"correcting" deflection in 100-yr old floors and walls
"correcting" deflection in 100-yr old floors and walls
(OP)
ok, folks.
I was asked to look at options to "repair" the sag in the floors and walls of a 100-yr old house. The house itself is rock-solid structurally, but the potential buyers don't like the sag in the floors that comes from 100 years of vertically-offset bearing walls. The non-bearing and exterior walls have also settled to match the floor sag, mostly due to some not-well-thought-out original construction. Windows have been modified to close properly, and the built-in cabinets have drawer openings that work but clearly show the sag.
Just to make it more fun, the buyer doesn't want to consider plywood shims etc, because it would mean he has to remove the original hardwood flooring. He's suggested jacking the floors, but I have troubles with that for two reasons: a) it seems to create LOTS of extra problems and b) the offset in the bearing walls would mean having shores down the middle of two rooms. Moving the bearing walls to line up vertically would also mean replacing some existing joists, as the overlap would no longer be over the existing offset wall.
And also, as a thought - does jacking slowly (like over a course of a few years) actually work? But that would mean having jacks running along the middle of their living room for years.
Any help? Any good ideas?
I was asked to look at options to "repair" the sag in the floors and walls of a 100-yr old house. The house itself is rock-solid structurally, but the potential buyers don't like the sag in the floors that comes from 100 years of vertically-offset bearing walls. The non-bearing and exterior walls have also settled to match the floor sag, mostly due to some not-well-thought-out original construction. Windows have been modified to close properly, and the built-in cabinets have drawer openings that work but clearly show the sag.
Just to make it more fun, the buyer doesn't want to consider plywood shims etc, because it would mean he has to remove the original hardwood flooring. He's suggested jacking the floors, but I have troubles with that for two reasons: a) it seems to create LOTS of extra problems and b) the offset in the bearing walls would mean having shores down the middle of two rooms. Moving the bearing walls to line up vertically would also mean replacing some existing joists, as the overlap would no longer be over the existing offset wall.
And also, as a thought - does jacking slowly (like over a course of a few years) actually work? But that would mean having jacks running along the middle of their living room for years.
Any help? Any good ideas?
Please remember: we're not all guys!






RE: "correcting" deflection in 100-yr old floors and walls
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: "correcting" deflection in 100-yr old floors and walls
Jacking a house back up can work however it causes more damage to the finishes than removing the flooring would. And doing it over a long period of time works in theory but it works better on newer lumber than 100 year old stuff.
If you did jack the floors back up you could shim between the floor framing and the offset walls so the bearing lines stay the same.
RE: "correcting" deflection in 100-yr old floors and walls
sketch is attached, with rough settling patterns of floors shown in red.
Please remember: we're not all guys!
RE: "correcting" deflection in 100-yr old floors and walls
I may have misinterpreted your comment about the offset walls. I was under the impression it was an sloped floor less than a "bent" floor. So if you were to jack the floor up it would lift off of the offset supporting wall. I figured you could just shim the gap between the wall and the floor.
However now that I've seen your sketch, that may not be a solution to your problem. The only way that jacking the floor would cure your issues was if you beefed up the floor joists once they were level. Otherwise the minute you remove the shoring/jacks they would just settle back down.
Hopefully someone else has a solution for you, my only thought is to rip the flooring off and fake the appearance of level.
RE: "correcting" deflection in 100-yr old floors and walls
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RE: "correcting" deflection in 100-yr old floors and walls
Please remember: we're not all guys!
RE: "correcting" deflection in 100-yr old floors and walls
Either add a leveling compound if the floor can take it, or sister on new shallower joists to the existing ones after removing the flooring. Install new flooring that will function as a diaphragm.
Mike McCann, PE, SE (WA)
RE: "correcting" deflection in 100-yr old floors and walls
RE: "correcting" deflection in 100-yr old floors and walls
RE: "correcting" deflection in 100-yr old floors and walls
RE: "correcting" deflection in 100-yr old floors and walls
Any jacking will need to be designed to take that into account.
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RE: "correcting" deflection in 100-yr old floors and walls
What kind of exterior wall framing exists, balloon or platform? The jsts. aren’t really lifting of the ext. walls are they? What sort of magnitudes of deflections and cambers at the max. points and what locations? I would move the new bsmt. wall to 12', they don’t really need a 6' hallway do they? I’ll bet that most of the settlement that you see on fls. 1 & 2 is do to the defection in the 1st fl. joists, where the larger offset is the doing the most/primary damage. That’s a concentrated load 4' out on a 16' span. This will be due to deflection, long term creep/settlement, an the accumulation of max. permanent loading (D.L. plus some L.L.), a duration of loading issue. What are the interior finishes, walls and ceilings? What’s loading the 2nd fl. wall other than attic jsts. and insulation? This kind of problem usually requires considerably more experimentation and engineering judgement, than exact science.
Put a beam and a couple jack posts down in the bsmt., under the wall above, and lift it .5". Listen for any cracking and snapping while you do this. Move the grand piano away from that area on the 1st fl. Inspect the interior finishes in this area for any cracking. Let it sit for a few days or a week, and repeat another .5" cycle. Monitor what this is doing to the 2nd fl. level also, to see if this isn’t pretty much correcting that problem too. Then settle for a 4' bsmt. hallway. Of course, you’ll then have to unfix all of the doors, windows and cabinets which have been adjusted to work over the years, along with a few plaster cracks. Maybe humidify the house for a few weeks before you start this, to get some moisture in that old wood.
RE: "correcting" deflection in 100-yr old floors and walls
RE: "correcting" deflection in 100-yr old floors and walls
Based on your sketch, this is not a foundation issue. The offset has inflicted creep and deflection into the floor system at both locations.
The jacking line should be under the overlying wall, not along the deflected joists, assuming the floor can withstand the jacking compression.
RE: "correcting" deflection in 100-yr old floors and walls
I did repairs on a new building with terrible deflection problems. We ended up using 1" and 2" styrofoam as a base filler (to lighten up dead load) and pouring about 3/4" of gypcrete over the top. It stiffened up the floors and added some nice sound proofing as a by product.
Yes, you would lose the original hardwoods (which seem to be all the rage thanks to HGTV). You would also need to verify the existing joists.
Adding or cutting in intermediate beams would be an ugly, difficult and possibly unsuccessful endeavor.
Jacking up wood floors in my opinion just crushes the wood. The pressure ends up being too much.
RE: "correcting" deflection in 100-yr old floors and walls
RE: "correcting" deflection in 100-yr old floors and walls
RE: "correcting" deflection in 100-yr old floors and walls
The creaking and groaning this old bldg will make when one tries to overcome the permanent set would be quite impressive. We jacked up a 50yr old train station a few years ago now that had settled 4" due to a deficient foundation. It was quite the project, but that was a easier case than this because that building merely rotated. This situation is more complicated.
RE: "correcting" deflection in 100-yr old floors and walls
Cheers, y'all.
Please remember: we're not all guys!
RE: "correcting" deflection in 100-yr old floors and walls
I didn’t mean to imply that you could remove all of the deflection and settlement in the old jsts. Certainly, there will be permanent set, you might crack a little plaster, the more so if you work to quickly. The older lumber grades, larger sized 2x12's should be adequate on those spans, except for the worst offset on the first fl. I didn’t mean it would be easy. But, I’ll bet since you are already putting in a new wall in the bsmt., if it could be put under the wall above, at 12' instead of 10', you could solve a good share of the problem. Reread my first post and resolve the questions in your own mind. If you spent a day in the bsmt. with a beam under the wall above, and a few jacks, you could get a good feel for what you might be able to accomplish. The jacks in the bsmt. for a few months might not be as objectionable as those in the Liv.Rm. I suspect that the condition on the 2nd fl. is not as serious as that on the 1st fl., and in fact the 1st fl. condition is inducing (adding to, allowing) the 2nd fl. condition. You might make the clients happy by removing two thirds of the settlement, saving the hardwood floors, and then talking about the character we like in an old house.
RE: "correcting" deflection in 100-yr old floors and walls
Although you may be able to level the floor by removing the flooring and sistering on new joists, the ceiliing finish below supported by the same joists will still read the same vertical deflection.
The buyers will be opening up a real can of worms here if they try to do this. I, too, stongly recommend against this.
Mike McCann, PE, SE (WA)
RE: "correcting" deflection in 100-yr old floors and walls
In this case the job was a gut rehab so damages to finishes were not a concern. But we wanted to preserve the stair rise and run as evenly as possible for each floor and keep as much ceiling height as possible. If you simply shim and level the floors without jacking you may have an uneven top riser in your stairs. Every building is different. If you can find a contractor experienced in doing this kind of work get him on board and pick his brain. It will help you decide if the time and cost of jacking are worth it.