Auckland could need an extra 20,000ha to accommodate new houses in the next three decades if its current style of new housing is to continue.

Martin Udale, ex-chief executive of McConnell Property, was commissioned by Ree Andersen, Auckland Council's regional strategy manager, to write an independent review of a report by Studio D4's Patrick Fontein and architects Jasmax on the controversial plan to ring-fence 75 per cent of all new housing within existing city limits in the next 30 years.

The council wants about 300,000 of the 400,000 new houses it expects the city to need within the next 30 years to rise within the town boundaries, a plan opposed by many commercial developers as not viable.

Udale, of Essentia Consulting Group, also questioned the wisdom behind the plan and raised the prospect of just 15 new houses built on each hectare of land, many small-lot suburban housing and townhouses, and showed how the city would need an extra 20,000ha.


But if 25 houses were built on a hectare and terrace-style residences were a big part of the mix, 12,000ha of land was needed. If 100 dwellings were built on each hectare, just 3000ha of extra land would be needed, he calculated.

Yet the Auckland plan proposed that two-thirds of all new housing development would be low-rise in the form of attached dwellings and low-rise apartments of four storeys or less.

So Udale posed the question of where all the extra land would come from and calculated that an area about half to two-thirds the current area of the Auckland isthmus could be needed.

"Unlike many other cities in Australasia, there are few areas within the Auckland urban area that present the opportunity for brownfield redevelopment over extensive areas. Auckland has about 385,000 detached homes of which about 120,000 have been constructed within the last 20 years. This paper contends that given the economic value inherent in such housing the great majority of this stock will not be redeveloped within the next 20 to 30 years."

Udale encouraged the council to consider other options in planning for future growth.

"This paper contends that a focus on achieving quality outcomes over the next 10 to 20 years will have a greater impact on achieving the level of economic performance and liveability sought by the mayor's vision than an undue focus on compactness."

Stuart Munro, Milestone Homes' co-owner, said high-rise housing was not the answer because it could not replicate the quality of life and sense of community that traditional homes offered.

"They're not the solution to Auckland's housing shortage. The majority of people don't want to bring up their families in high-rises. Our urban centres are growing and in order to accommodate this growth more land will need to be zoned for construction. Until that happens, we'll keep working to create smart and affordable homes that provide the lifestyle New Zealand families want on the land that is available."