The following elements are bounding elements for room area and volume computations:
- Walls (curtain, standard, in-place, face-based)
- Roofs (standard, in-place, face-based)
- Floors (standard, in-place, face-based)
- Ceilings (standard, in-place, face-based)
- Columns (architectural, structural with material set to concrete)
- Curtain systems
- Room separation lines
- Building pads
NoteFloors and ceilings are always room-bounding. These elements do not have a room-bounding property that you can turn off.
What is interesting here is that ceiling and floors will allows be room bounding (you can’t make them non-room-bounding). Ceilings are the items that could problematic especially if you are exporting to gbXML. I order to ensure you have a proper gbXML model your rooms will need to go from floor to floor. There is other workarounds (putting rooms in the ceiling space), but they are time consuming.
Maybe this is something that Autodesk can look at, or come up with better gbXML export methods.