Watch: Prefab of 43 Auckland homes like Lego for adults

Homes are being built in Wellington for Auckland's under-supplied market in a Lego-like technique, which sees them being trucked north as separate units and assembled on-site.

An Auckland development business is building the pre-fabricated homes on what were single-home sites around the city, planning hundreds of new places via its fast-track method.

Gary Gordon and Claire Beazley of Legacy Property's Solution Street showed how three townhouse residences built at Trenthan north of Wellington were lifted into place on a Manurewa site.

"The units were built by Matrix Homes," Gordon said of the project where ground works took a few weeks.

The two-level houses came here on trucks as box-like units. The first level can be seen being placed on foundations, then the second storey, with its pitched roof, is craned on top.

Matrix has a factory production-line system, building different modules in the former General Motors car assembly factory. "Inefficient practices and uncompetitive markets have inflated the price of Kiwi homes," Matrix says, and it wants to change that.

Gordon said Matrix was not the only prefab business he was dealing with. Mangere's Stanley Group - a partner of PrefabNZ - was also building for Solution Street, he said.

Solution Street is aiming to sell its prefab places to first home buyers, targeting Auckland's cheapest suburbs where it is applying the fast construction techniques to keep costs down.

Beazley said Solution Street was building 43 two- and three-bedroom homes. Gordon said these were in Manurewa, Glenfield, Glen Eden, Mangere, Panmure and Henderson and the business was aiming to sell most in the $500,000 to sub-$700,000 range.

Months could be saved off standard housing construction time frames, he claimed.

"The ideal time for these projects would be three months to get resource consent, two months to pre-fabricate during which times site would be being carried out then one month on the site, so about six months all up," he said from Takapuna offices.

Beazley said Solution Street had already sold 26 homes. It has 17 for sale and the average cost was $600,000, she said.

"The total cost of houses sold to date is $15m. We also have several new sites under contract," she said.

Pamela Bell, PrefabNZ chief executive, said her organisation was in full support of the use of offsite construction techniques.

"These deliver quality housing solutions to those who need them. The benefits to the end user are controlled outcomes such as reduced time and increased quality, while also saving materials and enhancing worker safety," Bell said.

Solution Street has recently joined PrefabNZ.

Last August, Fletcher Living unveiled its house-in-a-day technique at Hobsonville Point.

Read more: Auckland house-in-a-day: Fletcher unveils high-speed process

A 170sq m $800,000 three-bedroom home was put up between 7.30am and 5pm on a day by Fletcher Living.

Dan Heyworth, chief executive of The Workshop Company, showed off two prefab houses being built in the old Alloy Yacht factory at Henderson. Gantries once used to hoist marine components are now being used to lift heavy housing parts.

Read more: 'It resembles a doll house assembly plant': the Auckland factory at the centre of the prefab revolution

Heyworth wants to build new Housing NZ Corporation homes and some of the 100,000 KiwiBuild places housing minister Phil Twyford plans during a 10-year period.

Gordon, whose Legacy has been going for 16 years, said it was unclear whether KiwiBuilt would be complementary to Solution Street "or a competitor." Legacy had built more than 1000 residences, mainly in Auckland and Christchurch, in that time, he said.

Gordon owns 70 per cent of Legacy, whose lenders include NZ Mortgages & Securities.

"We want to build 200 new places a year in Auckland," he said of Solution Street's aims. "All of that will be infill, none of it on greenfields sites. We hope to sell each place for around $500,000 to $600,000 each. In each case, we're buying a single house and a large site. There's no limit to the number of sites you can buy. But more importantly, we're buying where there are existing amenities," he said referring to utilities in established suburban areas.