I don’t know what state you are in or council area but in NSW most council areas have a ratio of hard to soft surfaces that cannot be exceeded. It is done to minimise and control stormwater. Most developers use as much hard surface as possible – this includes any buildings so any increase in hard surface is often not possible as it will make the hard surface exceed this ratio and so the development will be non compliant. In most medium or high density areas in NSW any change to soft to hard surface needs a DA at least.
I would contact your local council and ask to speak to the duty planner. They should be able to tell you if the Owners Corporation needs to submit a DA. If the OC needs to submit a DA at the very least this will give you time to discuss the implications with other owners.