A challenge to build the most spacious cabin possible while still small enough to avoid council red tape has spawned a new Northland business venture.

The Tube Room started from a discussion between builder Mark Christiansen and businessman Mark Blakelock, who wanted to put some cabins on his Puketona Rd property but didn't want to go through the building consent process.

Christiansen, who is also a former building consents manager, took up the challenge and designed a tubular room the pair say is easy to build, maximises space, and is flexible enough to be used as a childen's sleepout, office, workers' bunkroom, studio or campground cabin.

Because the floor area is less than 10sq m, in most circumstances it doesn't need a building consent, while the curved walls means it has a volume 25 per cent greater than a straight-walled building of the same floor size.

Tube Room directors Mark Christiansen, left, and Mark Blakelock. Photo / Peter de Graaf
Tube Room directors Mark Christiansen, left, and Mark Blakelock. Photo / Peter de Graaf

Blakelock said The Tube Room, which is 4.1m long and 3.5m in diameter, was insulated, double-glazed and built to New Zealand building standards.

Advanced DIYers could buy the room as a kitset for $20,000 and assemble it themselves, or the company could built it on site or or deliver it for about $25,000.

Builders who wanted to use their own materials could buy the Napier-made round steel trusses.

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Blakelock said they were keen to expand around the country and had already signed up a partner in Cromwell.

The main interest so far had been from people who wanted to install eco-huts on covenanted land. Others wanted to use Tube Rooms for children's or grandparents' bedrooms or to rent out for extra income, Blakelock said.

A Tube Room is on display at the Old Packhouse Market on Kerikeri Rd every Saturday.

The Tube Room can have plumbing installed but it would then need a building consent. It would also require consent if used as a stand-alone dwelling rather than as extra space for another building.