Development of a flax-fibre reinforced, cement-stabilized rammed earth housing solution (Uku) for rural Māori communities

Abstract

The research presented in this thesis develops the Uku flax-fibre reinforced, rammed earth housing method. The research was conducted using a kaupapa Māori research methodology and integrated Māori culture, structural testing of Uku, and the Mauri Model decision making framework, to empower Māori from the rural community of Ahipara, New Zealand, to implement a 102 m2 Uku dwelling on their ancestral lands. The thesis is presented in three parts. The first part involved gathering the local perspectives in Ahipara regarding the holistic sustainability of rural Māori housing solutions. The second part reported investigations into the material strength and seismic performance of Uku test specimens and full-sized panels. Finally, the third part documented the process of the Ahipara whanau designing and building an Uku dwelling. Using the Mauri Model decision making framework, a survey was conducted to ascertain the perceived holistic sustainability of Uku rammed earth and light timber-framed housing as a rural Māori housing solution. A holistic assessment was attained by using an intrinsic measure of sustainability ‘mauri’ to evaluate the housing methods in the four dimensions of environmental, social, cultural and economic. Individuals from five groups, the rural Māori community, environmentalists, Far North District Council, Community Housing Aotearoa, and Housing New Zealand Corporation, were surveyed. The Uku housing method was determined to be sustainable by individuals belonging to all five groups surveyed whilst the light timber-framed was perceived to be sustainable by two groups and unsustainable by the remaining three. Compression and flexural tests on Uku rammed earth specimens were conducted. The test results provided data upon which the rate of strength gain rate could be predicted and improved understanding regarding the relationship between material density and strength. Comparisons of flexure and shear strengths with compressive strength were made to evaluate empirical relationships specified in the New Zealand Earth Building standards. The assumption that 10% of compressive strength was equivalent to the flexural strength of rammed earth was supported by the test results, and the assumption of 7% of compression strength being equivalent to the shear strength of rammed earth was found to be conservative. Pseudo-static cyclic tests conducted on full-sized Uku rammed earth panels, and a 3-panel wall assemblage, showed the panels had considerable non-linear strength capacity. The ductility measured from the load-displacement plot of the Uku assemblage was 1.5 and 2.8 in the two directions of loading whilst the results for single panel tests ranged 2.6 to 5.8. A structural ductility value of 1.25 was thus recommended for the design of Uku structures. The testing of panels, both in the laboratory and onsite in Ahipara, showed the importance of onsite testing. The laboratory panels were 31-50% stronger than predicted while the fourth onsite panel tested reached a maximum of 90% of the design load. The first three onsite panel tests exhibited low strengths due primarily to issues of onsite test methods, onsite construction methods, and worker experience. The onsite test experiences were invaluable as they helped to identity unavoidable issues when building and testing in an outdoor, isolated environment, with individuals from the local community. A test setup comprising of a large excavator as a reaction frame was described and is recommended for future onsite tests of Uku rammed earth walls. The implementation of an Uku dwelling, which was driven by Māori from Ahipara and was conducted in adherence to Māori values and cultural practices, was used to identify and develop solutions to common housing obstacles experienced by Māori when developing on their ancestral lands. In the Appendix documents which would assist other Māori whanau develop Uku housing on their ancestral lands have been shared and include, communication with the Far North District Council regarding building consent issues, a copy of the main engineering calculations for the Ahipara Uku dwelling, and a full set of architectural plans. The doctoral research has shown that the use of a kaupapa Māori research methodology was an effective way to conduct research within a Māori community, and to develop a housing solution for their benefit. The Uku housing method was also shown to be an appropriate and viable housing solution through the successful implementation of an Uku dwelling in Ahipara during the doctoral research period.