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Discussion Starter #1
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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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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Discussion Starter #5
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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Discussion Starter #6
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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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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Discussion Starter #8
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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Discussion Starter #9
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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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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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.

epson said:
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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Discussion Starter #12
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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Tileguy
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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.

Jaz
 

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Pro Flooring Installer
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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
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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Tileguy
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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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Discussion Starter #16
Rusty Baker and Jazman,

I did plan to use staples on the 1/4" underlayment.

Followup question(s): can I get away with just the 3/4" T&G? I was worried that with all those screw holes, some would undoubtedly telescope through. Maybe, however, I'm being overly cautious. Alternatively, could I fill them in with a patching compound (sanding as necessary)? If so, any recommendations on what type of patching compound to get?

If I should go with the 1/4" underlayment, any recommendations? I've heard that I should avoid luan, but so far, luan is the only thing I can locate in my area. The lumber stores all think underlayment means subfloor plywood. Lowes and Home Depot aren't much better. Home Depot does have the following:

http://www.homedepot.com/h_d1/N-5yc1v/R-202327787/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=1%2F4%22+underlayment&storeId=10051

Home Depot also has 1/4" hardwood plywood (birch and red oak), and something called "Sandeply". Would any of the foregoing serve the purpose?

Thanks for your help,

Richard
 
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