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The 19 units planned for Cohaus would vary in size from studios to five bedroom homes and would have kitchens, bedrooms, lounges, bathrooms and small decks but residents would share gardens and a courtyard, storage facilities, a laundry, guest rooms and a large common room.
Gill told the Weekend Herald Cohaus was the result of a "happy accident".
He and Westergaard met Welch and Griffiths about three years ago through a mutual friend and realised they shared similar values.
Welch and Griffiths had co-owned a home with Welch's sister and her partner, where they lived together with their young children.
Gill, Westergaard and their three sons had lived in medium-density housing in Copenhagen and London and enjoyed the sense of community.
"It was nice to have neighbours who you knew and could relate to and we didn't miss all of the trappings of traditional, detached single house living that New Zealand is so fond of," said Gill.
"We didn't miss having all the yards to take care of. We didn't missing having to mow the lawn every Sunday - all that sort of stuff."
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When the Gill-Westergaard family moved to Auckland about six years ago property prices in the region had spiked to "stratospheric levels" and homes were in short supply.
Between 1996 and last year Auckland's population increased by 49 per cent, from 1,115,000 to 1,657,200, according to Statistics New Zealand figures.
The average house price in the region was $800,000 last month, according to data from the Real Estate Institute, more than 14 times the annual income of the average Kiwi ($56,472).
Gill said co-housing seemed to offer a solution to many of the region's issues.
"It's about building internal communities. It's about groups of people working together, which I think is really appealing.
"I think some of the statistics about how isolated people are in detached single houses are quite scary and the effects on people's health - rates of depression, anxiety. It's serious and it's avoidable."
About 14 per cent of people aged 15 and older said they felt lonely some, most or all of the time during the four weeks leading up to 2016 Ministry of Social Development survey about social isolation.
Solo parents and people living outside of the family nucleus were more likely to report feeling lonely than those with partners.
Several university researchers have found links between loneliness and depression, high blood pressure and dementia - and a 2010 study showed social isolation had similar effects on people's health to smoking 15 cigarettes or drinking six units of alcohol per day.
AUT Professor of Sociology Charles Crothers said housing in Auckland was quite homogeneous.
Where he lived in Point Chevalier old villas were often knocked down to make way for more modern but still detached "big bloody monstrosities" which did nothing to help with affordability or supply.
"Any form of alternative I think is great," said Crothers.
"There's been a debate for some years now about the unitary plan - should Auckland go up or should it go out? We've seen sprawls in all directions and what quite worries me is that there's some evidence that people [live] in new housing way up north or way up west and can't really afford the commute in to work. A bit more high density would be good."
Gill said Cohaus wouldn't be radically different to other kinds of housing.
"We just think this is looking at very old ways of living together. It has commonalities with Polynesian whanau customs. It has similarities to te aranga Maori design principles.
"You can find any amount of data to prove that this is good for people. It's good for your mental health, it's good for your kids, it's good for your family life."
Josh Yeats, who with his wife Julia Hanna planned to buy a three-bedroom unit at Cohaus, said he believed co-housing would be convenient and more social than living in detached homes.
"In some ways I don't think that it will be revolutionarily different, but I just think it will have all of the best things that happen in conventional places.
"I think that there'd be lots of favours and services, like baby-sitting, making meals for each other, having people over for dinner, which is really quite difficult in Auckland."
The couple, who are expecting their first child in August and own an apartment in Grafton that they rent out, wanted to live in central Auckland but couldn't afford to buy a detached house with its own garden in the area.
However, because residents would split the build costs of Cohaus, a unit in the development would be in their price range.
Barbara Grace, a 75-year-old social worker who wanted a two-bedroom unit, said she liked that the intention of connecting with neighbours was at the centre of the project and that different types of families would live there.
"It seems to really fit with increasing intensification of Auckland."
Living so close to other people would involve some negotiation, she said.
"I think everyone's going in with the intention of trying to make it work."
Moyra Elliott, 70, hoped to buy a Cohaus unit with her partner and their 3-year-old shitzu Ted. Her daughter, son-in-law, two grandchildren and their dog Rothko also wanted to live in the development but in another apartment.
Twenty-eight-year-old architectural graduate Liam McRoberts was also keen to buy into Cohaus.
Jackie Bell and Megan Edwards, both 53, told the Weekend Herald at a meeting with potential Cohaus residents this week that they considered themselves supporters of the project and were interested but hadn't committed to living there.
Most of the would-be residents met through friends or at conferences about co-housing.
Welch and Griffiths and Gill and Westergaard bought the site at 11 Surrey Cres for an undisclosed sum, but the total cost of the development would be divided when it is finished among everyone who buys into the complex.
All residents would jointly own and have shared access to the common facilities.
"The basic cost model is that all the costs get put together - the land, the interest, all the professional services, the building - and then if you're buying a 100sq m apartment and that's 5 per cent of the total floor area, then you pay 5 per cent of the total cost," said Welch.
He estimated a two-bedroom unit at Cohaus would cost about $750,000.
Cohaus would likely be cheaper to buy into than other nearby apartment blocks because its developers would also be residents so there wouldn't be any profit margins, Welch said.
Nicola Legat, co-chair of the Grey Lynn Residents' Association, said the group supported Cohaus.
Her only reservation was that the residential mental health facility Fairleigh Lodge, which is currently at the Cohaus site, would be closing in June. The facility was closing regardless of whether Cohaus went ahead.
According to documents submitted to the Auckland Council as part of Cohaus' consent application, some residents whose properties bordered the site supported the development, but others expressed concerns about privacy, shadowing and the design.
