×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

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

"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?

Please remember: we're not all guys!

RE: "correcting" deflection in 100-yr old floors and walls

Can you post a drawing of this bldg.?

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: "correcting" deflection in 100-yr old floors and walls

(OP)
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.

Please remember: we're not all guys!

RE: "correcting" deflection in 100-yr old floors and walls

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)


RE: "correcting" deflection in 100-yr old floors and walls

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?

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

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.

RE: "correcting" deflection in 100-yr old floors and walls

(OP)
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!

RE: "correcting" deflection in 100-yr old floors and walls

SLTA:
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

Another thought here...

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

Jacking can work, but doing it slowly is key, and as others have noted you will need to stiffen the jacked floors so that they do not simply return to pre-jacked shape after removing shores. You can monitor the force in your jacks with pressure gauges (I have used hydraulic jacks with such gauges). In a 110 + year old 4 story townhouse I jacked, we removed about 2 1/2" of deflection in every floor over the course of about two months. Each increment of jacking was from 1/4 to 3/8", applied over a few minutes, about once a week. We took gauge readings before and after each increment. We subtracted out the estimated dead load of the floors we were lifting from the gauge readings, and were able to have a feel for how much the deflected floors resisted the jacking. The small increments mentioned above were found necessary to limit the forces in the jacks and floor beams. It was very interesting to find that the gauges showed that the wood floor beams initially resisted the change in shape but then would gradually relax over the following days. (We did not wait for total relaxation, so its unclear if that is achievable.)

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources