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Shoring up a sagging floor

MichaelW | Posted in General Discussion on March 31, 2007 05:46am

I have a 1924 bungalow. Over time, the 2 by 8 floor joists have sagged and my floors are not level. The problem is particularly bad in the back hallway. None of the doors in that hallway close because the door frames are not square anymore. And since there is a wall there, as it has sunk the floor on the third story has sunk as well.

So here’s my question. Can I shore the floor joists up from the basement? Can I buy some adjustable floor jacks and raise the floor from below? I don’t think it would take much raising–it hasn’t sunk that much.

If I can do this, how slowly should I raise it? Will this cause cracking or other problems?

Thank you!

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  1. DanH | Mar 31, 2007 06:31am | #1

    Yeah, you can do it. The rate of jacking doesn't need to be excessively slow -- over a period of days but not necessarily weeks. There may be some cracking of plaster but less than you'd expect.

    It is important to take some precautions. The jacks need to be on some sort of load-spreading pad (the basement floor in those old houses is usually pretty thin), and the top of the jack needs to be well-secured to whatever beam you're jacking.

    Plan ahead. If you're going to jack with one post and then install a different permanent post, be sure the jack post is slightly to the side of where the permanent one will go, eg.

    So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
  2. AllTrade | Mar 31, 2007 06:58am | #2

    Can you post some pics of the basement? Would help out a lot.

    Does not sound like the work of only 2x8 sag but foundation or footing problems also.

  3. Ragnar17 | Mar 31, 2007 10:28am | #3

    I agree with Alltrade -- there's probably more at work here than just the floor joists.

    You specifically mentioned the back hall being bad.  Given the typical floor plan of 1920s bungalows, I'd assume this back hall is nearly directly over the house centerline, where you probably have a main beam (6x6 or something like that) supporting the floor joists.

    Is it possible to visually inspect the main floor framing?  If you can get a look at the main beam, I suspect you'll find it's either sagged at midspan, or that one or more of the posts has sunken over time.

    Either way, this is not a difficult fix either, so don't be alarmed.

    Let us know what you find out.

  4. Piffin | Mar 31, 2007 01:38pm | #4

    Yes, it is fairly easy to jack things straight as far as floor goes, but from what little I can see of this so far, it sounds to me like more is going on. If I hear yuou right, there is a wall transferring loads al the way from upper floors down and deflecting the floor. That souns like a location where they should have had ehad extra framing to pick up that load. For instance, if this wall sits on flooring between two joists parralleling it and it catches load from above, you have a much more serious problem. Jacking up those joists from below will likely only create more sag in the floor between joists and not moove the wall up. So you do need somebody knowledgeable on site to analize this for you, or a barrle ful of photos to post here for advise and arguementation.

     

     

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    1. User avater
      McDesign | Mar 31, 2007 02:47pm | #5

      <post here for advise and arguementation.>

      Just what I enjoy most about this place.

      Forrest

      1. Piffin | Mar 31, 2007 04:22pm | #6

        you are on the rwrong track then when you keep bragging about the wife and kids. There is nothing to argue there! You have plenty to be bragging about.;)but seriously, certain arguements here are where we learn more from each other 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. User avater
          Sphere | Mar 31, 2007 06:39pm | #7

          "certain arguements here are where we learn more from each other"

           

          Nu-unh, it isn't.  (G)Parolee # 40835

    2. MichaelW | Mar 31, 2007 07:47pm | #9

      Thanks for your help and questions.There are two 6 by 10 inch beams that run parallel, east/west under the main floor. The floor joists sit on these beams, running north/south from the foundation wall to the first beam, then from the first beam to the second, then from the second beam to the foundation wall. It is the floor joists on either side of the first beam that I am concerned with. The hallway walls run north/south, so they run on top of these floor joists and perpendicular to the beams. The floor joists drop about 1/2" over 48" on either side of the first beam. The beam is in there a little cockeyed--rotated slightly so its sides are not perfectly perpendicular to the ground. It also has a small crack in it. So I suppose it is possible it has raised up a little, contributing to the problem.I've attached some photos of the first beam.Thanks again for your advice.

      1. Piffin | Mar 31, 2007 07:54pm | #11

        Those photos need to be in JPEG format 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. FDC | Mar 31, 2007 10:51pm | #12

          From the photos the post and beams look good, the small cracks arent anything to alarmed about.  Whats the span of the 2x8 joists?  Seems like the concentrated loads coming down are not properly carried by the joists,( maybe falling to far off center). The beams all look good, original like, but sometimes without some foundation or post pad failure, like sinking, alot of floor saging in one area or around some door headers could have been either the load transfers down were  not made continuous originally, or some butchery type of remodelling was done at some time, (taking out a bearing wall or installing a header  and not suppoting the header supports themselves with positive blocking under the ends and all the way down. 

          1/2 in is quite a bit of deflection in 4 feet,  should have been 2/10-12s originally

          I dont think lifting the beams you have or and shiming wiill help, and I dont think you want to add additional  beam under center of joists?  Maybe bolstering your floor joists, by what method?,  doubling joists, or checking load path down and adding some type of built up beam in the joist space directly under point  loads. Once alot of deflection has occured it really hard to get some thing else , like a doubler inside the joist space, not to mention wires, plumbing ect , by the time you trim a 2/8 to fit in, not a lot of load carrying ability left there.   My honest opinon would be to consult with a experienced and good remodeling contractor so you dont end up butchering your  house   with some hacked up add on repair.   

          Its funny because in certain era houses like turn of century the center line beam would be undersized, sagging and the joists ok

          Edited 3/31/2007 3:52 pm ET by FDC

      2. AllTrade | Apr 01, 2007 12:33am | #13

        FDC makes has some good ideas to start.

        By checking the load path upward you may find your problem.

        I believe there is a load transferred  to the area sagging from above.

        Most likely on one or both of the walls in the hall.

        While you do have about a 3/4" deflection in the main beam I believe there is too much load on one or more of the floor joists you mention. If this ends up being the case without the load total we cant make too many suggestions but a fix might be adding steel under the load  next to an existing 2x8 or even adding a steel plate and bolting it to the 2x8 but it all depends on how much load we are talking about.

        1. MichaelW | Apr 01, 2007 01:03am | #14

          Here are the photos withe the JPG extension. The previous versions were JPEGs, but without the file extension the computer doesn't know which program to use to open them.

          1. Piffin | Apr 01, 2007 07:50am | #16

            Those first came across as applications rather than files, according to mine.That is one clean space!!!But I can't see anything wrong from what is there. previous posteers covered a lot. You probably need on site help to ID what the load path is that is causing the stress and sagging. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

  5. grpphoto | Mar 31, 2007 07:33pm | #8

    In addition to the jacks, you want to look into stiffening up the floor with solid wood blocking. The practice back then was to put blocking in with 1x4s run from the top of one joist to the bottom of its neighbor. Replacing these with solid 2x8s will help a lot. If one of two neighboring joists has sagged more than the other, jack it to the same level before installing the blocking.

    If you have pipes or wiring between two joists, Use two 2x4s for the blocking. Make sure all of the blocking is in a line; don't stagger them to make it easier to nail.

    George Patterson, Patterson Handyman Service

    1. Piffin | Mar 31, 2007 07:51pm | #10

      "The practice back then was to put blocking in with 1x4s run from the top of one joist to the bottom of its neighbor."That was called bridging, not blocking 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

  6. IdahoDon | Apr 01, 2007 06:52am | #15

    I’d use a water level first to determine what is high and what is low.  Without that I’d feel silly suggesting where to raise anything.

     

    Once a baseline is determined then follow the load paths upward to find what else is out of whack.

     

    New post supports need properly sized footers and can't simply be plopped down on the slab.

     

    Overall this is the type of structural question that is close to belonging in the, "if you have to ask don't do it," category since the number of issues it brings up affect the entire structure of the house and have to be looked at as a whole.

     

     

     

    Beer was created so carpenters wouldn't rule the world.

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