I want to install some prefinished  ash hardwood floor in my office over a concrete slab.   It is solid wood 9/16″ thick tongue and groove.  It is not the interlocking floating floor kind which I have never used.  The only way I know how to do this is to glue  and nail down 3/4 CDX  first and then nail the hardwood to the cdx.  But my question – is there a way to do this without the cdx?  Like glueing it all down somehow? Any ideas are appreciated. thanks