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Earthquake-prone buildings policy framework

Last updated: 19 December 2016

Whether you are a building user, owner or engineer, you need to be aware of the earthquake-prone building policy framework as it may affect you.

Buildings need to be safe for occupants and users. The Building Act 2004 sets out provisions to improve the likelihood of existing buildings withstanding earthquakes.

The provisions focus on buildings that are most vulnerable in an earthquake, and do not include small residential buildings such as most houses.

The Act requires each council or territorial authority to have a policy on earthquake-prone buildings. The provisions are directed only at the worst of existing buildings.

Buildings with less than one third of the strength of a new building would have a least 10 times the risk of serious damage or collapse when compared to a new building.

The provisions allow for councils and territorial authorities in different areas to take into account their area’s particular seismic, economic and social conditions to decide on the approach, priorities and timetable to be followed.

Earthquake-prone buildings and the law

The current legislation is directed at existing buildings (other than small residential buildings) that are less than one-third of the strength required for a new building.

It was developed in close consultation with the engineering profession and reflects:

  • lessons learned from the effects of earthquakes both internationally and in New Zealand
  • growing recognition of the inadequacies of past earthquake design practices when viewed in terms of current knowledge
  • a need for consultation between local territorial authorities, building owners and users in developing their policies.

History of earthquake-prone building law

Design standards for buildings in earthquakes were first introduced into New Zealand in 1935 following the Napier earthquake.

Significant developments in design approaches came in 1965, when three different earthquake zones were identified, reflecting the growing knowledge of the different seismicity of various parts of New Zealand. Further significant changes were made in 1976 that allowed for more variation in seismicity over New Zealand.

More importantly, the 1976 changes introduced requirements to design and detail building structures to protect vertical load carrying elements (known as the ‘capacity design’ or ‘strong column/weak beam’ approach).

Further refinements to the 1976 approach were made in 1984, 1992 and 2005. These generally reflect the increased knowledge of the seismicity of New Zealand, material properties and the response of buildings to earthquake shaking.

Many existing buildings fall short of the standards now required for new buildings.

The buildings concerned are not just those of brick masonry, which were already covered by legislation in New Zealand, but include particularly those built before 1976.

The increase in the scope of what could be an earthquake-prone building introduced in the Building Act 2004 recognised the need to keep earthquake risk reduction on the agenda.

Local policies

When the Building Act 2004 commenced, territorial authorities were required to develop and adopt a policy regarding local buildings most vulnerable in a moderate earthquake.

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.

A territorial authority's policies must describe:

  • the approach of territorial authority in addressing earthquake-prone buildings in its area
  • the priorities for that approach
  • how the policy will apply to heritage buildings.

Territorial authorities have provided us with a copy of their policies. The Act requires them to review their policies every five years to keep policies up to date with any advances in building design.

  • Sections 124 to 130 provide power for territorial authorities to act on earthquake-prone buildings and set out how this action is to be taken.
  • Sections 131 and 132 require territorial authorities to establish earthquake-prone building policies and specify how the policies are to be established, what they are to include and when they are to be reviewed.

What is ‘earthquake-prone’?

The risk of earthquake-prone buildings can be measured by comparing the assessed performance of each building to the performance required of a new building.

A key factor for territorial authorities in determining their policy for earthquake-prone buildings is likely to be the level of earthquake risk in their area – what is the probability and severity of earthquakes and what impact could they have on life and probability?

The technical definition of an earthquake-prone building is set out in the Building Act and the related regulations that define a moderate earthquake. The sections of the Building Act that refer to earthquake-prone buildings are in subpart 6 of Part 2 of the Act:

  • Section 122 and its associated regulations define an earthquake-prone building.
  • Sections 124 to 130 provide power for territorial authorities to act on earthquake-prone buildings and set out how this action is to be taken.
  • Sections 131 and 132 require territorial authorities to establish earthquake-prone buildings  policies and specify how the policies are to be established, what they are to include and when they are to be reviewed.

The definition now encompasses all buildings, not simply those constructed of unreinforced concrete. Small residential buildings are exempt from these provisions.

Definition of ‘moderate earthquake’

Under the existing legislation, a moderate earthquake is legally defined 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 site.

If you are concerned about your building’s safety in earthquakes, get professional engineering advice and act on it.

Changes to earthquake-prone buildings policy

In May 2016, new earthquake-prone building legislation was passed by Parliament. The changes are outlined in the Building (Earthquake-prone Buildings) Amendment Act.

Main features of the new legislation:

Building owners and employers can read Worksafe’s position statement on dealing with earthquake-related hazards on the Worksafe website.

This information is published by the Ministry of Business, Innovation and Employment’s Chief Executive. It is a general guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case. Expert advice may be required in specific circumstances. Where this information relates to assisting people: