Matthew Plummer (Beca) breaks down the earthquake-related legislative and regulatory changes afoot for buildings across New Zealand.
Last month’s announcement that MBIE is reviewing the ‘Earthquake Prone Buildings’ legislation has been welcomed by the property sector as a pragmatic approach to managing seismic risk in the built environment.
The proposed changes reflect the tightrope MBIE and our industry must navigate:
- What is the public’s appetite for risk, and potentially loss?
- How much can we afford to spend on resilience?
- What is the latest knowledge from earth scientists, engineers and the construction sector?
These variables change over time, so while it is superficially appealing to have a single, stable set of rules, reality will be more complex.
We are fortunate that in all matters seismic New Zealand’s engineers are highly regarded internationally, bringing world-leading technical expertise and a pragmatic approach to balancing cost and risk.
Historically New Zealand’s seismic design regulations have been updated on a generational basis, a rate of change that has been palatable to society. However, our experience of a highly shaky decade following the Canterbury earthquakes shifted the public’s view on seismic risk, and drove significant innovation from geotechnical and structural engineers. Addressing previously known vulnerabilities like hollowcore floors, unreinforced masonry (URM) walls and poorly restrained non-structural elements also became a priority.
Consequently, there are a number of changes in play. At a surface level these can be seen as confusing, so the following high-level overview aims to simplify the regulatory and legislative pathway in the coming years.
As ever, the best advice is to talk to a reputable structural engineer. They should be able to discuss how the changes impact your assets.
TLDR
| 2022 NSHM + TS1170.5 | Earthquake-Prone Buildings changes | C5 ‘Yellow Chapter’ | |
|---|---|---|---|
|
New build |
Advisory – shapes the next Building Code update, likely in 2027 |
Not applicable |
Not applicable |
|
Retrofit |
Not applicable |
The proposed EPB regime will become law, likely by 2027 |
Advisory for engineers conducting assessments, to be updated on a five-yearly basis |
The National Seismic Hazard Model and TS1170.5
- New-builds // Supports the 2027 overhaul of the Building Code’s seismic requirements
In 2022 GNS Science’s update to the National Seismic Hazard Model saw New Zealand’s earthquake hazard almost double in existing high seismic areas, e.g. Wellington and the Wairarapa, while Dunedin’s hazard has risen 2.5x, but from a much lower base. Overall, the earthquake risk in our most seismically active regions is comparable to Japan and the United States’ most vulnerable areas.
Technical Specification (TS) 1170.5 gives structural engineers design parameters that reflect the NSHM’s updated estimates. It is not part of the Building Code, but it allows engineers, contractors and developers to voluntarily test, and put into practice, designs within the context of the updated seismic hazard, and provide feedback that will eventually shape the seismic loading requirements for the next Building Code update – likely in 2027.
A Building Code update reflecting the 2022 NSHM and TS1170 feedback will only impact the design of new buildings. It will not make existing buildings ‘earthquake prone’, but market forces means it may set aspirational performance levels for retrofits to be competitive with new builds designed for the higher seismic hazard.
It is worth noting that the Building Code’s seismic components are typically reviewed every 10 years, but this has not occurred since 2004 other than adjustments made for Canterbury following the 2010/2011 Canterbury Earthquakes, as well as the Building (Earthquake-prone Buildings) Amendment Act 2016.
Proposed changes to ‘Earthquake-Prone Buildings’ regulation
- Existing buildings identified as ‘Earthquake Prone’ // To be implemented by 2027
MBIE’s announcement in September 2025 reflects feedback that the EPB system is considered financially unsustainable, with costs leading to non-compliance and ‘demolition by neglect’.
The changes will target the ‘worst of the worst’ larger buildings and risks to those outside buildings – still addressing life safety, but with a much narrower scope. Two groups replace sub-34%NBS for buildings currently deemed ‘earthquake prone’ by territorial authorities:
- Unreinforced Masonry (URM / brick) buildings
- 3+ storey ‘high-risk’ concrete buildings
Other highlights include Auckland, Northland and the Chatham Islands being removed entirely from the EPB regime, while coastal Otago is now a medium seismic risk zone (was low previously). Seismic remediation work will not trigger additional compliance work. It also excludes the need to remediate vulnerable non-structural elements (e.g. heavy ceilings). The 2004 Seismic Hazard is the basis for assessments, rather than the 2022 update, which would have raised the bar.
The proposed EPB regime will be introduced when the Building (Earthquake-prone Building System Reform) Amendment Bill becomes law, likely by 2027. Remediation for buildings still deemed earthquake prone will need to be completed within the timeframes of the 2017 legislation, albeit with the potential for territorial authorities to issue a five year extension.
Guidance on pre-cast concrete floors – C5 ‘Yellow Chapter’
- Existing concrete buildings // Ongoing updates
In March 2025 a revised version of Section C5 of the Non-Earthquake-Prone Building Seismic Assessment Guidelines was released. This is commonly referred to as the ‘Yellow Chapter’ of the ‘Red Book’ Engineering Assessment Guidelines that cover existing structures.
C5 ’Yellow Chapter’ provides engineers guidance for conducting seismic assessments of existing concrete buildings (whereas the Building Code is concerned with new-builds). It contains the latest technical information available to engineers on the performance of precast concrete floors (also referred to as ‘Dycore’, hollowcore or ‘Double T’), and reflects experience from the 2016 Kaikoura Earthquake. However, these issues are not included in the recently proposed EPB updates.
C5 is part of a wider set of guidelines for all types of structures – URM, steel, etc. that are currently being updated, a process that will be completed by the end of 2025.
It is the intention to release updates for the Engineering Assessment Guidelines every five years, reflecting their position as a repository of engineering best-practise – indeed C5 was previously updated in 2018. This regular cycle of updates will provide the industry with greater certainty as to how and when new knowledge is reviewed and considered for incorporation into the Guidelines.
It is not a regulatory requirement for building owners to undertake assessments against new updates of the guidelines. However, the latest information is often adopted by the market – for example, office buildings with previously vulnerable precast concrete floors that have been remediated are advertised as ‘C5 retrofit’, alongside their %NBS rating.
What you need to know: revised section C5 ‘Concrete Buildings’
Other considerations
- Changes have been signalled for the Health and Safety at Work Act 2015 relating to the occupation of buildings, but it is not yet clear how these might look.
- The experience of non-structural damage in the past decade and increase in demands from TS1170.5 mean more rigour will be applied to the seismic design of non-structural elements – including suspended ceilings and building services.
- The Building (Overseas Building Products, Standards, and Certification Schemes) Amendment Act intends to improve competition of supply of construction materials by reducing barriers for using high-quality building products imported from overseas.
Building Consent Authorities will be required to accept building products and methods certified overseas and recognised by MBIE. However, care should be taken to ensure these materials meet the same seismic performance requirements as those certified in New Zealand.
Author
Matthew Plummer
Senior Associate, Beca
Matthew Plummer is a Senior Associate in Beca’s Built Form team, focused on business development, with a particular focus on sustainability, resilience, and earthquake engineering. He is a Wellington Branch committee member, and his spare time is spent cooking and being walked around Wellington’s hills by his Irish Water Spaniel.
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