Abstract:
The New Zealand Earth Building Standards NZS 4297, NZS 4298 and NZS 4299 published in 1998 were updated in 2020 to provide for lower density earthen materials for better thermal insulation and seismic performance and a greater range of earth building techniques, and to incorporate the findings from the performance of earth buildings following the recent earthquakes in New Zealand. The 2020 Standards also provide for internal adobe veneer walls fixed to timber framing. Detailed reconnaissance surveys were carried out by a team of engineers and an architect following the 4th September 2010 Darfield Magnitude 7.1 Earthquake, the 22nd February 2011 Christchurch Magnitude 6.3 Earthquake and the 14th November 2016 Kaikoura Magnitude 7.8 Earthquake. These earthquakes were the first time that the New Zealand reinforcing approach was tested. Reinforced earth buildings constructed since the 1990’s performed well provided the overall wall bracing was adequate and detailing of the reinforcement and connections were in accordance with the 1998 New Zealand Earth Building Standards. Older unreinforced cob and adobe buildings in the areas of strong shaking suffered significant damage and needed reconstruction or repair of the walls and strengthening of the structural elements. Unreinforced pressed brick buildings performed badly, particularly following the 2011 Christchurch Earthquake, and needed dismantling and reconstruction. Recommendations for earth buildings in all high seismic zones, based on the observations of the reconnaissance surveys, included that second storeys of earth should be discouraged and that vertical and horizontal reinforcing should be provided for the earth walls. These recommendations were incorporated in the 2020 New Zealand Earth Building Standards. Full scale out of plane and in plane testing of low density adobe walls and out of plane testing of adobe veneer walls and evaluation of the test results provided the basis for incorporating these materials within the new Standards. The new Standards will encourage and enable the uptake of local earthen materials with very low embodied energy within a decarbonising building industry.
