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· Registered
59 Posts
Discussion Starter · #1 ·
I am building an 8 x 12 shed. I am planning to have 2x6 joists 16" oc. I am using 3/4" tongue & groove plywood for the floor.

Is there any reason to lay the plywood in one orientation or the other?

I could lay 3 sheets with the 8' dimension of the sheet matching the 8' dimension of the shed. Or, I could turn them 90 degrees, which would require cutting the sheets.


(not to scale)



· Registered User
11,730 Posts
As konstruction said: perpendicular to the joists. Try to span minimum 1 middle joist (32" wide cut), with the smallest piece. Be safe, GBAR

· Old School
3,634 Posts
Thanks, I knew it was typically done that was but I wasn't sure if there was a reason.
There really is a reason. Well, a couple of them, actually.

1. - Cheaper plywoods are laminated in such a way that there is more strength against breakage in the longer direction. More expensive plywood doesn't seem to have this problem. Flooring plywood is the cheaper stuff.

2. - Perpendicular spanning of floor joists helps to negate the varying relative heights of all the top surfaces of the joists. They do not often create a flat, level plane upon which to place flooring. If your joint in your first drawing happened to fall on a joist that was either high (or low) in comparison to all the others, you would have a very pronounced rise (or a dip) in that area of your floor. Going crosswise to the joists reduces the prominence of such a deviation.
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