In general terms, the controlling body such as local council will approve building plans and ensure that work is completed in accordance with the building legislation and the BCA. The BCA covers issues such as structural safety, and health and fire protection, but does not address quality of the work or finish.
The BCA set out requirements for the structural sufficiency and soundness of buildings, protection against fire, the health and comfort of the occupants. Building and planning laws set out requirements for visual and life style amenity. In some cases there will also be heritage questions. Other legislation requires approval or inspection of the installation of services, such as electricity and water.