Subfloor over Slab OSB/Plywood

[aclare3]

Hi,

I've ripped up the carpet in my basement and am preparing to lay engineered hardwood. I have 6 mil plastic vapor barrier to go down first. Then I have 19/32 OSB and 7/32 plywood. I had originally planned to just use the OSB and anchor it to the slab, but in order to not penetrate the vapor barrier I switched tactics to a 2 layer floating subfloor. In order to not return the OSB, I'm opting for a thin plywood underlayment sheet for the 2nd layer.

Which sheet should I do on top? I was thinking OSB on bottom and ply on top, but dont have a very good reason.

Any issues with the general approach?

Appreciate any and all advice!

 

[Floorist]

Any moisture problem? A vapor barrier can just trap moisture under it and grow mold. You can just glue the wood floor to the concrete with an adhesive that has a built-in vapor barrier.

 

[Ernesto]

Plywood holds fasteners better than OSB

 

[Nick]