This construct is intended for objects that are part of the building core (like walls, doors, etc.), excluding the stairs and possibly the toilet rooms. The stairs should be drawn in the separate stairs construct. Toilet rooms, if the layout is the same on all levels, can be drawn here and copied to each level. Otherwise, they can be created as an element file like the Typical Toilet Room element file (included in this Commercial Template Project), and then dragged into the Core construct file.
If you do not wish to have a separate core construct, core geometry can be drawn in either the Shell or Interior construct files instead. If you do this, delete the core construct(s) from the project.
The various Core constructs are referenced in the Floor Plans, Composite Model and Section View files.