Building Controls Update No. 126: Revised guidance for the repair and reconstruction of homes in Canterbury

9 December 2011: The Department of Building and Housing (the Department) has issued its Revised guidance on repairing and rebuilding houses affected by the Canterbury earthquake sequence.

The revised guidance reflects new scientific and geotechnical information and knowledge about the impact of earthquakes and the effects of liquefaction on residential dwellings. It provides robust and well-balanced engineering solutions that will reduce the risk of injury to people and damage to homes in future earthquakes.

The guidance includes useful information on repairs to foundations and the construction of new foundations in green zone technical categories 1 and 2 (TC1 and TC2), assessments of retaining walls for hillside properties, chimney repairs and repairs to house superstructures, pole frame houses and masonry walls.

The guidance also applies to repairs to homes in green zone technical category 3 (TC3) that do not involve foundations. Homes in TC3 with foundation damage requiring structural repair will need further geotechnical investigation and site-specific engineering foundation design. Further investigation is being undertaken to inform the development of suitable foundation solutions for TC3.

The Department’s guidance has been developed by the Department’s Engineering Advisory Group. This group comprises experienced practitioners, including practitioners from the Department, BRANZ, the New Zealand Society for Earthquake Engineering, the Structural Engineering Society of New Zealand, the New Zealand Geotechnical Society, Tonkin & Taylor, the Earthquake Commission (EQC), GNS, and others. There has also been significant input at various stages of the process from international experts.

The Revised guidance on repairing and rebuilding houses affected by the Canterbury earthquake sequence supersedes the guidance issued by the Department in December 2010 in response to the 4 September 2010 Canterbury earthquake.

At this stage, the guidance only applies to Canterbury. The Department will consider incorporating the lessons from the Canterbury earthquake sequence into more general guidance for the rest of the country.

The guidance document can be downloaded from the Department’s website.