is supported? Typically load bearing interior walls support the span of the second story joists and transfer their load to the main carrying beam for the house.

BTW - When you are done I suggest replacing the jacks with lally posts. Jacks are not acceptable as permanent support - at least not in my area.
 
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Old 09-27-12, 07:02 PM
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Hopefully the terminology was incorrect on the "floor jack" thingy, too. Surely no one would use hydraulic floor jacks to hold up a house........EXCEPT for the 5 I took out from under an addition a couple of years back Footings were poured, but no blocks, just hydraulic bottle jacks.
 
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Old 09-27-12, 10:10 PM
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Floor Jacks Under basement Floor Joist... cracked plaster.

Sorry for my lack of correct terminology here. What I'm calling a joist is the main carrying beam, 2 or 3 2X12s. The "jacks" are posts with threaded tops for expansion and the second story floor in question is high on the sides and slopes downward toward the middle, such that an office chair with casters wants to roll to the middle of the room. The room in question is the only one with an obvious problem (there are two others and a full bathroom also). It is anchored to two exterior walls and two interior. All the rooms have hardwood floors except the bathroom, which has a floating, laminant floor, so I believe another sloping floor would be obvious. All the floors creak a little, but seem structurally sound, otherwise. The posts I replaced, that were rusting out on the bottom, sat directly on the concrete, basement floor, which was prone to flooding when we first moved in. They also were expanded by cranking out a threaded screw on top. I hope this clarifies the situation. Thank you both, gentlemen, for your interest and any advice.
 
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Old 09-28-12, 05:30 AM
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I would wait until I got the flooring fairly level before I did any crack fixing, as you will surely have more as the floor is raised to level. How much more do you think you need to lift the beam to achieve this? What is the unsupported span across the ceiling of the main room where the sagging is? I am assuming, too, that the basement is considered "sublevel", and you have a floor above that, and the affected floor is above that one. Have there been any walls removed for additional space requirements, like a dining room or kitchen area, that you know of?
 
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Old 09-28-12, 06:31 AM
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Thanks for the clarification. The jacks are most often called house jacks.

Depending on the length of the carrying beam I would space 2 or 3 jacks near the low point and raise them incrementally until the carrying beam is straight. The first thing to do is to determine how much you have to move it. Once you get that figured out just raise the jacks a bit every day until the beam is straight. The jacks will be much more than snug.They will be supporting considerable weight. Are you jacking in a basement (against a slab) or in a crawl space? The jack will need support on the bottom. Basement slabs are usually poured with a footer designed to carry the load of the beam supports. Is there any indication where the original supports were located?

You should also take a close look at the beam itself. If there is any indication that it's failing it should be replaced.

Lally columns are a steel pipe filled with concrete. They are designed to be cut to suit and will provide permanent support for the beam.
 
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Old 09-28-12, 07:42 AM
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Floor Jacks Under basement Floor Joist... cracked plaster Read more: http://www

Hello again,

The basement is not a crawl space... it's a full basement with a full concrete slab floor. The beam seems in really good shape. As the weight of the second story floor transfers down, the beam supports only one wall of that room. I do not believe the first floor has been modified, i.e. walls removed, load-bearing or otherwise. The affected room is approximately 10 X 13. I needed to replace the Lally column because it was rusting to pieces on the bottom and, as far as I could tell, was doing very little to support the upper floors (it came out pretty easily). Originally, the beam had two Lally posts spaced equal distance across it's length, one remains in place and seems sound. I replaced the rust-out Lally with two posts, spaced equal distance across that remaining part of the span. I positioned both replacement posts before removing the one Lally post.

Tightening the crank on the post until it was very snug, may not be the most accurate description of the install. I extended the handle of wrench by placing a 3' pipe over it, to increase leverage, and cranked out the threaded screws on the tops of the posts until I felt they were supporting the full weight of the beam. I could have continued cranking however. Tightening the posts seemed to have no real impacted on a level placed under the bottom of the beam during the tighten process. Once it became apparent that the level of the beam was not changing, I stopped cranking out the post, once I felt the beam was supported.

I'm don't honestly know if anything I did affected the sloping, second story floor. Nothing seemed to change upstairs.

Ideas... suggestions?

Thanks again, folks!
 
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Old 09-28-12, 10:05 AM
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Terminology again? With a sagging beam/floor you should be shooting for straight, not level.
 
  #9  
Old 09-28-12, 10:50 AM
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Ideas... suggestions?
Sure.

First of all, as Chandler said earlier,
Originally Posted by chandler
I would wait until I got the flooring fairly level before I did any crack fixing
In fact, I would remove the plaster and drywall on both sides of the load-bearing wall that's on the first floor above the beam - at least any and all drywall and plaster that appears to have been installed after the beam sagged and the wall finish cracked. As you discovered the hard way, the first reaction of many homeowners is to just patch the wall, which does not cure the problem. If you do the same, that won't cure anything either. You will surely get more cracking in the future.

Inspect the bottom of the beam for evidence of missing support piers. Inspect the basement floor for any evidence of footers, especially below any support "ghosts" you found on the beam. Consult with - hire - a structural engineer to tell you how much support you need, and where.

To raise and straighten the beam, you will need a set of house jacks - not the "hydraulic bottle jacks" that Chandler mentioned earlier, but very strong screw jacks - set so that the places where you need to install the permanent supports remain clear. Those jacks are short and sturdy, so they will need to sit on "cribbing," which is a tower, or pyramid, made of short, cured pieces of heavy hardwood timbers - 6x6s at least, at the floor, and 4x4s at the top. Leave enough space to place one 8x8x3' timber and a heavy steel plate (should come with the jack) above each jack. Snug each jack up enough to keep everything in place.

The lift is made by raising each jack about 1/8" or so, once a week. The week-long wait between the times you raise the jacks gives the framing time to adjust back into place. Your house didn't have this sag when it was new, and it didn't occur overnight, or even over a few weeks or months.

If this sounds like more than you're prepared to tackle by yourself, you can get the report from the structural engineer and hire a house moving company to do the work. The only thing is, those folks are generally reluctant to undertake a job that will require them to send someone to the site once a week over 2 or 3 months, and it can be expensive when they do. Maybe some have adapted, if there are a lot of old housed with structural problems where you are. Or, maybe, you can negotiate with them to let you do some of the work yourself.
 

Last edited by Nashkat1; 09-28-12 at 10:45 PM. Reason: correct nomenclature and information.
  #10  
Old 09-28-12, 05:54 PM
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Floor Jacks Under basement Floor Joist... cracked plaster

Thanks guys!

This sounds like it's going to be a long process, over time. Thanks for all your time and info on my behalf. I'm much better informed now than when I started. I'll have to start with checking local codes and researching companies that can do the work. I'll try to update the forum as the repairs evolve. This is a great forum and I really appreciate your personal interest! You've been terrific!
 
 

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