More foundation options for Canterbury homeowners

Building and Housing Minister Dr Nick Smith has welcomed the update to the technical guidance, Repairing and rebuilding houses affected by the Canterbury earthquakes, which provides further options for repairing and rebuilding structures on liquefaction-prone land.

“This new guidance on alternative foundation designs for building or repairing homes on land prone to liquefaction is the product of international best practice geotechnical engineering and practical Kiwi know-how developed in the course of the earthquake recovery. Its significance is that it will provide foundation options that are less expensive while still giving homeowners confidence that their home will survive a future series of earthquakes like that which struck Canterbury in 2010 and 2011,” Dr Smith says.

Land classed as TC3 has a moderate to high risk of liquefaction in an earthquake. Geotechnical investigation and engineering foundation design are required before new foundations can be built on TC3 land.

“The Canterbury land performance has been the focus of much international research so we now know more than ever about Canterbury land conditions, particularly about land damage from liquefaction,” Dr Smith says.

“The wider range of options will provide more choice so that a simpler and more affordable option can be constructed while still providing an appropriate level of protection for houses and compliance with the Building Code.”

The Ministry of Business, Innovation and Employment (MBIE) has been progressively updating the guidance as new information becomes available. This latest update is based on research data collected from recent extensive ground improvement trials and thorough peer review by international experts. The ground improvement trials tested how well various ground improvement solutions performed under simulated earthquake conditions.

The work was funded by the Earthquake Commission (EQC), MBIE, the Housing New Zealand Corporation and the National Science Foundation in the United States. Input was also provided by the Canterbury Earthquake Recovery Authority, as well as local authorities.

The research was led by EQC geotechnical engineers Tonkin & Taylor, and involved experts from the University of Texas at Austin, Brigham Young University and Oregon State University, as well as reviewers from the University of Canterbury, Cornell University, the University of California Berkeley and the University of California Davis.

Further information on the new options is available from: www.mbie.govt.nz/news-and-media/news-from-around-mbie/canterbury-technical-guidance-updated.