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How do I *really* level a subfloor?

rickchem | Posted in General Discussion on May 23, 2002 04:40am

Hello all-

   I once read and posted on here often, just returning after a few years.   I have a subfloor where it appears, on adjacent joists, one bowed up while the other bowed down (one was crown up, other crown down?).  Compounding this is the edge of a fridge and dishwasher on opposite sides of the kitchen rest on the joist bowed down.  The resulting swale is visible, and is maybe a 1/3 of an inch + or – from level depending on which joist.  The floor feels solid.  I’d like to correct it!  I’ve done little structural work other than new construction a ways back.  The homeowner tells me when the house was built (22+ years), the subfloor or underlayment (they are unsure) was replaced in that area as the Solarian floor cracked after installation (and there is a crack there now).

   My solution is to get my heavy friends to stand on the up joist while I sister another to it, and then jack up the down joist and then sister one to it.  Would I need a full joist to do this, or could I sister a 2X4 or 6 to the lower portion?  Any other ideas???  I’d like to have a sturdy floor for tile! 🙂

Thanks. . .

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  1. User avater
    JDRHI | May 23, 2002 05:44am | #1

    You will never get the bowed boards to hold the point to which you either jack or bend them to.

    If the framing is indeed sound you can sister to the joists as they are. If floor height is not an issue string lines from your high point level around the room and sister all the joists to this height. If height concerns you, try planing down the "one" high joist to the level you desire and sister remaing joists level. I recomend sistering all joists as it is doubtful only two are no longer level. Use nothing smaller than 2 x 6 to sister with and gang nail the heck outta them. Be sure to reattach any strap bridging you cut out when sistering.

    Good Luck!

    J. D. Reynolds

    Home Improvements

    "DO IT RIGHT, DO IT ONCE"



    Edited 5/22/2002 10:45:26 PM ET by JAYBIRD

  2. Schelling | May 24, 2002 01:11pm | #2

    You will need sisters of the same depth and as long as you can get in the space though they need not necessarily be the full length.  Cut most of the way through the offending joists starting from the top. Drill a hole at the top of the joist and cut down with a sawsall until you are two inches from the bottom. If the joist is low, jack up and nail on the sister. If the joist is high, add weight above until level and then nail on the sister. In the case of a high joist you may need to cut more kerfs or even all the way through the joist to get the floor to drop. It may be necessary to wait days or weeks for the unsupported floor to drop. Good luck.

  3. Manzier | May 24, 2002 11:03pm | #3

    Question:  How do you ask your "heavy" friends for that kind of favor? 

                                       

                                    :) O =

    1. User avater
      JDRHI | May 25, 2002 06:16am | #4

      Just call em over for pizza and set up the table where necessary. J. D. Reynolds

      Home Improvements

      "DO IT RIGHT, DO IT ONCE"

      1. AlanSenoj | May 25, 2002 08:46am | #5

        Shell's got it right, but why would you cut from the top? A high crown will never come down.

        With a high crowned joist, you must cut from the bottom.

        One sister will do, I usually glue and nail. In tough restricted access areas, sometimes a couple of narrower boards, say 2X6's, one on each side of a 2X10, will do the job.

        Yep, big friends, a little salsa music, don't worry, be happy.Alan Jones

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