I bought a 10x20 wood lofted shed. One loft is just 4 feet wide and the other is 8 feet.

I’m wanting to use the 8’ loft for totes and other storage but it’s already starting to bow underneath it a bit. Now I wish I’d ordered it with the 2x6s instead of the 2x4s but didn’t think about it then.

I was thinking of maybe a couple 2x4s propping the bottom up 4’ from the back but didn’t know if that’s best or would be enough.

Any suggestions are welcome.

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  • 1
    "Bowing a bit" isn't a problem. How's your head clearance below? Any reason you can't add taller joists to the outer joist and two back (near the center of the loft's depth) to add stiffness? I wouldn't want anything hanging below, getting in the way. It's not necessary.
    – isherwood
    Oct 12, 2020 at 18:03
  • 1
    Store less in the loft. Those plastic totes can get quite heavy - ensure you only put the light ones up there.
    – FreeMan
    Oct 12, 2020 at 18:17
  • I believe you're allowed L/240 deflection in this situation. That's 0.5-inches on a 10-foot span. Here is a really good resource from American Wood Council that introduces the relevant concepts and a few useful data tables awc.org/codes-standards/spantables/tutorial Oct 12, 2020 at 23:29

2 Answers 2


In the same situation ( 8' span) , I glued and screwed 5/8 plywood to the bottom of the 2 X 4 s. Making something like a wide flange beam. It worked as even some furniture was stored up there ( about 7' to the peak). Plywood ,not OSB or particle board.

  • 3
    I would think that would give you almost no additional rigidity, you'd have been better off gluing the plywood to the side rather than the bottom. (Think of the orientation of the OSB web of a longspan type joist.) Oct 12, 2020 at 22:31
  • Strength/stiffness is governed by the outer fiber , that is why there are "I" and "H" beams..OSB is worthless , side thickness is almost worthless. Oct 13, 2020 at 20:45

The simplest thing to do is just sister 2x6's to the 2x4's. It doesn't need to be the full length of the 2x4's, you could make it a few inches shorter and it will be fine.

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