Residential green zone technical categories

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TC3 announcements: What they mean for property owners (2 May 2012)

The Department of Building and Housing (DBH) has published guidance that will help engineers, building control officials and insurance assessors determine if foundations in Technical Category 3 (TC3) areas can be repaired or need to be replaced.

Read the TC3 announcement - 2 May 2012 [PDF 390KB]

Ultimately, homeowners and their insurers will need to make decisions about repairing or reconstructing foundations, with advice from a Chartered Professional Engineer. In making these decisions, they will use information gained from geotechnical drilling and off-site geotechnical analysis.

The Earthquake Commission (EQC) is leading a drilling programme for TC3 properties. Drilling is already underway in the eastern areas of Christchurch.

Note: The drilling programme provides essential information on properties with foundation or piling damage. It will not always be necessary to drill on every property in the area.

If a TC3 zoned property has no foundation or piling damage, there is nothing in the DBH guidelines or the requirements of the EQC drilling programme to stop repair work starting on that property.

Related information:

 

Overview

Land in the green zone has been divided into three technical categories – TC1 (grey), TC2 (yellow) and TC3 (blue). These categories describe how the land in expected to perform in future earthquakes, and also describe the foundation systems most likely to be required in the corresponding areas.

  • Technical Category 1 (TC1, grey) – future land damage from liquefaction is unlikely. You can use standard foundations for concrete slabs or timber floors.
  • Technical Category 2 (TC2, yellow) – minor to moderate land damage from liquefaction is possible in future significant earthquakes. You can use standard timber piled foundations for houses with lightweight cladding and roofing and suspended timber floors or enhanced concrete foundations.
  • Technical Category 3 (TC3, blue) – moderate to significant land damage from liquefaction is possible in future large earthquakes. Site-specific geotechnical investigation and specific engineering foundation design is required.

As this is an area wide classification, site specific geotechnical work will be required to determine the actual foundations required for each house in TC3 areas. In some cases this will mean TC2 level foundations will be enough in TC3 areas based on actual ground tests. This approach is common throughout New Zealand.

It is important to note that property owners only need to replace their foundations if their house needs to be rebuilt, or requires repairs to the foundations. Otherwise, no further action is needed (until you undertake major renovations that affect your foundations).

Information about foundation requirements is available on the Department of Building and Housing website.

 

Technical categories factsheets

Technical categories and your property [PDF 880KB]
This booklet, published December 2011, provides information to guide your decisions when repairing or rebuilding your property. It has has been prepared by CERA and other agencies working on Canterbury earthquake recovery to better inform residential property owners about the technical categories and what they mean. 

Technical category 1 (TC1) fact sheet [PDF 255KB]

Technical category 2 (TC2) fact sheet [PDF 255KB]

Technical category 3 (TC3) fact sheet [PDF 255KB]

Land decisions (as at 28 October 2011) [PDF 756KB]
This supplement first appeared in The Press on 29 October 2011.

 

Department of Building and Housing (DBH) guidelines

For more detailed information about technical categories and rebuilding in Christchurch visit the Department of Building and Housing website:

 

Earthquake Commission (EQC) TC3 drilling programme

The Earthquake Commission (EQC) is leading a drilling programme for TC3 properties.

The drilling programme provides essential information on properties with foundation or piling damage. It will not always be necessary to drill on every property in the area.

If a TC3 zoned property has no foundation or piling damage, there is nothing in the DBH guidelines or the requirements of the EQC drilling programme to stop repair work starting on that property.

 

Technical categories maps

View the Land Zone Technical Categories map »

PDF versions of the technical categories maps (as at 23 March 2012):

 

Questions and answers

 

Video: Green zone changes - what they mean for you

As part of the ongoing information sharing process, CERA has produced a half-hour discussion panel to cover some of the key issues around the Green Zone changes, particularly the new Technical Categories.

The discussion is facilitated by CERA chief executive Roger Sutton and involves Reid Stiven from EQC, Malcolm McMillan from the Department of Building and Housing, Mike Jacka from Tonkin and Taylor, and Dean MacGregor from IAG Insurance.

This production was put together by CERA and CTV, and was originally broadcast on Maori Television on Saturday 19 November 2011, and CTV on Sunday 20 November 2011. This production was made with technical assistance from TV3.

 

Video: Residential green zone technical categories - community meetings November 2011

CERA has produced this video of community meetings held in November 2011 to share information about the residential green zone technical categories (TC1, TC2 and TC3).

The video includes presentations from CERA Chief Executive Roger Sutton, Peter Sparrow from the Department of Building and Housing, Patrick Schofield from the Christchurch City Council, Reid Stiven from EQC, Dean MacGregor from IAG, Jason Donnelly from Tower Insurance and Peter Rhodes from AMI. The video also includes additional information from CERA Chief Geotechnical Engineer Dr Jan Kupec.

You can order a DVD of the community video by emailing us at info@cera.govt.nz  
Please write community meeting video in the subject line and provide your name and mailing address in the body of the email.

Please note a limited number of copies are available.

 

Radio interviews and adverts

Interview: CERA chief executive Roger Sutton talks about technical categories (22 November 2011)

Download the interview [MP3 3.25MB]

A three minute interview with CERA chief executive Roger Sutton, that ran in November 2011 on the Breeze radio station. Roger answers some of the most commonly asked questions about residential green zone technical categories.

Advert: Green zone technical categories (November 2011)

Download the advert [MP3 1.7MB]

A 45 second radio advertisement encouraging people to visit www.cera.govt.nz or call 0800 RING CERA for information about the residential green zone technical categories. These ads ran in November 2011 on various Christchurch radio stations.