Co-housing is one of the new forms of residential expression that could be seen in Auckland under the Unitary Plan's blueprint for the city's built future.

Auckland architects Aaron Paterson and Sarosh Mulla are among the few people who say they are out-and-out delighted with the Unitary Plan.

That's because it is producing a wave of new thinking as Auckland gets to grips with the new concept of expanding up, instead of out.

Much of that new wave will be seen at INEX, the interior and exterior design expo in Auckland on April 1 and 2. Paterson and Mulla's work will be there - viewed through virtual reality headsets users say brings a futuristic scenario to startling, real life.

That includes co-housing - a new collective housing model where people, usually of like minds, band together to build private homes for sums well under market value in cities with runaway housing prices...like Auckland.

Originating in Denmark, where about eight percent of all housing is co-housing, the households typically share facilities like child care, gardens and kitchens - and the concept can even extend to shared living rooms, bedrooms and bathrooms.

In Germany, collectives financing and developing their own affordable, multi-family projects have challenged traditional house building and buying. The key is affordability - co-housing, says Paterson, finds creative ways for young families (who otherwise couldn't afford a home there) to stay in more expensive inner-city areas.

But Mulla says it's not just about money: "It's all about density but with quality and with concern for the environment. That balance between efficiency and quality is important - people have to want to live there.

"So the properties have to be weather-tight, they have to have quality materials you want to touch, they must be efficient and energy smart and not waste space with things like corridors. You need the quality so you are building something sustainable that people will spend a long time in."

Paterson says Aucklanders have typically been resistant to density housing because most of the examples they have seen have not been done well.

"So there is the opportunity now to design a better standard of living for people and to benefit the city and the community as well - bringing people together in building houses.

"There are good developers, bless them, but for many it's all about making money and there is little or no control by the end-user. So housing schemes like co-housing are becoming quite important [in other countries]."

Co-housing works on a community basis. Typically, it is made up of private homes which share enhanced facilities. They are often freehold titles owned by a company made up of the resident-builders. When someone buys into the project, they become company directors.

The design and building is aimed not just at saving money but at quality living. Among shared facilities are workshops, cinemas, roof gardens, child care, play areas, library, office spaces and - in the units themselves - shared bedrooms (and bathrooms) for guests, with options also of communal kitchens and dining.

"It's not a hippy thing," says Paterson. "You don't have to grow a beard and wear sandals. It's really just an extension of what is already happening here - like grandparents moving in with their kids or one party or another building an extra house on the section."

Housing, he says, can become not just places to live but a community magnet drawing more people into the area because of the lifestyle and plugging into the neighbourhood's existing social, leisure and economic environments: "It's not one house, one section any more; it's parcels of shared land, usually driven by people with shared interests like sustainability and a sense of community."

Paterson and Mulla are also lecturers at the University of Auckland's School of Architecture as well as undertaking research-based projects for "fascinating" clients and "design challenges." They are working on a couple of co-housing-like projects now but can't talk about them yet.

However, something close to the concept in action can be seen in Melbourne where the Nightingale housing project has hundreds of people on the waiting list, even though the development has no garages and no air conditioning - instead relying on clever design for cooling and heating.

Now spreading to Perth and Sydney, the Nightingale model is shaking up traditional real estate markets by selling quality units with shared facilities at affordable prices.

Designed alongside future residents, sustainability initiatives are a focus. The projects are funded by ethical investors whose returns are capped. The apartments are sold at below-market rates with owners only able to resell for what they paid plus any average increases in the area. The co-housing element comes with residents sharing facilities like gardens and a laundry.

Finance is the major hurdle to co-housing here, says Paterson. New Zealand's lending institutions are more geared towards the 'one house, one section' model. Overseas lenders have worked out ways - especially in big cities where density housing has long been a requirement - to enable financing of multi-resident projects where the residents are the developers.

"It's certainly time we had more discussion about enabling self-funded projects like co-housing as antidotes to the market-driven developer model.

"That's why we are happy about the Unitary Plan - we are already seeing people thinking in new ways and exploring with us different ways of maximising their site."

To see more, visit the Patterson Architecure Collective at INEX (1st and 2nd April) and step into some recent projects using cutting edge virtual reality (VR) gear.

For more information:www.in-ex.co.nz.