Advanced Engineering 2018

Flax-and-Earth Houses Enter Testing Stage

02 June 2003

Maori engineers are going back to the land in a $1 million project to build earth houses with flax reinforcing.

The project could let whanau and hapu groups build houses more cheaply than present timber construction methods, using earth and flax from their own land.

The initial research, which includes building earth and timber houses to the same floor plan for comparison, will be funded by $1.1 million over the next five years from the Foundation for Research, Science and Technology's built environment fund.

Project leader Kepa Morgan, 40-year-old associate dean (Maori) of the Auckland University engineering school, had already built two flax-reinforced earth walls in 1996-98, while heading Te Runanga o Ngati Pikiao, a tribal group near Rotorua.

""We had a papakainga [tribal housing] unit,"" he said. ""We had exhausted the cost-efficiencies of timber construction and wanted to look for alternative approaches.

""So we looked at earth. We knew it had problems with ductility [toughness], so we came up with fibre reinforcement with flax.""

The group worked out the best kind of soil to use, the best length of flax and the proportions of flax and earth. When the two walls were tested, the Machines - not the walls - failed.

For the next phase, Mr Morgan has teamed with Unitec architecture lecturer Rau Hoskins and two other engineering academics at Auckland University, Manu and Arahia Burkhardt Macrae.

They plan to build one earth and one timber house, plus earth garages and laundries.

""With timber we are looking at a 50-year time frame,"" Mr Morgan said.

""If we go to an earth structure, that's going to have a time frame of 200 years or more, and in that context it's more appropriate to the inalienable Maori land tenure.

""We are looking for cost advantages over timber and a better quality of environment inside the house - to try and get a more consistent temperature and better control of humidity, which is important for asthma and other things. Timber doesn't have the mass to hold the heat.""

He said flax was ""compatible"" with earth, whereas reinforcing it with steel or fibreglass tended to develop failures. Mr Hoskins said the flax would be cut into 8cm lengths and mixed into the earth flat on a surface. It would then be compacted into a mould and raised to form a wall, like a concrete slab wall.

Mr Morgan said the earth walls and floor of a 100sq m house would weigh about 25 tonnes.

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