Subfloor panel orientation — lay the 8-ft length across the joists, not along them
Lay the 8-ft panel length ACROSS the joists, not along them — that puts the sheet on every joist instead of just a few. Pick the panel by span rating: it must be ≥ your joist spacing (23/32″ = 24 o.c. covers 16/19.2/24″).
What this diagram shows
A plan-view comparison of how to lay a 4-by-8 subfloor panel over floor joists. On the left, the wrong way: the panel’s 8-foot length runs parallel to the joists, so the sheet bears on only about three supports and its long edges float in the gaps between joists, where they sag and squeak. On the right, the correct way: the 8-foot length crosses the joists, so the sheet is supported on all seven joist lines at 16 inches on center. A note states that the panel’s APA Sturd-I-Floor span rating must be greater than or equal to the joist spacing — 23/32 inch is rated 24 on center and covers 16, 19.2, and 24 inch joists; the calculator hard-errors on a mismatch.
Subfloor Calculator
OSB or plywood Sturd-I-Floor sheets, screws, ring-shank nails & AFG-01 adhesive — sized off your joist spacing per APA E30 and IRC R602.3. Free.
