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Mounting 8' plywood across studs?

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  • Dec 21st, 2020 2:34 pm
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[OP]
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May 6, 2005
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Squamish

Mounting 8' plywood across studs?

I am in a new townhome finished last year, so it's modern... it seems the studs are 24" apart, though there may be a few extra.

Obviously a 4x8 sheet at length matches exactly with the studs (I'm guessing that's not exactly a coincidence?) but am nervous about mounting across 4 studs as I worry about being able to reliably mount at basically the very-edges of the plywood, hoping the studs are in fact at properly-measured distance. Should this be totally fine or should I aim to shorten my plywood and just spread across 3 studs with some overlap (would much rather use full 8' length)
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Deal Addict
Dec 19, 2009
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Cut the plywood in half and spread it across 2 studs each.
[OP]
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May 6, 2005
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pootza wrote: Cut the plywood in half and spread it across 2 studs each.
Don't I just run into the same problem, or have a gap in the middle?
[OP]
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engineered wrote: What's the plywood for? You can just center it over 3 studs and secure it. That would be plenty sturdy.
My "french cleat wall" that I've been thinking about forever, without nearly as much DOING :)

Wanna put plywood as a backer instead of just the bare wall, then attach my french cleats to the plywood. So whole thing would be 8' long and probably about 6' tall (though will prob leave at 4' for a while)
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Nov 26, 2003
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For mounting the plywood, you should be able to get it onto 4 studs if they're all spaced 24" on-center. The screws wouldn't be at the "very edges of the plywood" - the screws should be inset from the edge of the plywood, AND what you want is for the screw to hit the center of the stud. This way the plywood is securely fasten to the stud.

One other thing is to use adequate screws to attach the plywood to the studs so it can handle whatever weight the french cleat wall needs to support.
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Dec 6, 2020
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Kaitlyn wrote: Obviously a 4x8 sheet at length matches exactly with the studs (I'm guessing that's not exactly a coincidence?) but am nervous about mounting across 4 studs as I worry about being able to reliably mount at basically the very-edges of the plywood, hoping the studs are in fact at properly-measured distance.
Stud spacing is given from center to center of each stud. The dimensional lumber used in framing is 1.5" wide. If you want to attach a 4x8 sheet of anything (plywood, drywall, etc), to the studs, you will have 3/4" of wood available on each end.

Chances are, the exterior sheathing on your house is made of 4x8 plywood sheets nailed to the studs and the inside drywall is made of 4x8 sheets nailed (or screwed) to the studs. The studs will have been placed accurately enough for this to work.

Even if you can only screw the plywood into two studs, you shouldn't have any problems. A 3" #8 wood screw is rated for around 50 lbs shear load in this application. Put up a 1/2" piece of plywood with 8 screws--even if they're only connected to two studs--and it's not going anywhere.

(If you need to hang more than 400lbs off a wall, then it's time to call an engineer....)
[OP]
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May 6, 2005
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middleofnowhere wrote: Stud spacing is given from center to center of each stud. The dimensional lumber used in framing is 1.5" wide. If you want to attach a 4x8 sheet of anything (plywood, drywall, etc), to the studs, you will have 3/4" of wood available on each end.

Chances are, the exterior sheathing on your house is made of 4x8 plywood sheets nailed to the studs and the inside drywall is made of 4x8 sheets nailed (or screwed) to the studs. The studs will have been placed accurately enough for this to work.

Even if you can only screw the plywood into two studs, you shouldn't have any problems. A 3" #8 wood screw is rated for around 50 lbs shear load in this application. Put up a 1/2" piece of plywood with 8 screws--even if they're only connected to two studs--and it's not going anywhere.

(If you need to hang more than 400lbs off a wall, then it's time to call an engineer....)
Engineer schmengineer!

Thanks for that though - yeah, obviously the drywall had to go up! Thanks
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Apr 11, 2006
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Mississauga
I think you go with three studs. That way all three studs are mounted to the heart of the plywood as opposed to the edge.

I don't imagine you're putting really heavy things on your french cleat wall anyways.

And then you go with five screws on each stud for 15 in total and you'll be good.
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Dec 18, 2017
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London, On
You can also mount another stud or blocks to the side of the stud at the end of the plywood if the measurements are a little off.
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Feb 26, 2019
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Ottawa
Sounds like a good excuse to buy a stud finder. Best part of a project like this is the excuse to add a couple tools to your collection!
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Oct 23, 2017
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GTA West
Kaitlyn wrote: I am in a new townhome finished last year, so it's modern... it seems the studs are 24" apart, though there may be a few extra.

Obviously a 4x8 sheet at length matches exactly with the studs (I'm guessing that's not exactly a coincidence?) but am nervous about mounting across 4 studs as I worry about being able to reliably mount at basically the very-edges of the plywood, hoping the studs are in fact at properly-measured distance. Should this be totally fine or should I aim to shorten my plywood and just spread across 3 studs with some overlap (would much rather use full 8' length)
Going across 4 studs gives you ample support if they are 24" apart - that is a span of 72" for an 96" panel. I always avoid putting screws or nails at the edge of a plywood panel when used like this, since it can splinter the edge, etc. You can verify the stud spacing with a stud finder.

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