When your city is hemmed in by mountains or ocean on all sides, finding space to put an extra 725,150 homes is challenging.

Yet according to the most recent population and household projections from the Department of Planning and Environment, the Sydney Metropolitan area will need this many new houses and multi-residential dwellings to cater for an additional 682,350 households between 2016 and 2036. That will take the city’s overall housing stock from…