Setting 2nd floor slab/floor height independent from 1st floor ceiling height and auto roof

[JeremydV]

I'm working on a double story structure with the second story a much smaller footprint than the first floor below, including balconies on the second floor.  In order to make the roofs and pitch work, I want to raise ONLY the floor (including balconies) of the second story (the floor slab of which does not rest on any external walls of the first floor), keeping the ceiling heights below and external walls of the first floor the same, i.e. about 600mm lower than the slab  floor height of the second floor.  This will allow me the clearance I need to make the first floor roof fit with the desired pitch.  I hope that makes sense!  I cannot figure out how to do that in Pro or Architecture (I used to be able to do it in Autocad). 

 

Any advice would be much appreciated.