"correcting" deflection in 100-yr old floors and walls 2

[SLTA]

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?

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[dicksewerrat]

Can you post a drawing of this bldg.?

Richard A. Cornelius, P.E.

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[jayrod12]

Without removing the existing hardwoods there's no way to "fake" levelling the floors.

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.

 

[SLTA]

jayrod, explain a bit more about shimming between the offset walls?

sketch is attached, with rough settling patterns of floors shown in red.

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[jayrod12]

Those are ugly offsets.

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.

 

[SlideRuleEra]

SLTA - Take a look at the defection curves in sketch. Looks like max deflection is where the interior walls are bearing on the floor. You did not mention the size or spacing of the floor joists, are they overloaded in bending? Perhaps some, or all of the deflection is for this reason rather than differential settlement of the joist supporting walls.

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[SLTA]

The joists are seriously beefy, like 2x12 @ 16" oc., old-wood. They all seem to be fine. No cracking, splitting, etc, other than one joist where a plumber had at it, but it's already been repaired appropriately.

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[msquared48]

The old joists will not, and I said will not, take well to any leveling.

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)

 

[jayrod12]

2x12 Joists are beefy, but not when they have to transfer the load 2 feet one direction and then 4 feet back the other. Have you take actual elevation shots to confirm your sketched deflected shape is actually what is happening on site?

 

[Brad805]

Do you have an estimate of the amount of deflection? The typical sketch suggests this has less to do with age, and more to do with a misunderstanding of load transfer. It seems some beams are in order, but it will be great fun to figure that out given none of the members are likely to have a grade stamp.

 

[precast78]

I think adding dropped beams at each level is your best bet starting from the bottom. You jack up the beam first to level, then add the columns. If there is not existing foundation then you have to pour a new one.

 

[JAE]

Just keep in mind that the joists are probably permanently deformed in that deflected shape.
Any jacking will need to be designed to take that into account.

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[dhengr]

SLTA:
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.

 

[hokie66]

JAE is correct. You can improve the strength of the floors by reinforcement, but without removing the flooring, you can't expect to remove the curvature. If you jack them into new positions, slopes will remain, but just translated up a bit. This will likely cause further distress in the wall finishes and openings.

 

[Ron]

This is creep and plastic deformation. As others have noted, not a good condition for wood. I would sister joists to the existing and remove the deflection by jacking. You will likely damage the existing joists so don't attach the sistered joists until jacking is complete.

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.

 

[manstrom]

What about a self leveling topping?

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.

 

[dcarr82775]

If you end up going down the jacking road, remove the sheathing from partitions parallel to the joist span will help. They are going to crack to all heck anyway so might as well remove/replace the sheathing anyway and help the jacking process. I don't see jacking 100 years of creep out in a week or two either. You will definitely need to sister each joist when things are done.

 

[XR250]

I always specify that the existing joists be notched at least 50% thru in at least three places along the span prior to jacking and sistering. This allows them to jack easily to nearly straight and does not stress out the sister joists having to deal with the joist wanting to return to its creeped, deflected shape.

 

[Brad805]

If the structure is adequate I think it should be left alone. If deficient, then obviously it needs to be repaired. These owners should not be looking at an old structure if they cannot appreciate the character they bring. Removing a 100yr old wood floor should not be an option. One cannot find that wood quality anymore.

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.

 

[SLTA]

Brad, I'm with you that it should be left alone. Now at least I know I wasn't missing something about how difficult their ideas would be.

Cheers, y'all.

Please remember: we're not all guys!