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Old 01-16-2013, 10:16 AM   #1
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Installing Subfloor


I'm installing 5/8" plywood over joists (16" oc). Can anyone tell me how long the screws should be?

Thanks,

Richard

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Old 01-16-2013, 10:26 AM   #2
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Originally Posted by RichardZ View Post
I'm installing 5/8" plywood over joists (16" oc). Can anyone tell me how long the screws should be?

Thanks,

Richard
At least 0.0000236742 miles long


Last edited by hammerlane; 01-16-2013 at 10:38 AM.
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Old 01-16-2013, 10:39 AM   #3
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above is 1.5 inch...longer will not hurt but minimum I would go 1.5"
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Old 01-16-2013, 11:44 AM   #4
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You are using T & G plywood and constrution adhesive on top of the joist, right?
Why screws and not 8D ring shanked nails?
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Old 01-16-2013, 11:48 PM   #5
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Hammerlane,

So 1-5/8" would be the minimum you'd go with. Would 2" be better (if so, a little better or a lot?)? And would you recommend stepping up to 2.5" screws?

Thanks,

Richard
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Old 01-16-2013, 11:56 PM   #6
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JoeCaption,

The rest of the floor is straight 5/8" plywood, so I thought I'd stick with that. I will use construction adhesive (PL Subfloor, unless you have another suggestion). I'm using screws because I don't ever want this floor to squeak again -- may cost a bit more, but ...

At least, that's the plan. I'm open to suggestions, though.

Richard
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Old 01-17-2013, 12:08 AM   #7
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JoeCaption,

The rest of the floor is straight 5/8" plywood, so I thought I'd stick with that. I will use construction adhesive (PL Subfloor, unless you have another suggestion). I'm using screws because I don't ever want this floor to squeak again -- may cost a bit more, but ...

At least, that's the plan. I'm open to suggestions, though.

Richard
If you want your floor not to squeak then glue and screw with 2 long screws in most applications, #8 screws are sufficient. Screws should be driven at every joist on 12 centers and on 6 centers along the edges parallel to the joists. If you are counting, that results in the use of 43 screws per 4 x 8 ft sheet when installed with the long edge perpendicular to the joists, and 52 screws per 4 x 8 ft sheet when installed with the long edge parallel to the joists. Hope this helps.
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Old 01-17-2013, 12:35 AM   #8
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Epson,

That helps a lot!

Since the long side of my sheets are going perpendicular to the joists, I take it that I should put my screws every 6" along the short sides/edges, and every 12" otherwise. Did I get this correct?

Thanks,

Richard


P.S. - When I check my screw count, I get 48 screws per sheet (9 screws on each end, and 5 screws for each of the two joists in between). RH
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Old 01-17-2013, 11:16 AM   #9
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Epson,

Evidently, I need to repeat third grade math as I got neither the count nor the dimensions correct. If my count had been correct, I'd have 28 screws, not 48 screws. And that count was calculated for a 4x4 board, not a 4x8. Mea culpa.

Making the appropriate adjustments, I do indeed come up with 43 screws.

By the way, I really appreciate your including the screw count. It was absolutely a great double-check to make sure I got it right (not to mention useful in making sure one buys enough screws!).

Thx,

Richard
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Old 01-17-2013, 11:51 AM   #10
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The main reasons for using T&G is to get rid of squecks and stop and flexing between the joist.
Big mistake to not use it!
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Old 01-17-2013, 01:14 PM   #11
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A subfloor should always be T&G, otherwise you need a second layer of plywood, staggered and offset etc. Why is the rest of the subfloor square edge? There must have been a second sheet at one time.

When I re-fasten a subfloor I end up using a lot more than 43 fasteners, plus that's not counting the ones already there. I go 5-6" on the two ends and probably 8-10" on the other 5 joists of the full sheet.

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and 52 screws per 4 x 8 ft sheet when installed with the long edge parallel to the joists.
...And under what circumstances would that orientation be appropriate?

Jaz
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Old 01-18-2013, 01:16 AM   #12
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JazMan,

You are correct: there's a second sheet.

Also, I will be adding an additional layer of 3/4" T&G plywood, staggered and offset, in order to raise the floor height to match the existing floor in the adjoining room. I plan on putting 1/4" underlayment on top of the 3/4", and then finish with a loose-lay vinyl sheet.

Question: when I screw down the 3/4" T&G plywood, do I use the same approach as for when is going to tile a floor, i.e., every 4" along the edge and every 6" within the field?

Thanks,

Richard
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Old 01-18-2013, 03:46 PM   #13
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Richard,

The fastening schedule is contingent on the thickness of the sheet being installed. 3/4" underlayment requires less than thinner underlayment. I'd say 6" around the perimeter and 10-12" in the field is fine. I think the specs call for 8" on the perimeter & 12" for the field. But I like to use more.

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Old 01-18-2013, 05:37 PM   #14
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Quote:
Originally Posted by RichardZ View Post
JazMan,

You are correct: there's a second sheet.

Also, I will be adding an additional layer of 3/4" T&G plywood, staggered and offset, in order to raise the floor height to match the existing floor in the adjoining room. I plan on putting 1/4" underlayment on top of the 3/4", and then finish with a loose-lay vinyl sheet.

Question: when I screw down the 3/4" T&G plywood, do I use the same approach as for when is going to tile a floor, i.e., every 4" along the edge and every 6" within the field?

Thanks,

Richard
I would not use screws on the 1/4". Screws tend to make plywood that thin pucker. The puckers will show through even loose-lay vinyl. It is best to staple the 1/4" and don't use luan. It contains voids in the plys that can collapse.
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Old 01-18-2013, 06:56 PM   #15
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I would not use screws on the 1/4". Screws tend to make plywood that thin pucker.
Oh yes for sure, no screws for the 1/4" Use the proper staple gun if you can get one or underlayment nails.

Jaz

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