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Last updated: 23 May 2017
Whether you are a building user, owner, council, or engineer, you need to be aware of how earthquake-prone buildings are managed as this may affect you.
New Zealand is extremely prone to seismic activity. Buildings need to be safe for occupants and users.
Earthquake-prone buildings are buildings that are most vulnerable in a moderate earthquake and pose a risk to people or other property. The primary objective in managing these buildings is to protect people.
On 1 July 2017 the Building (Earthquake-prone Buildings) Amendment Act is expected to take effect. It will create a national policy framework for managing earthquake prone buildings.
Until then, the Building Act 2004 contains the current framework for managing buildings for future earthquake risk. It focuses on buildings that are most vulnerable in an earthquake and does not include small residential buildings, such as most houses.
The Act currently requires each council or territorial authority to have a policy on earthquake-prone buildings, which may vary according to the local circumstances. The provisions are directed only at the worst of existing buildings.
New framework for managing earthquake-prone buildings on the MBIE Corporate website has further information on the upcoming changes.
In May 2017 MBIE held a series of presentations to help territorial authorities and building professionals plan for the implementation of the Amendment Act.
Preparing for the new system on the MBIE Corporate website has the slides from the presentations.
General information on building safety in earthquakes has information on the responsibilities of building owners to keep their buildings safe in earthquakes.
Post-emergency building assessment has information on managing a building following a major event.
Worksafe’s position statement on dealing with earthquake-related hazards is on the Worksafe website.
The Building (Earthquake-prone Buildings) Amendment Act 2016
The Building (Earthquake-prone Buildings) Amendment Act 2016 is expected to take effect from 1 July 2017. The Amendment Act will remove the requirement for territorial authorities to have their own policies by setting up a national policy framework.
The new framework will ensure the way buildings are managed for future earthquakes is consistent and strikes a balance between the following:
- protecting people from harm in an earthquake,
- the costs of strengthening or removing buildings,
- the impact on our built heritage.
There will be more information for people using buildings, such as notices on earthquake-prone buildings and a public register.
New framework for managing earthquake-prone buildings on the MBIE Corporate website has more information on the new system.
Preparing for the new system on the MBIE Corporate website has useful information for territorial authorities.
What earthquake prone means
The technical definition of an earthquake-prone building is set out in section 122 of the Building Act 2004 and the related regulations that define a moderate earthquake.
An earthquake-prone building is an existing building (other than a small residential building) that is assessed as being less than one-third of the strength required for a new building in the same location in moderate earthquake shaking, and poses a risk to people or other property.
The meaning of ‘earthquake-prone building’ will be amended in July 2017 (when the Amendment Act is expected to take effect) to clarify the two legal tests that an earthquake-prone building will need to meet. The definition will still relate to the probable strength of the building compared to a new one, and the risk to people or other property.
Definition of ‘moderate earthquake’
A moderate earthquake is a construct used by engineers to measure the performance of an existing building against a level of shaking. It does not have a magnitude.
A moderate earthquake is legally defined in regulations as:
In relation to a building, an earthquake that would generate shaking at the site of the building that is of the same duration as, but that is one-third as strong as, the earthquake shaking (determined by normal measures of acceleration, velocity and displacement) that would be used to design a new building at the same site.
How earthquake-prone buildings are currently managed
Territorial authorities are required to have developed and adopted a policy regarding dangerous, earthquake-prone and insanitary buildings under section 131 of the Building Act 2004.
As part of their policy development, territorial authorities were required to consult with their community to ensure a balance between the earthquake risk and other priorities, such as the social and economic implications of implementing the policy.
This means that the policies vary between each territorial authority.
A territorial authority’s policy must describe:
- the approach of the territorial authority in addressing earthquake-prone buildings in its area
- the priorities for that approach
- how the policy will apply to heritage buildings.
The Building Act 2004 also gives territorial authorities certain powers to manage earthquake-prone buildings. This includes being able to issue a notice to be displayed on the affected building, and requiring the owner to carry out certain building work within a time frame specified by the territorial authority’s policy.
The policies adopted by territorial authorities will be valid until the Amendment Act takes effect, when a national policy framework will be used to manage these buildings instead.
History of managing earthquake-prone buildings on the MBIE Corporate website has further information on how buildings have been managed for earthquake risk in New Zealand.