Assign constructions

[Michela]

hi all
I am modelling a third floor flat therefore I have modelled adjacent spaces
on top and below it.
The "assign constructions" window does not show the flooring at all when I
select the whole flat. It allows me to assign constructions for the ceiling
and the mezzanine space but does not consider the flooring in any way.
If I go down a level and consider each room individually then I can select
the floor but in this case only one material construction is assigned to it
and even if I select the replacement which I want the software does not
take it into account.
Hope it is clear? What should I do? What have I done wrong?
Thanks
Michela