NZ-first Sirewall commercial rammed earth building trialled in Kawakawa for Hundertwasser project

The test wall is unveiled for a group of supporters and trustees on Friday afternoon. Photo / Peter de Graaf

A New Zealand-first construction technique being trialled in Kawakawa could open the door to Kiwis looking for new environmentally sustainable building methods, the project's backers say.

On Friday afternoon members of the Kawakawa Hundertwasser Park Charitable Trust and their Ngati Hine partners unveiled a test wall made with the Canadian-developed Sirewall technique.

It is the first step in building a $5.5 million, Hundertwasser-inspired community hub called Te Hononga on vacant land behind the famous Hundertwasser toilets in the town.

It will include a public library, council service centre, gallery and visitors' centre, while another part of the plan involves bowling the old post office and council building on Gillies St to create an atea, or town square, linking the hub with the main street.

Project co-ordinator Lau'rell Pratt said the Sirewall method, which stands for structural insulated rammed earth wall, was strong enough to meet the stringent building code requirements for public buildings such as libraries. Unlike traditional rammed earth it could also be used for multi-storey buildings.

The test wall was a chance to try out various soils, colours, pigments and decoration methods, such as indented text and artworks. It had been made with soils gathered from a 160km radius, Matauri Bay sand, and cement.

It would be the first Sirewall building and the first commercial rammed-earth building in New Zealand, Pratt said.

''A lot of people want to build with rammed earth but it isn't always strong enough. This will gives New Zealanders more options of building materials,'' she said.

Architect Pip Bolton said testing carried out so far showed the Sirewall was stronger than regular concrete, ''so the engineers are smiling from ear to ear''.

It had to be strong because Te Hononga would be built on a difficult site, a reclaimed former stream bed.

Piles could not be used because they would have to be driven up to 12m deep, making the building prohibitively expensive. Instead the building would effectively float on two concrete ''rib rafts''.

The test wall was just a few metres long but in total Te Hononga would have 80m of earth walls up to 4m in height.

''It will be playful, happy and bring a lot of joy. It will be something for Kawakawa to be really proud of,'' she said.

Pratt told supporters the building fund had hit its target just ahead of the June 30 deadline set by the Northland Regional Council, thanks to grants of $500,000 each from Foundation North and the Lotteries Environment and Heritage Fund. Fundraising would continue for fitout, artworks and landscaping.

Other funding has come from the Government's Provincial Growth Fund and the regional and district councils.

A building consent application would be submitted in a month's time with construction expected to start in October. The earth-building phase would take place in January to February next year with a planned opening in December 2019, 20 years since Friedensreich Hundertwasser opened his now-famous toilets.