I realize that this question is probably the least DIY-type of question one could imagine, certainly for an amateur.

I'm for now simply curious about what options exist. This is an old wooden house, which is sagging some in the middle on all floors.

The cheap way to fix this appears to be simply putting down new flooring to straighten the floor without fixing the root cause.

However, is it possible to correct the root cause, as in straighten the whole house itself?

What is such a procedure called, and what heavy tools and machinery (if any) does it involve? What skills are required?

It would be useful to at least have read a little bit about this when discussing options with builders.

  • can you share a picture? Is it a single story home or multi?
    – depperm
    Feb 28, 2020 at 12:48
  • Multi, two floors plus a basement and attic. I don't have a picture at hand, unfortunately. Feb 28, 2020 at 12:49
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    This cannot be answered without a whole lot more information. There are many ways that buildings and their foundations are constructed and the actual situation with your house will play into what is required.
    – Michael Karas
    Feb 28, 2020 at 12:49
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    In an older wooden house, very likely it is structural - that was extremely common, anyway.
    – Ecnerwal
    Feb 28, 2020 at 14:33
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    Sounds like subsidence in the underlying ground to me - Chimneys are heavy and will sink into the ground over time, even if the ground was properly prepared. This is not a home-gamer problem, you need expertise to fix it, which means inspecting it. Is a problem too-big for remote-advice to give precise advise.
    – Criggie
    Feb 28, 2020 at 22:15

4 Answers 4


The process is simple, but actually doing these things may take equipment and expertise that you lack.

  1. Find out WHY the floors are sagging. Is it due to improper foundation/footings? Is it due to failed or failing materials? Is the structure just inadequately design to support itself?

  2. Come up with a remediation plan to fix the issue(s) you identified.

  3. Do those things yourself or hire a contractor with the necessary expertise to take care of them for you.

I'll add that in my experience the most common problem causing floors to sag in an older home is subsidence in the support structure either because they are inadequate or have been undermined. Usually the process involves jacking up the sagging parts, usually using foundation jacks. This often needs to take a while because you want to avoid breaking any joists, walls, etc. Then you shore up (if possible) or remove and replace the failing/failed supports. After that you let the building down on the new supports.

You will almost certainly end up with plaster cracks and the like but simply putting down new flooring without fixing the root cause is just a waste of time and money.

  • Yes, jacking a sagging understructure is a process that should be done over months a little at a time. Impatience can break the house.
    – Ecnerwal
    Feb 28, 2020 at 14:18
  • Had a sagging floor, took the boards up, sorted the supports for the joists and put the boards back. Good one, but mine was easy...
    – Solar Mike
    Feb 28, 2020 at 17:21
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    Note too if a house is pretty bad there was probably years of work done that altered different things because of the sagging. And once it is straightened, those things will have to be altered back.
    – DMoore
    Feb 28, 2020 at 22:35
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    Agree that slower is better than faster when jacking up a house. But around here they do that quite a bit in order raise the house above the updated flood zone levels. And it never takes several months to get the house raised to the new level.
    – SteveSh
    Feb 28, 2020 at 23:09

In the extreme case, start again!

An old (Tudor-era) wooden house near me was in a bad state of disrepair for a number of years, and then they had a fire. Being a historic building, they were not allowed to completely demolish it. So the upper floor was kept intact, and the entire ground floor structure was removed, leaving the upper floor structure only connected to the ground by the brick chimney and a lot of props.

Removal of the ground floor in progress. I did take some pictures at the time, but sadly I don't have easy access to them at the moment. Trust me, it's an unnerving sight to have a house with an entire intact upper floor, and absolutely no walls holding it up!

  • A lot depends on what the land is worth. It's pretty common where I live to demolish a 50's or 60's era waterfront house down to the foundation and build a McMansion on the existing footprint.
    – SteveSh
    Feb 28, 2020 at 23:12
  • Less common in the UK, but then we build almost exclusively with brick. Most timber framed houses over here are likely older than the USA! And as such, there are strict rules on what you can and can't do with them. (They're called "listed buildings", because they literally go on a list of historical buildings.) The more significantly historical, the stricter the rules.
    – Graham
    Feb 29, 2020 at 0:05

This is a pretty vague question, but based on the info, it sounds like just the floors are sagging. I imagine that based on that, the walls may also be leaning inward. That would indicate that this is what is referred to as a “balloon house.” That means that the floor joists are tied to the wall studs. So when the floor joists start to sag, the wall studs are pulled in toward the house. This would be mostly seen in the second story of a two story house. Outside of that, if you’re referring to just a sagging floor, then it sounds like you may have a lack of support over a certain distance of framing. Over time, the floor joists sag, and there’s little you can do if the sag is more the two or three inches over the longest span if the floor. If the sag is minimal, you can use railroad jacks to straighten the floor. Place the jack about midway the span of the floor joist at the first joist that shows sag. Raise the joist level with the rest if the joists if possible. Raise the next joist in the same manner. If this causes warp instead, raise the joist one third the distance instead.
If you don’t see results from either of these methods, and you likely won’t, here is the next most effective method. Pull the joists and flip them upside down.

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If there's a problem with the house's support structure, it's possible (and probably even recommended, for the long-term good of the house) to fix it, but beware that you can't perform major surgery on a house without a few consequences.

I bought a two-story house in 2015 that was built around 1930, and had some very pronounced humps on the first floor. Inspection in the basement showed that the main beam holding up the first floor wasn't sitting squarely on its support columns, and was slowly "rolling" off of the columns, making everything uneven.

I had a contractor come and straighten things out, which involved building temporary load-bearing walls in the basement to support the floor above, removing the columns, cutting out the main beam, replacing it with a new laminated lumber beam, setting new lally columns in the concrete floor, re-hanging all of the floor joists from the new beam, and then removing the temporary walls. This took a few weeks, and in the process everything was made laser straight and structurally sound.


  • What had been slowly settling for years was jacked up straight over the course of a few days. Up above, drywall, paint, and grout all cracked in places. The kitchen had been remodeled by the previous owners just a few years before (and therefore had been "built straight" on top of a very crooked floor, exactly what you're describing in your question), with the result that tiles popped and cracked, a marble counter broke, and cabinets and drawers were put out of alignment. Fixing this was expensive.
  • Every pipe, conduit, and cable in the basement that had crossed from one side of the beam to the other had to be cut down before the work was done and put back together afterwards. In my case that meant that the house was without heat (not a problem, as the work was done in summer) and partly without electricity for the duration of the work.
  • The first floor of this house had no subfloor. A hardwood floor was nailed directly to the joists. For most of the length of the house, a wall sits above the main beam, but the living room crosses the beam. At that point, the floor was nailed directly to the beam. When the beam came out, so did a one-foot-wide section of the floor! I ended up having a new floor put in across the entire first floor, again, at some expense.

I wasn't warned about any of this, and it didn't occur to me on my own, so if you're pondering something similar, make sure to keep asking questions!

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