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I am building a shower and my previous contractor used this double 2x4 for the top of the wall-to-wall niche. The wall does not bear any load from above, but will need to hold the weight of the tile. I was planning to use a double 2x6 at least, so was surprised he did this. The span is roughly 5 feet, and GoBoard tile backer will be used over the framing. Should I redo it?

Bathroom photo

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  • I just realized the confusion.. the space in the middle is the niche, so GoBoard will be above and below it, but below the double 2x4 will only have GoBoard on the back Oct 20, 2023 at 14:41
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    I think I'd want jack studs on the left and right to keep those 2x4's from moving down. Oct 20, 2023 at 14:49
  • I don't get it...how are the studs fastened at the top? Looks like you have some joist "tails" sticking out. Why is the ceiling here lower than over the toilet?
    – Huesmann
    Oct 21, 2023 at 12:26
  • @Huesmann, the studs go to the ceiling and support the little ceiling joist stubs. It looks like they removed a section of load bearing wall to grow the shower's size. Instead of putting the header in plane with the floor joists, they went with bearing underneath and framed the shower ceiling at the bottom-of-header elevation. At the top of studs in the blind there must be a top plate running perpendicular to the floor joists.
    – popham
    Oct 21, 2023 at 20:43
  • How will the niche be constructed? The back wall, a large flat surface, seems like it will lack support and may flex enough to crack tiles? You'll have Goboard in front (in the shower), maybe you could place a sheet of plywood, nailed thoroughly to all the studs above and below the opening, on the back side of the wall and then the drywall for the toilet over the plywood. The plywood will add strength to the questionable 2x4s and will also add strength to the middle part of the back wall of the niche.
    – jay613
    Nov 19, 2023 at 16:34

1 Answer 1

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The paneling on both sides should effectively provide diagonal struts down to your beam to hold it up.

Assuming that your the upper wall is about 5 ft square and assuming a 10 psf wall weight (the IRC sets 10 psf as an upper bound on partition weights), then the pair of 2x4s has about 3 times the necessary bending strength (assuming connections that develop the full strength). That's with standard grade SPF lumber which is almost certainly worse than whatever you're working with.

For the deflection, however, I get 0.87". And squinting at the numbers, the 10 psf doesn't seem too far off, actually. My instinct would be to require a deflection less than L/360 = 0.17". Your pair of 2x6s achieves 0.23". Your lumber is probably stiffer than standard grade SPF, so the 0.23" probably satisfies my arbitrary deflection constraint.

If you don't trust the backer board to stiffen the header, then I would sooner put a sheet of 7/16" OSB under the backer board than rework the framing. Just be sure that the outer vertical 2x4s are well fastened to the perpendicular wall.

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