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  1. #1
    Join Date
    Mar 2008

    Default Sistering floor joists to support undersized and cut joists under tub

    I recently opened up the ceiling below my bathroom and was surprised by what I found. The floor joists are 2 1/2" x 8" x 15.5' and 16" on center. This seems way too small for the span. Also, some of the joists have been cut to accommodate drain pipes. I'm going to be re-doing the bathroom, adding concrete board and tile, and I want to make sure the load, along with the load of the tub, can be properly supported. I'm contemplating sistering the existing joists with 2 x 8 x 16' joists. Will this be sufficient to handle the load? The bathtub is about 5 feet in from one wall. To complicate things, the house is balloon framed, so I will have to attach a ribbon or ledger to the 2 x 4s to support the new beams, but I'm concerned about what kind of fasteners to use (the sheer strength of the fasteners). Any info would be great.


  2. #2
    Join Date
    Dec 2010
    Houston Texas

    Default Re: Sistering floor joists to support undersized and cut joists under tub

    For all your questions (and specifically this one) head on over to the John Bridge Tile Forum. There you can use the handy dandy deflecto-lator to see if your joists are up to speed for tiling, and if not what to do. You can post pictures and get answers specific to your house. There is also an extensive library to find answers to things you didn't know about.

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