So just to confirm steps... are you:
1. Making the ground level room
2. Going up to the next level
3. Building your second story on top of your first story
...and then you can't place flooring in that second story room? Does the first floor's ceiling show up when you're paged up?
I did notice while testing that if I try to draw a second story room entirely off of the first floor, it drops it down and draws on the first floor even if I'm paged up. The same thing happens if I try to pick up and move the room I drew on top of the first floor. What I can do, however - if you want a floating room for a treehouse or something, is either drag the side of the second story until it overhangs the first floor, then drag the other side so it's entorely off, and it stays second floor. Or, draw first and second floors, then page down and delete the first floor - the second floor stays floating where you put it.
