"Joe" wrote in message
...

But I certainly dont need 3 layers.




Joe you came here asking for advice and you are getting some from people who
really have done this a few times.

Allow me to define some terms.
A sub-floor is anything that is not finishable. No matter how many layers of
plywood you put down it is all subfloor.
Half inch plwood is not a suitable surface to nail or screw anything to if
you want it to last. You need to hit the joists with your 8D nails. You are
wasting you time worring about stuff that isn't going to last no matter what
you do or don't.

You might very well need 3 layers if you plan on using vinyl tile or sheet
goods because unsanded (very smooth) plywood is not an acceptable base for
either.

You can carpet over the sub-floor as defined above. You might get away with
the new loose-lay vinyl over a tightly fitted top layer of smooth plywood.

I have a 3/4" T&G plywood sub-floor with 16" OC joists in a 1995 house.
Most of the downstairs has 3/4" hardwood over that. Every darn hardwood
nail that did not hit a joist penetrated the subfloor.

Roofing nails are meant to penetrate the deck by at least 1/8" (per mfg
instructions).

Good luck with your project.


Colbyt