I have an install in a Solid Oak flooring in High rise Condo with Concrete floors(not gycrete) I Can Not use a air gun (condo rules) to apply the plywood to the concrete floor.I can not use floating engineered floor because floor is very uneven in many spots ( many high and low spots) in the condo
Here is what I want to fo:
1-Glue down cork 1/4 cork
2-lay (not nail) 2 3/8" pieces of plywood crisscrossed or 1 3/4" over cork -
3-install felt paper over -plywood
4-Solid 3/4' oak flooring
4-Minwax stain and Syteko(water base) finish

Question- can you just float the plywood and not nail it
Question which is better to use 2 3/8" crisscrossed or 1 3/4" plywood ?
Question is felt paper nesccessary?
Question is Minwax stain good?
Question- Is Syteko water base just as good as oil based ( using water because of minimizing the strong smell in condo)

1) The subfloor needs to be flat. Installing cork and plywood doesn't mean you can get away with an uneven slab. It sounds like your going to need to figure on floating, and or, grinding and floating.
2) I would prefer to install a floating subfloor, 3/4" ACX, cut into 16" strips, relief cut, & staggered, with expansion space inbetween panels & perimeter. There's no reason to glue the cork to the slab.
3) IMO felt paper is necessary, for ease of installation.
4) I'm not a s&f guy, but I understand Bona dry fast is the stain of choice. Couldnt tell you about Synteko, but I'm sure the guys with more s&f experience will let you know.

Floorologist,
What do you mean "cut into 16" strips"? 48" x 16" or 96" x 16".
How do you keep the boards attached to one another?
Also, how often and how deep do you use the relief cuts?

Willie, first of all, address the slab flatness and correct that by grinding/patching as needed. Secondly, before installing the subfloor, install a vapor barrier over the slab (6 mil poly, etc.)

Regarding floating the subfloor as Floorologist described, you would cut 3/4" ply in to 16" x 96" sections. Relief cut 3/8" deep every 12". Lay perpendicular or diagonal to direction the hardwood is to lay. Stagger the plywood by 2', 3/4" expansion around perimeter and vertical obstructions. The panels are not attached to slab...they loose lay (float).

You're other option, which may be a little more money but less labor intensive (less cutting, no relief cuts), is to float 2 layers of 3/8" ply. Again, correct the slab flatness as necessary, install your vapor barrier. Then, lay the first layer of sheeting in a direction parallel to the walls, leaveing 3/4" expansion space at perimeter and vertical obstructions and 1/8" gap between sheets. Then lay the second layer perpendicular or at a 45 degree angle to the first, same spacing for expansion (3/4", 1/8") as first layer. Fasten by stapling or stapling and glueing (construction adhesive) the second layer to the first.