OpenBuildings Designer uses Floors as a means of organizing, designing, and reporting building information. By this method, designated floors define the physical location for portions of the building relative to reference and site elevations. So the floor serves as a type of container for building elements and components in the model that include walls, doors, windows, fixtures, furnishings, equipment, structural members, mechanical components (HVAC and plumbing), and electrical equipment at a given elevation. In this capacity, floors can be used by architects, civil engineers, interior designers, landscape architects, and mechanical and structural engineers for many disciplines.

The Auxiliary Coordinate System (ACS) is an existing utility that can be used to represent floors in a building, or reference planes at a site. However, the ACS is limited in what it can do to manage an extensive, multi-tiered floor and sub-floor system within a building project. While the ACS system continues to be active within the application, the building floor management utility is available for use by building design professionals who generally think in terms of floors and not auxiliary coordinate systems. Reference planes for floor elevations, and sub-floors within a floor (ceilings, raised platforms, and top of structure for example), are created with the floor management system to manage elements and components located within floor elevations.

Note: The floor management system is available across all workset DGN files, meaning an ACS defined in one DGN can be shared by other DGNs.
You can define a set of floors and associated reference planes and sub-planes on a project-by-project basis using the floor management system. Sets of floor planes (and associated reference planes) can then be shared by the team for all designs created within a specific project. The floor management system provides these two tools, the Floor Manager and the Floor Selector.