City workers of the future may carry their office under their arms and erect it on a rooftop, award- winning architect Chris Moller says.

As cities grapple with challenges of population growth and overcrowding, he believes people will increasingly work - even live - in smaller, flexible buildings, some as little as 10sqm.

"They will be flexible, adaptable and lightweight, come in prefabricated units and be able to be carried under your arm and erected in a backyard or a rooftop," he says.

Moller likens it to living in the towns and villages of medieval Europe: "In the middle ages (an 800-year period between 600 and the 1400s) your house was also a place to make things, a domestic factory if you like, and to an extent we are going back to that model."

He believes this change will be achieved through radical new forms of off-site prefabrication such as the building system he has spent 10 years developing called click-raft. A prefabricated structure, it 'clicks' together a plywood framework - with no need for nails, fasteners or detailed joinery - using a process Moller likens to knitting or weaving.

Necessities such as cladding, power and plumbing are incorporated into the weave of the structure which comes in numbered and interlocking parts. It is designed to be put up quickly and in places traditional building methods find difficult to access.

Moller is based in Wellington but has had extensive international experience including eight years as senior urbanist in Groningen in the Netherlands. Described as an architect, designer, urbanist and philosopher, he will outline his thinking on click-raft and cities of the future as one of several keynote speakers at the INEX interior and exterior design expo in Auckland in April. www.in-ex.co.nz

He will have a 10sqm click-raft on display at the expo, one of dozens of high end architecture and design products on show.

The expo begins with a trade-only day on March 31 before opening to the public over two days, April 1 and 2. Moller is scheduled to speak on April 1.

His ideas are timely. In Auckland, the city's unitary plan is clearing the way for more intensive urban development and is calling for up to 400,000 more homes in the next 30 years, while a recent Treasury report says Auckland is currently 35,000 homes short (60,000 nationally).

Moller says click-raft is really about how to create more out of less. He says traditionally in New Zealand, housing has followed a model where people live in the suburbs and travel to the city every day for work.

He believes most homes are too big and "don't perform well" in the way they utilise space.

"Apartment living is a second model, but with the huge influx of people, particularly in Auckland, this is a system now on steroids. What I see is an option sitting between those extremes using not just city spaces more effectively, but also the space within the structure itself.

"click-raft, for example, blurs the lines between a wall and furniture - what I mean is you can use a wall as a wall, but you can also use it as a shelf. It also is about how to create space in the gaps (between buildings, on top of buildings) a city might offer.

Moller says the structures can be easily assembled - and disassembled - and it is possible to take them with you when moving.

Development of the click-raft is possible because of the shift to completely different methods of construction through digital and CNC (computer numerical control) technology. This includes the use of a computer-controlled cutter which can do the tasks of traditional carpentry-shop machines and has the potential to reduce the high cost of labour in the construction industry.

"Affordable housing is such a tough nut to crack," he says, "it is just crazy where the costs of traditional construction are going. So when we move the means of production, it fundamentally changes everything."

Moller thinks acceptance of this change will be similar to what has happened with thinking about food. This has shifted in the last 20 years to where most people understand the need for good ingredients and skills for healthy living
Moller currently has several houses and other kinds of projects on his books.

They vary in size from the 10sqm version called the C10 - suitable as a studio, office or sleep-out - to a medium unit at 30sqm and up to larger 200 and 240sqm commercial structures. They're even doing a pop-up village for a large client.

A 40sqm house his company CMA+U is working on in Wellington, will, he estimates, cost around $100,000 to build. Although it is possible for people to erect a click-raft themselves following a simple assembly process , Moller says to begin with he intends to use his own team at Makers Fabrication to do the job.

"Once ordered a C10 will only take us a couple of weeks to deliver the building as a flat-pack of pre-assembled components."

For more information go to www.in-ex.co.nz or visit www.facebook.com/INEXNZ/