Properties
Floors appear automatically as you add rooms — there's no separate 'add floor' step.
You don't create floors separately. A floor is created automatically the first time you add a room on it. So the way to add a floor is simply to add a room and give it a new floor name.
In the property creation wizard, Step 1 (Basics) has a Number of floors field. This doesn't create anything — it populates the floor dropdown when you add rooms, and caps how many distinct floors you can create.
To change it later: Property → Overview tab, find the floors strip near the top (it reads "N floors" or "Floors not set"), click the pencil icon, and update Number of floors in the "Edit number of floors" dialog. Valid range is 1–50.
Go to the Floors & Rooms tab and click Add room. The Floor field is a dropdown of suggested names ("Ground Floor", "1st Floor", "2nd Floor"…). Pick one, or click "Type a custom name instead" to enter your own (e.g. "Mezzanine", "Annexe"). Saving the room creates that floor.
If you try to add a room on a new floor beyond your configured count, you'll see:
This property is set to N floors — remove or rename an existing floor, or raise the floor count, before adding a new one
Fix it by raising Number of floors on the Overview tab. Adding rooms to a floor that already exists always works, even at the cap.
Raising Number of floors does not auto-create floors — it just widens the dropdown and raises the cap. You still create each new floor by adding its first room.
Note: lowering the number below your existing floor count is allowed and won't delete anything. Your existing floors and rooms stay exactly as they are; you simply can't add a new floor until you raise it again.