# Laying second layer of subfloor



## HarryJ (Jun 10, 2011)

2nd layer of 3/4" over 1x6 slats should have buiding paper to protect from squeeks. Should line up butt joints on center of joists and try to get all screws into joists. Plywood is a better answer than osb but t&g is not necessary.


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## Bud Cline (Mar 12, 2006)

No T&G.
No glue.
Today's OSB's will take moisture the same as plywood will.


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## JazMan (Feb 17, 2007)

Hi George & Harry, & Bud,

The opinions I give come from a tile setter's view, but should be valid when installing hardwood too.



> 1) Do I really need T&G wood? A family relative had a second floor laid recently in which 5/8" ply was first laid over vinyl tile. The installers did not use T&G ply.


Not necessary, right.



> 2) Should I put a layer of felt paper between the subfloors? Or should I glue the second subfloor to the first as well as use screws? If gluing is the answer, should it be wood glue or construction adhesive?


I don't see any benefit in placing tarpaper between the subfloor and the underlayment. If anything the paper should go between the underlayment and the hardwood. Check with the manufacturer's instructions. 

The underlayment should not be glued to the subfloor, just fastened. 



> 3) Should I fasten the second subfloor into the joists? Or try not to attach to the joists? I have seen both opinions expressed in other articles.


It's best to avoid the joists and fasten into the subfloor. No problem if you use the correct length screws. Choose flooring screws that are a little longer than both layers. I don't believe it's a big deal though with hardwood.

Jaz


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## HarryJ (Jun 10, 2011)

Hi Jaz,

Ive had issues with screwing to 1x6 slats in the past thats why i recommend into joists. If there was subfloor underneath then i would agree with you


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## JazMan (Feb 17, 2007)

I know what you mean about fastening to old planks. So, I agree, if the planks are in poor condition or have wide spaces that some screws will hit air, I would then switch to longer screws and hit the joists too. 

Jaz


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## Bud Cline (Mar 12, 2006)

> Ive had issues with screwing to 1x6 slats in the past thats why i recommend into joists. If there was subfloor underneath then i would agree with you


Where Jaz is coming from is like he said; his advice is "from a tile-setters point of view."

And that is...the tile installation industry recommendation is not to screw underlayments or tile backers into floor joists in an effort to help separate the tile installation from the structure. They are to be fastened into the subfloor only. That's not to say we all agree with or understand that theory, but that's the information from the tile Gods.

In this case where hardwood is being installed I suppose it really doesn't matter.:no:


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