Mobile bach just needs a tractor to find a new vie

A bach has been built in the Coromandel that can be moved around on its site according to shifting sand dunes or the owners' needs.

Ken Crosson, of Crosson Clarke Carnachan, said he designed the Whangapoua holiday house as a modern version of a traditional seaside hut but because it was on a site within a coastal erosion zone, authorities deemed any new structures must be removable.

"Their coastal erosion zone means if you build there, you have to have a demountable house. You need to prove you can move it out," Mr Crosson said.

"A lot of the Coromandel coast has designations on it now," he said, meaning houses must be able to be removed.

A planning expert at Thames Coromandel District Council said the sand moved massively so development setback lines controlled buildings on the waterfront under building rules imposed by Environment Waikato.

"It's more of a building issue than a planning issue but it's about having something that's relocatable," she said.

Environment Waikato's report on the issue said the council allowed relocatable buildings to be developed between 30m and 60m "from the toe of the dune".

Mr Crosson designed a pair of thick timber sleds, laid beneath the two-level lightweight building, enabling the owners to hook it to a tractor and tow it.

He said the family who commissioned and owned the house had not yet moved it but might do so if they ever decided to build another house there.

He said he was thinking of a lifeguard observation tower or fishing hut when he worked on the design.

The tiny house has been commended in an international design competition by Architectural Review magazine.

Judges praised the structure and noted its unusual mechanisms and fittings for opening enormous screens which were "unapologetically industrial, the structure gutsy and exposed".

Mr Crosson said a family of five could stay at the bach, which is like a large cabinet and designed to close up against the elements when not being used.

Rough macrocarpa cladding blends into the landscape when the place is unoccupied and the back of the bach is clad in "flat sheet", a cheap metal cladding used in holiday homes.

A double-height shutter winches up like a concertina to form an awning, shading the efficiently planned interior.