I am wondering what "external appearance of the lot" means, please? And can Body Corporate refuse approval for the change of external appearance if it is necessary to comply with Building Code of Australia?
As far as I am aware there is no set definition for the "external appearance of the lot" - it means just that - the asthetics of the building and its surrounds. So if you plan on doing something that changes how your apartment looks from the outside then you need approval. And of course any alterations that you make must comply with the Australian Building Code.