I'm renovating a 4x5 ft. bathroom and I'm having problems leveling the sistered joists with the existing floor (the doorway). I've clamped the new sister joists to the old ones in order to see how it would fit. When I lay subflooring on the bathroom's joists, it is 1/4 in. higher than the existing subfloor in the doorway. How do I level it, so that it meets the existing plywood at the doorway? Is being a 1/4 in. out a lot?

Please see the pic below: I'm level east to west but not north to south. (And north to south is the critical direction as I need to tie into the existing flooring.) The joists are 2x4s on a slab. The house is 50 yrs old.

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  • If sistered joist are at the same height there are other problems. It is easy to plane off the bottom of the door if everything is level and square.
    – Ed Beal
    Commented Oct 12, 2016 at 0:25
  • Would it be possible to plane 1/4 in. off the joists? Would they be strong enough? The joists are only 2x4s. But, I've sistered them.
    – Laxmidi
    Commented Oct 18, 2016 at 1:18
  • 2x4 is not a substantial joist, with a sistered joist I would not worry about 1/4"
    – Ed Beal
    Commented Oct 18, 2016 at 1:31

2 Answers 2


It might not be possible but Why not shim the existing joist 1/4 inch and mount the new once 1/4 inch higher.

  • Thanks for the comment. My problem is that the when the bathroom floor is finished, it will be higher than the finished floor outside the doorway. SO, I need to figure out a way to lower the bathroom joists.
    – Laxmidi
    Commented Oct 18, 2016 at 1:15
  • With a sistered joist shaving of 1/4 is fine in my humble opinion
    – Ride Sun
    Commented Oct 18, 2016 at 2:31

A quarter inch difference over a span of five feet? meh. Fudge it.

It doesn't have to be level, it has to be flat.

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