The zoning changes will allow dual-occupancies to be built on blocks that are 800 square metres or bigger, though onlookers expect few owners to take up the option.

Owners of residential blocks that are 800 square metres or bigger will be able to split their block into a dual-occupancy.

One of the two dwellings will be limited to 120 square metres of floor space to improve affordability.

About 45,000 blocks may be eligible, mostly in Tuggeranong and Belconnen.