Do I “have” to offset my sub floor sheets by 48″ or can I offset by 24″

xtal_01 | Posted in General Discussion on June 3, 2022 07:35pm

OK … I have a 22 x 52 ft attic.

My floor joists are at 12″

I have a stairway on one end and a 9 ft by 6 ft hole in the center of the floor (a large hatch to make it easy to bring things up).

So, I am just about to start laying 3/4 T&G advantech (just picked up a load).

Got the PL400 glue.

Problem … when I lay them out at 48″ offset (the way I have always done it), everything hits in the wrong spot.

I have just one joist between the hole (hatch hole and stairway hole) … or sheets end up just a few inches shy of the holes …

If I offset by just 24″ then things line up a lot better.

I have never seen this done … can I do this or does it need to be offset by 24″?

Thanks …. Mike

ct_yankee | Jun 03, 2022 09:38pm | #1
The reason for the "bricklayer" pattern of plywood sheathing is to minimize the effects of slight variations in panel dimensions. As far as I know there is no code requirement to do so. I would do what works best for you - a 24" stagger, or a 36" stagger - won't much matter as long as the panel joints fall on joist centerlines. But you may have to trim here and there to remedy panel variations.

finefinish | Jun 04, 2022 09:50am | #3
Hey there,
You can stagger the joints however you'd like. I'd probably rather not stagger at 12" intervals, but even that would be structurally fine. 24" would be fine and you could even switch how you stagger each row. If you are using Advantech subfloor the panels are virtually identical and you shouldn't need to trim them for inconsistencies.
ct_yankee | Jun 04, 2022 11:09am | #4
finefinish could be correct regarding the consistencies of the Advantech panels. I have no 'hands on' experience working with them, only with more pricey specialty plywood used for concrete formwork. Regardless, the 'raw' panels are trimmed and edge-routed by machines and MAY have some minor variations from panel to panel. The machines are not perfect. Good, fairly accurate, but not perfect. I have personally watched them in an Idaho factory - the process of producing plywood is mid-boggling and impressive because of the machinery developed to do so.
xtal_01 | Jun 04, 2022 12:22pm | #5
Thanks again ...snapped my lines ... got the wood on the skidloader .... tools up ... ready to start.

This Advantech looks great.

I checked a few sheets ... very consistent!

Heading out to nail down the first sheet.

Thanks again !!!!!!!!

Mike

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