Plywood Over-Floor Direction

Old 07-21-14, 12:43 PM
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Join Date: Nov 2008
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Wink Plywood Over-Floor Direction

I am in the midst of replacing a floor. I have had to rip out everything, down to the sills and have worked to get his all properly replaced. I have replaced all the joists, and sub-floor, and now I am putting in the over-floor. (I hope I am using the term correctly, this is the plywood layer that goes down over the sub-floor.)

My question has to do with the direction of the grain. I have run the first sheets with the long edge all going the same way. (If the 8 foot length of a sheet of plywood is considered the main grain, these all run the same way ie: East to West)

Now, I come down to one small section approx 39" x 48. I do not have enough of a full sheet to match the other sheets, but for such a small area, I really don't want to cut into another full sheet (especially since this is the last piece.)

My question is - does the direction of the grain really matter? I do have a small piece of plywood which would work here, but instead of matching the grain E-W, the grain would need to be turned 90 deg and run ie: North to South. (Which, as a matter of fact, matches the run of the joists, too.)

Thanks for any and all input.
Old 07-21-14, 04:49 PM
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Join Date: Jul 2007
Location: USA
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What size Ply/OSB are you using for the two layers? How big were the joists? How long was the span? What type of finished floor is going over this? Sometimes we are penny wise and pound foolish. In the scheme of the whole project, taking it down to nothing and building it back up, I assume you are building it better than it was before. You now are going to skimp on a $25 piece of ply to save $10 and install against the strength of the panel. Doing it the correct way is piece of mind. The strength of the Ply or OSB is when the panel is installed perpendicular to the floor joist.

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