RZ1 dual occupancy changes to benefit suburb fringes with many blocks unsuited to a second home

The majority of the 800-square-metre blocks, where owners will be able to construct second dwellings up to 120 square metres and unit title the properties, are at the edge of Canberra's suburban areas, away from key services and transport links.

About 40 per cent of Canberra's RZ1 blocks, which have been zoned for detached housing, will be eligible for unit titled dual occupancies under the new criteria, set to be introduced as part of an overhauled Territory Plan.

But a map created using publicly available data shows many of the blocks will be unsuited to adding a second dwelling, for reasons including block orientation, site cover and the size of existing structures.

Zoom in and adjust the map to see RZ1 blocks highlighted where dual occupancies could be built under the new rules:

An independent geospatial specialist and former director of mapping and reporting at the federal Families and Community Services Department, engaged by The Canberra Times, determined the eligible blocks under the changes.

"I believe that while many individuals may be enticed by the potential profit from subdividing their own RZ1 block, they may also harbour concerns about the consequences," the expert said.

"For instance, they might be reluctant to see their neighbours felling trees and constructing new dwellings that overlook their own yards.

"While this appears to be one of the less controversial planning changes the ACT government can implement, it remains uncertain whether it will truly address the city's growing housing demand in the most appropriate locations for increased population density and housing expansion."

Land parcel and zoning data released by the ACT government and aligned with the geocoded national address file shows 102,269 land parcels in the territory are zoned RZ1.

After excluding land parcels smaller than 800 square metres, along with heritage areas, parklands and blocks that already have multiple dwellings, the analysis showed there were 40,245 blocks covered by the new rules.

The government had previously said there were 42,733 blocks covered by the new rules. The discrepancy could be explained by the difference between the publicly available information and more up-to-date internal information used by government planners.

An interactive map highlights which RZ1 blocks will be eligible for unit-titled dual occupancies under the new rules, allowing users to see how streets could change and inspect whether eligible blocks would be able to host a second dwelling.

The new territory plan and district strategies, released this week, charted a path to adding up to nearly 150,000 homes across Canberra in the largest shake up to the planning system since self-government.

The government said the new planning rules would provide enough space to build the 100,000 dwellings thought to be required by 2050.

A spokesman said the 120-square-metre limit on secondary dwellings would deliver modest dwellings with less of an impact on the existing streetscape.

The changes will not have instant or overnight impact on our suburbs, but additional homes on RZ1 zoned land will contribute to the Government's commitment to providing at least 70 per cent of new dwellings within our existing footprint," the spokesman said.

The territory's overhauled planning system is expected to come into effect from November 27, with the Territory Plan to be considered by a Legislative Assembly standing committee.

The government spokesman pointed to changes in the RZ2 zoned areas - allowing easier subdivisions and two-storey apartment blocks - as changes that would deliver additional housing near shopping centres and transport corridors.

Industry experts have suggested the high costs of adding a second dwelling to a block are likely to slow the uptake of the policy for RZ1 areas.

No modelling shows specifically how many dual occupancies the government expects to be built as a result of the changes.

While dual occupancy development has been allowed on 800-square-metre RZ1 blocks previously, owners have not been able to unit title the properties meaning they cannot be sold separately.

The new rules could be applied retrospectively to existing dual occupancies if the new rules on size and green space are met through a development application process.

A 2017 government discussion paper said more than half of Canberrans surveyed wanted more dual occupancies in their area.

The new Territory Plan will not rezone suburbs, but will allow two-storey apartment buildings in RZ2 areas for the first time.

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Planning Institute of Australia ACT division president Trevor Fitzpatrick this week said the institute welcomed the changes to rules governing Canberra's residential areas.

"PIA especially supports the change to the current RZ1 zone to allow unit titling of dual occupancy development on blocks over 800 square metres. These RZ1 zoned areas make up the majority of land in our suburbs and are predominately developed as single detached houses," Mr Fitzpatrick said.

"These changes will ensure appropriate protections for the character of suburban areas, whilst enabling more diverse housing types in appropriate locations. This will provide more housing choice, including the option to downsize into a new smaller home while continuing to live in the same neighbourhood."

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