The law provides that the common portions are the parts of the buildings and grounds assigned to the use or utility of all the co-owners or several of them. Thus, generally, the structure, the access roads, the premises used by all, the elevators, the corridors... are common parts.
The condominium bylaws may however contain a different distribution. For example
The private parts are the parts of the buildings and grounds reserved for the exclusive use of a specific co-owner. They are the exclusive property of each co-owner. The condominium regulations describe them in detail. It is thus the apartment of each co-owner.