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I need to replace floor in a shed. Existing floor is a hodgepodge of pieces and materials (flat-edge OSB, particleboard), so I'd like to arrange floor from scratch using T&G OSB. What are the guidelines to orient the sheets so as to use minimal number of them, and produce off cuts that are more useful (e.g. half a sheet cut across vs. long narrow piece)?

I've looked for software solutions, but I could only find cut-sheet optimizing (nesting) software for sheet goods (such as MaxCut, CutList Plus etc.), but nothing obvious that would arrange full sheets in a given shape and dimensions. Whilst the question is about subfloor, same principles would apply to wall and roof sheathing as well.

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    You call it a subfloor, but if it's in a shed it's probably just the floor, right? I strongly suggest plywood. OSB will flake and chip forever if used as a finished floor. It's good product, but not for that.
    – isherwood
    Oct 8, 2019 at 12:45
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    There's only so much you can do with a 5' x 9' building when your flooring comes in 4x8 sheets... If you really want to minimize, lay it out by hand on some graph paper - each square is 1'x1', and do your figuring there. That way you're only using paper and eraser instead of expensive plywood. You could even cut out 4x8 sheets from another piece of paper to physically move them around.
    – FreeMan
    Oct 8, 2019 at 13:12
  • Also - and pictures of the "subfloor" of this space would help give even better solutions to you dilemma.
    – J Crosby
    Oct 8, 2019 at 15:01

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There are no big secrets to be had here. You start with a full sheet, tongue just inside flush, and run a row, butts centered on your joists. You then use a "beater block" to drive the second row into the first, staggering butt joints at least one joist space (ideally roughly half the sheet's length). I like a 3-4' 2x4 that I can stand on and whack with a sledge hammer. If the cutoffs are long enough, start the next row with them. If not, they're scrap.

If you expect to end up with a very narrow final row, consider ripping say 12" off the tongue edge of the first row to make the last row wider. While the t&g joint eliminates most concern, rows of 10" or less are inherently weaker. Of course, you could also block under those narrow rows if you prefer.

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  • Is thicker T&G OSB stronger in one direction? I was using some 1/2" OSB and it specifically has arrows on it indicating the strong direction so you know which way to line it up with joists/rafters. I'm not sure if the stuff made for flooring is the same. If that's the case, you can't rotate it a certain direction to make less waste - you need to run it a certain way.
    – JPhi1618
    Oct 8, 2019 at 15:34
  • My understanding is that all OSB has a strength axis. The strands are longer and the grain is aligned roughly in that direction. I assume that because in the case of t&g it's understood that the t&g edges would span the joists, no arrows are provided. Experience tells me that small fills or patches could be done in either direction with 3/4" t&g OSB without issue.
    – isherwood
    Oct 8, 2019 at 16:13

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