After adding levels to my current project and loosing the vaulted ceiling that I had added for the living room area I started searching the User's Guide, the in program help and Google for a concise summary how elevation, floor thickness and height really work. After playing with a test drawing I found the following additional information:

• Elevation is the level the furniture objects will be placed and floor surfaces of rooms (if enabled) will be shown. (That one is obvious.)
• Floor thickness indicates how thick the floor is. This thickness reaches below the elevation and is seen from lower levels with the color or texture that is used for the floor of the corresponding room when looking up from lower floors. A room floor effectively becomes a polygon extruded below the surface with the given thickness. Walls from higher levels also reach below the elevation of their corresponding level with the assigned colors or textures visible.
• Height is used to draw ceilings at this height for rooms at the current level, except at the topmost level, when the wall-height is used to calculate the ceiling height for rooms that are nearby. The ceiling is always a polygon with zero thickness.

Did I get that right, or am I missing other effects?