Hi, going to put down a hardwood floor on slab on grade.
Zone 6
Here is the stackup:
6mil Plastic > 1/2" - 3/4" polyiso rigid foam > 5/8" or 3/4" T&G ply subfloor (advantec?) > Underlayment of sometype > 3/8 or 3/4 solid.

Does anyone have any experience with this approach?

I was thinking of using tapcons on 24" centers to screw the ply to the slab is that to many?

I need a low profile stackup which is why I am considering 3/8 hardwood and 5/8 subfloor.

thanks!

My best recommendation pull the manufacturers installation instructions out of the box. Read them! Follow them! If in doubt call them and ask if what you are contemplating will compromise your warranty with them.

You need a 3/4 inch underlayment/plywood for a 3/4 inch thick wood floor. Screwing this down over some rigid foam sounds iffy at best to me. You can glue the ply to the concrete but use a trowel on vapor retarder first like Bostik MVP$, then cut up plywood and use Bostick best, thats one method. Floating ply over the same MVP4 and plastic works well. I'm not a believer in fastening down the plywood. To much needless work and to many holes through the vapor retarder.