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Navigating the Earthquake Prone Building Register with DTCE Structural Engineers

Updated: Jan 16

Every day in New Zealand, we walk a delicate balance. With the potential of a major earthquake looming over us, how prepared is your building for this inevitable challenge?


In Wellington particularly, where multiple fault lines intersect, understanding and preparing for these seismic shifts isn't just smart - it's a necessity. Join us as we explore the critical role of Aotearoa New Zealand's Earthquake-Prone Building (EPB) register in fortifying our community against the unpredictable forces beneath us. We also delve into the time and costs involved in strengthening a building, according to our past data, and end with a handy FAQ.


A Quick History of the EPB

Far more than a compliance tool, this register is integral to our mission of earthquake strengthening and community safety. It was established under the Building Act 2004, following a need to bolster our buildings resilience after a number of large earthquakes struck the country in the 20th century. Its objective is clear and critical: to identify buildings that are at risk during seismic events and ensure they are adequately strengthened to protect occupants and passersby. The EPB register is not merely about regulatory compliance; it's a proactive measure for safeguarding our communities. In a country where earthquakes are a matter of 'when' rather than 'if', understanding the register's history and purpose is crucial. It’s a vital step in our collective journey towards a safer, more resilient Aotearoa.

Earthquakes in Aotearoa: A Wellington Perspective

In Wellington, we live in a city that's uniquely positioned over multiple fault lines, including the Wellington and Wairarapa faults. This makes our seismic landscape notably intricate and precarious. The Wellington Fault, a significant geological feature, cuts through the city's heart. It's a vivid reminder of the earth's power, having moved dramatically in the past and destined to do so again. The Wairarapa Fault, which played a pivotal role in the powerful 1855 earthquake, adds to the complex seismic dynamics of the region.

Map of active faults in greater wellington region
Map of active faults in the Greater Wellington Region courtesy of GNS Science Active Faults database

While not as high risk as the Alpine fault in the South Island rupturing, these fault lines pose a significant risk of rupturing in the next 50 to 100 years, a concern that can't be ignored. While predicting earthquakes with precise timing is beyond our current scientific capabilities, geological studies and historical patterns indicate a substantial likelihood of seismic activity within this timeframe. To further quantify the risk, in 2022 GNS Science updated the National Seismic Hazard Model (NSHM), which showed earthquake hazards have increased by 50% compared to our previous knowledge. You can read more about the update to the NSHM in our blog post here: https://www.dtce.co.nz/post/summary-of-national-seismic-hazard-model


In Wellington, all this translates to living with a heightened awareness and taking a proactive approach to earthquake readiness.


The Current State: Understanding the EPB Register and %NBS

The Earthquake-Prone Building (EPB) register is an essential tool in mitigating seismic risks, listing buildings that require seismic assessment and strengthening. In the Wellington region alone, there are still 821 buildings on this register. But what determines a building's inclusion on this list? This is where the %NBS comes into play.

A selection of the buildings on the EPB register with due dates before 2030
A selection of the buildings on the EPB register with seismic work due dates before 2030

Understanding %NBS (New Building Standard) The %NBS rating is a critical metric for assessing a building's seismic performance, reflecting how well a structure can withstand an earthquake compared to a new building. A building is legally considered earthquake-prone if it falls below 34% of the New Building Standard. However, there's another important threshold to consider: the 67% mark.


This higher percentage is often targeted because many insurance companies prefer buildings to meet or exceed this standard. It's not just about meeting legal requirements; reaching or surpassing the 67% NBS is about ensuring greater resilience and often more favorable insurance terms.


Buildings between 34% and 67% NBS are often still insurable but might come with higher premiums or more stringent conditions. This dual threshold – legal compliance at 34% and enhanced assurance at 67% – guides owners in making informed decisions about the extent of strengthening needed for their properties How a Building Gets Listed:

  1. Initial Evaluation by Local Authorities: The process begins with local authorities evaluating buildings based on factors such as age, type, and construction materials. This preliminary assessment helps identify buildings that may potentially be earthquake-prone.

  2. Detailed Seismic Assessment by Engineers: If a building is suspected to be earthquake-prone after the initial evaluation, a more in-depth analysis is conducted. This Detailed Seismic Assessment (DSA) is performed by a Chartered Professional Engineer with expertise in assessing existing buildings. The DSA process is comprehensive, assessing structural load paths, the capacity of each structural element, potential inelastic mechanisms, and the building's overall response to earthquake shaking. It also considers secondary structural and critical non-structural building elements.

  3. Decision and Action Plan: Based on the DSA, the building is either confirmed as earthquake-prone or cleared. If confirmed, the building owners are then provided with a set period to enhance the building’s seismic performance. This involves either disputing the assessment results or undertaking the necessary retrofitting and strengthening work.

Finding Whether a Building is on the Register:

The EPB register is publicly accessible, allowing anyone to check if a particular building is listed. This list is here: https://epbr.building.govt.nz/


For owners who already know their building is on the list, MBIE has a very useful learning portal that can help you navigate the intricacies of getting your building off the register. This is here: https://learning.building.govt.nz/course/index.php?categoryid=9 The Path to Removal from the Register For an easier view of the whole process, we’ve created a simple diagram of the process, from receiving the initial letter from council, to final approval and removal of your building off the register:




The process of carrying out a seismic assessment and retrofit of an existing earthquake-prone building can be complex and requires specialized knowledge and expertise. It involves not just engineering assessment but also navigating regulatory requirements and, often, significant construction work.

But the outcome – a building that is safer and more resilient to seismic activity – is invaluable, particularly in a region as seismically active as Wellington. For a more in-depth look at the steps for building consent and construction, we've also created helpful road maps that can guide you in the process. Have a look at our previous blog post here: https://www.dtce.co.nz/post/mapping-out-the-building-consent-journey-from-idea-to-fruition

The Cost and Time of Seismic Strengthening

Seismic assessment and strengthening is an essential but often daunting task for building owners. Understanding the investment of time and money required is crucial for effective planning and execution, which is why we carried out a comprehensive study on our past seismic assessment retrofit projects. In this study we looked at over 42 of our past projects that we had completed over the last 5 years and asked the building owners the overall costs and time it took to strengthen. From multi-storey concrete commercial buildings, to one storey timber houses, we gathered the data.

Cost Considerations On average, the construction cost of seismic strengthening is $1,500 per m^2

However this can vary significantly based on the building's size, age, construction type, and the extent of required upgrades. Here is table with common building types and their average costs:

Building Type

Average Construction Cost per m^2

In-situ Concrete Shear Wall

$830

Timber

$1,090

Unreinforced Masonry

$2,300

This cost, while substantial, should be viewed as a long-term investment in safety and property value. It also potentially avoids the higher costs associated with building damage or loss in the event of an earthquake.

Timeframe for Retrofitting: On average, the time from our engagement to construction completion is 3.75 years However this also varied depending on the building size, construction type and the extent of the required upgrades:

Building Type

Time from first contact to construction sign off

In-situ Concrete Shear Wall

2.7 years

Timber

2.9 years

Unreinforced Masonry

5.2 years

The Time to act is now

Of the 821 buildings on the register within the Greater Wellington Region, almost 42% of them (or 350) have seismic work deadlines between 2027 and 2030. Given the large number of buildings in the Greater Wellington region that have looming seismic work deadlines, the message is clear: the time to act is now. These deadlines, set by the government, are set to ensure that buildings are safe and resilient in a timely manner. However, considering the average time required for strengthening and retrofitting, beginning the process sooner rather than later is critical.

For building owners and managers, this means engaging with structural engineering experts immediately to start the assessment and retrofitting process. Procrastination is not just a risk to the building's compliance status; it's a gamble with the safety of its occupants and the surrounding community.

How DTCE Structural Engineers Can Help

At DTCE Structural Engineers, our expertise in seismic strengthening of existing buildings is unparalleled. Over the decades, we've provided comprehensive seismic strengthening solutions for scores of buildings, tailored to each building owner's unique needs.

Our approach includes thorough evaluations and consultations, getting a holistic view to understand how the building is tenanted and what the owner wants to achieve. This enables us to customize a seismic retrofitting design specific to your needs. Our Approach: click on the following aspects of our approach to learn more about how we can help you

Comprehensive Assessments

We begin with thorough evaluations, including both Initial Evaluation Procedures (IEP) and Detailed Seismic Assessments (DSA), to accurately determine %NBS and the extent of retrofitting needed.

Customized Solutions

Holistic Overview

Collaboration with Local Authorities

Expertise in Complex Projects


Begin your journey to safety today

At DTCE Structural Engineers, our commitment extends beyond just designing structures; we aim to build a safer, more resilient Wellington. Earthquakes might be a part of our reality, but with proactive seismic assessments and retrofitting, we can significantly mitigate their impact. Our expert team is dedicated to providing support every step of the way – from initial consultation to project completion. FAQ

Why do I need to do this?

Seismic assessments and retrofitting are vital for ensuring the safety and resilience of your building in earthquake-prone areas like Wellington. Given our city’s unique position over multiple fault lines, this isn’t just a matter of compliance, but a proactive step towards safeguarding lives, properties, and investments. The Earthquake-Prone Building (EPB) register highlights buildings at risk during seismic events, aiming to fortify them against potential earthquakes

How long will it take?

Why now?

How much will it cost?

Is it worth it?


If you're considering seismic retrofitting or need expert advice on earthquake-prone building solutions, don't wait until it's too late. Contact us today to schedule a free consultation at our office. Let’s work together to ensure the safety and durability of your buildings, protect your investment, and make a positive impact in our community. Call DTCE Structural Engineers at 04 475 7933 or fill out our contact form by following the link below.

Building a safer New Zealand starts with you taking the first step.

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