Room-Bounding Elements

Another interesting extract out of Revit help:

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.

You can indicate whether many elements are room-bounding by changing element properties. For example, you may want to define toilet partitions as non-bounding because they are not usually included in room computations. When you specify that an element is non-bounding, the element is not used when Revit Architecture computes the area or volume of the room or any adjacent rooms that share the non-bounding element.

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.