Who is Responsible for What?

The Body Corporate must maintain common property, as well as some things that are not on common property.

Outside of the building
Structural elements of the building (like foundation structures, roofing structures that provide protection and load-bearing walls) even if they are not on common property
Roofing membranes that are not on common property but give protection for lots or common property
Roads, pathways, gardens and lawns on common property
Facilities on common property (like swimming pools and gymnasium)
Railings or balustrades on, or near to, the boundary between a lot and common property, including the balustrade on a private balcony
Doors or windows, and their fittings in a boundary wall between a lot and common property (including garage doors and their fittings)
Utility infrastructure (like equipment, pipes and wiring) that is on common property, or in a boundary structure, or that services more than 1 lot.

The Lot Owner is responsible for:

Inside of the lot, including all fixtures and fittings inside the lot
Doors and windows leading onto a balcony that forms part of the lot
Shower tray used by the lot, even if it is not within the boundaries of the lot
Utility infrastructure (like equipment, pipes and wiring) that is within the boundaries of the lot and only services that lot
Utility infrastructure (including equipment and associated wiring and pipes) that is on common property, if it only services that lot and is a hot water system, washing machine, clothes dryer, air-conditioner or similar equipment
Fixtures or fittings, including on common property, that were installed by the occupier of a lot for their benefit (like an air conditioner)