Earthquake-prone council buildings

By , , , and - , Build 187

Councils are having to take decisions about whether to close earthquake-prone buildings, which can have an adverse impact on local communities. A new decision-making framework will help ensure a measured risk assessment.

WHEN A COUNCIL-OWNED building is found to be earthquake-prone, the territorial authority (TA) is faced with a decision about whether to suspend its occupancy. A common misconception is that, if a building is rated as less than 34%NBS and declared earthquake-prone, the building is dangerous and should be closed immediately.

Negative impact of closures

Recent history has shown that closing council buildings can have negative social and economic impacts – with facilities and services possibly not available to local communities for long periods. Businesses operating within or near council buildings may also be interrupted or forced to relocate.

Developing a consistent approach

To support a more consistent approach for decisions about earthquake-prone council buildings, BRANZ co-designed a decision-making framework to help TAs navigate their obligations around seismic safety and community wellbeing in line with the legislative timeframes for remediation.

The research was undertaken between April 2020 and April 2021 to develop a better understanding of how TAs, as property owners, currently make decisions about earthquake-prone council buildings and how this process could be improved. The research combined legal, engineering, risk management and behavioural-science expertise to co-design a decision process supporting TAs to make robust building occupancy decisions.

The legislation and regulations relating to managing council buildings were reviewed. Provisions for council management of risk relating to earthquake-prone buildings they own are directly and indirectly included in the Building Act 2004 as well as other associated regulations, the Health and Safety at Work Act 2015 and the Local Government Act 2002.

TA interviews informed framework

Staff from five TAs of varying sizes in different seismic zones representing roles in the property-owning and regulatory arms of councils were interviewed to understand current decision-making processes.

Interviewees were presented with three hypothetical scenarios about council buildings categorised as earthquake-prone and asked questions:

  • Who makes the decisions?
  • What are the key drivers of decisions?
  • How is information about seismic risk assessed alongside other risk information – including social and economic impacts?

Based on the interview findings and international best practice (ISO 31000 risk management), a decision-making framework was developed.

This was tested in online workshops with representatives from nine different TAs, then further refined using their feedback.

Community impact not considered

The interviews and online workshops with TAs revealed there appeared to be little internal discussion around risk tolerance. Of the councils involved, few had developed or adopted formal policies for decisions about earthquake-prone council buildings. Much of their decision making appeared to rest on the potential consequence of an earthquake event rather than its likelihood.

None of those interviewed explicitly considered and assessed the immediate socio-economic impacts of closing a building on the community within the decision. This is significant because it suggests that the likely short-term community impacts of immediate building closure may be over-shadowed by concerns about the potential scale of seismic risk that occurs over a much longer geological timeframe.

The result may be building closures inadvertently and adversely impacting the community. It points to a need for a clearer process that allows earthquake likelihood to be weighed against the direct consequences of suspending building occupancy.

Five steps guide decision makers

The information and feedback gathered during the interviews and workshops allowed a decision-making framework of five steps to be developed. These steps largely align with the ISO 31000 risk management process, stepping users through the risk identification, assessment and treatment phases of risk management.

The framework helps decision makers explore the actual exposure to risk in more detail. Factors such as the number of people occupying the building and the average time spent in the building are evaluated, along with the likely period before the building is strengthened. This approach is taken because risk is a function of time – the longer we are exposed to a risk, the more chance we have of the event occurring.

The framework also prompts users to consider the consequences of immediate building closure, such as the ability to deliver services by other means, impact on vulnerable communities, impact on neighbouring buildings and impact on staff.

Step five in the process combines both the exposure of people to the safety risk of being in an earthquake-prone building with the social and economic consequences of the building closure. This step is critical to ensure that TAs are balancing both their responsibility under the Health and Safety at Work Act and their duties under the Local Government Act.

A flowchart takes the decision maker through the five steps (see opposite). The decisions in the flowchart are supported by five tables that can be tailored to match a council’s current tolerance for risk. The tables help users evaluate:

  • how the building is used – the number of people generally present, for how long and how often
  • the likely time before the building is strengthened and the local seismic risk
  • the direct consequences of closure on the community, local businesses and staff.

Other hazards should be considered

Decision makers using the flowchart should do a sense check before making a final decision. Consider other hazards like hazardous substances or asbestos in the building or geological hazards adjacent to the building (for example, unstable ground) that might create an additional health and safety risk during an earthquake. The demographics of those using the building should also be considered – are they elderly, physically impaired or vulnerable? Does this change the risk to their safety?

The framework aims to give confidence to council officers, chief executives and elected members on how to meet their legislative obligations – including those in the Health and Safety at Work Act – while also minimising disruption to council activities and community services.

The challenge of managing earthquake-prone buildings extends beyond TAs as owners and occupiers of public buildings. The process and theory behind the framework presented here will be applicable to all building ownership/tenant situations.


The Managing earthquake-prone council buildings – a decision framework is available free. See also, BRANZ study report SR463 Managing earthquake-prone council buildings: Balancing life safety risks and community costs.

This work was undertaken in partnership with Resilient Organisations, Kestrel Group, the University of Canterbury’s Institute of Law, Emergencies and Disasters and Massey University’s Joint Centre for Disaster Research.

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