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I’m building a second floor in my metal barn.

12’x24’Space, joists are 2”x6” Metal 16” on center & the sub-floor is 3/4” ply TnG using 1&1/4” self-tapping screws.

My questions:

What is the screw sequence on the edges & in the field?

Do I offset the 4’x8’ sub-floor sheets?

  • Since i haven't done this specific thing, I'm not going to write this as an answer, but I'd think that working from the center of the sheets to the edges would be the best to avoid any stresses due to warpage in the sheet. – computercarguy Mar 19 at 18:03
  • What sort of joists are these? – isherwood Mar 19 at 18:16
  • Isherwood, Joists are 2”x6” 14ga steel tubing, welded vertically (meaning the 2” is up, being the connecting surface to the bottom of Subfloor. The room will be used as my private, man cave: TV, drafting table, Refrigerator Books & poker table for 5! – Russ Mar 20 at 19:47
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I suspect that you're asking about interval (spacing distance) rather than sequence (order of installation). Sequence usually doesn't matter at all. Interval is somewhat subjective since this is a barn and not a dining room, so minor noise isn't really a concern. Here are my suggestions based on experience and not from any particular specification:

  • Minimum: 3 per joist - just enough to hold things down well
  • Maximum: Every 12" on the ends (5 screws) and 16" in the field (4 screws) - plenty to prevent virtually any movement

Consider using construction adhesive, which will really lock things together. I think it's overkill in a barn, though.

Yes, sheets should be staggered, ideally lapping two joists. Butt ends should never align if possible. This is to improve overall rigidity since the tongue-and-groove connection will offer support to adjacent sheets at the butt joints.

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Code minimum is 6" on the edges and 12" in the field aka to the joists in the middle of the panel

EDIT: The question has been edited and therefore my answer needs to be edited

What is the screw sequence on the edges & in the field?

There isn't one. In practice, a fastener will be placed in one of the corners to allow for any micro tweaks of the orientation before adding another fastener. Usually we would do the edges first and then fill in the field

Do I offset the 4’x8’ sub-floor sheets?

It's not required in this case but is common practice

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