Technical categories information

Land classified as green means that homes are suitable for repair and rebuild.

Key points to note

• Land generally suitable for houses to be repaired or rebuilt.
• Property owners should talk directly with their insurer or EQC about repairs.
• Property owners no longer have to wait for the results of any area-wide land assessment reports by EQC or their engineering consultants Tonkin & Taylor.
• There will be some isolated exceptions where geotechnical assessments will be required due to major land damage.
• Repair and rebuilding work should take into consideration the risk of ongoing aftershocks, so some finishing tasks such as brick and driveway concrete laying should be delayed until that risk decreases.

What does Technical Category 1 (TC1, grey) mean?

Some properties in the green zone have experienced liquefaction-related land damage and considerable settlement during the sequence of Canterbury earthquakes. While land in the green zone is still generally considered suitable for residential construction, houses in some areas will need more robust foundations or site foundation design where foundation repairs or rebuilding are required.

Technical Category 1 (TC1, grey) means that future land damage from liquefaction is unlikely. You can use standard foundations for concrete slabs or timber floors. Detailed information about foundation requirements is available on the Ministry of Business, Innovation and Employment (MBIE) website(external link).

Land classified as green means that homes are suitable for repair and rebuild.

Key points to note

• Land generally suitable for houses to be repaired or rebuilt.
• Property owners should talk directly with their insurer or EQC about repairs.
• Property owners no longer have to wait for the results of any area-wide land assessment reports by EQC or their engineering consultants Tonkin & Taylor.
• There will be some isolated exceptions where geotechnical assessments will be required due to major land damage.
• Repair and rebuilding work should take into consideration the risk of ongoing aftershocks, so some finishing tasks such as brick and driveway concrete laying should be delayed until that risk decreases.

What does Technical Category 2 (TC2, yellow) mean?

Some properties in the green zone have experienced liquefaction-related land damage and considerable settlement during the sequence of Canterbury earthquakes. While land in the green zone is still generally considered suitable for residential construction, houses in some areas will need more robust foundations or site foundation design where foundation repairs or rebuilding are required.

Technical Category 2 (TC2, yellow) means that 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. Detailed information about foundation requirements is available on the Ministry of Business, Innovation and Employment (MBIE) website(external link).

Land classified as green means that homes are suitable for repair and rebuild.

Key points to note

• Land generally suitable for houses to be repaired or rebuilt.
• Property owners should talk directly with their insurer or EQC about repairs.
• EQC is currently coordinating an area-wide TC3 drilling programme. The information gained from this programme will help in making decisions about how to repair or rebuild foundations for houses on TC3 land.
• EQC and insurers, in consultation with the homeowner, will make decisions about foundation repairs or reconstruction based on professional advice.
• Testing will not necessarily need to take place on every affected property in order to get adequate information for foundation design.
• EQC has been working closely with both Building and Housing and local councils to ensure the onsite testing will meet building consent requirements.
• If additional or site-specific geotechnical information is required to determine the appropriate foundation solution for an individual TC3 property, EQC will be responsible for obtaining this information if the claims are under cap. In all other cases, the insurer will be responsible for this work.
• Repair and rebuilding work should take into consideration the risk of ongoing aftershocks, so some finishing tasks such as brick and driveway concrete laying should be delayed until that risk decreases.

What does Technical Category 3 (TC3, blue) mean?

Some properties in the green zone have experienced liquefaction-related land damage and considerable settlement during the sequence of Canterbury earthquakes. While land in the green zone is still generally considered suitable for residential construction, houses in some areas will need more robust foundations or site foundation design where foundation repairs or rebuilding are required.

Technical Category 3 (TC3, blue) means that moderate to significant land damage from liquefaction is possible in future significant earthquakes. Site-specific geotechnical investigation and specific engineering foundation design is required. There is no one-size-fits-all solution for homes in Technical Category 3 (TC3) that require repairs to foundations or need to be rebuilt. Foundations designed for homes in TC3 will be site-specific and may involve deep foundation piles.

A site-specific geotechnical investigation will identify the best foundation design for your property to reduce the risk of injury to people and damage to your property in future earthquakes. Detailed information about foundation requirements is available on the Ministry of Business, Innovation and Employment (MBIE) website(external link).

What does Technical Category 'not applicable' mean?

Technical Category not applicable means that non-residential properties in urban areas, properties in rural areas or beyond the extent of land damage mapping have not been given a Technical Category. Properties in parts of the Port Hills and Banks Peninsula have also not been given a Technical Category. This is because properties in the hill areas have always required a site-specific foundation design and are not generally subject to liquefaction or lateral spread.

Sometimes referred to as the green zone, some properties in the green zone have experienced liquefaction-related land damage and considerable settlement during the sequence of Canterbury earthquakes. While land in the green zone is still generally considered suitable for residential construction, houses in some areas will need more robust foundations or site foundation design where foundation repairs or rebuilding are required.

Normal consenting procedures will apply in these areas.

Flat land residential red zone

For properties in the flat land residential red zone areas, being zoned red means that the land has been so badly damaged by the earthquakes it is unlikely that it can be rebuilt on for a prolonged period.

The criteria for defining flat land areas as residential red zone are:

• There is significant and extensive area wide land damage.
• The success of engineering solutions may be uncertain in terms of design, success and possible commencement, given the ongoing seismic activity.
• Any repair would be disruptive and protracted for landowners.

Key points to note for the flat land residential red zone areas:

• It is not feasible to rebuild on this land at the present time.
• Wide scale land remediation would take a considerable period of time, the social dislocation of such massive works would see homeowners out of their homes for at least three years, and in some cases more than five years.
• In some areas remediation would require up to three metres of compacted fill to bring the land up to compliant height, along with many kilometres of perimeter treatment.
• In addition, a complete replacement of essential infrastructure like sewer, water, electricity and roading would be required.
• Full land repair in these areas may mean that every house would need to be removed, regardless of its degree of present building damage.
• Even if full land repair was viable, the resulting ongoing social dislocation would have major impacts on schooling, transport and employment for whole communities.

Land Information New Zealand (LINZ) is responsible for Crown-owned properties in Christchurch’s residential red zones, to find out more visit the LINZ website(external link).

Port Hills residential red zone

Being zoned red in the Port Hills means the property is in an area where there is an unacceptable risk to life safety from rock roll or cliff collapse.

In red zone areas affected by cliff collapse, there are immediate risks to life, land remediation is not considered viable and infrastructure would be difficult and costly to maintain.

In red zone areas affected by rock roll, the risk to life is considered unacceptable based on modelling by the Institute of Geological and Nuclear Sciences (GNS). The risk to life is unlikely to reach an acceptable level in a reasonable timeframe. Protective works to mitigate the life safety risk in those areas are not considered practicable, after consideration of a wide range of factors including feasibility, disruption to landowners, timeliness and cost effectiveness.The assessment of risk has been based on reports on geotechnical issues, prepared and peer reviewed by experts after extensive area-wide investigations and assessments.

LINZ is responsible for Crown-owned properties in Christchurch’s residential red zones, to find out more visit the LINZ website(external link).