What is a NBS Building Rating?

Published 04 April 2023

The Initial NBS, or New Building Standard rating, is a high-level assessment of the seismic risk of a building, compared to a building built to the current building code. It is not a prediction of how a building will survive in an earthquake/seismic event. It’s purpose is to inform building owners how vulnerable a building is in a seismic event.

The NBS rating system came into effect in July 2017, called the Building (Earthquake-prone Buildings (EPB)) Amendment Act 2016. It introduced major changes to the way earthquake-prone buildings are identified and managed under the Building Act, based around knowledge learnt from past earthquakes in New Zealand and overseas. It is applied to both older buildings and existing modern-day buildings. Local Councils (or Territory Authorities (TA’s)) have developed schedules of buildings deemed to be earthquake-prone, based on the NBS ratings.

The Initial NBS rating for existing buildings involves a high-level (qualitative) desktop assessment of the buildings seismic elements. It takes into consideration the seismic elements of the building, its height, age and the seismic risk of the buildings location.

The Seismic Risk Areas Map highlights three different zones of seismic risk as assessed in New Zealand – high, medium & low. Each of these three zones have different reporting standards and timeframes for when seismic upgrade work needs to be carried out. 

It needs to be noted that the Initial NBS rating is simply the first step in assessing a buildings seismic vulnerability as part of an Initial Seismic Assessment (ISA). Following this is a Detailed Seismic Assessment (DSA), which is an assessment based on engineering design calculations (quantitative), similar to the design process for a new building. We will go into more detail around ISA’s and DSA’s in the next article.


So how do I know what rating my office or building should have?

Some buildings require certain minimum NBS ratings based on the buildings use. For instance, a hospital requires a higher NBS rating as it needs to remain operational in an earthquake so at risk patients can be effectively evacuated. This is indicated by the buildings Importance Level (IL) rating, which we will cover in another article.

For the standard older office environment, the typical rating is likely to be below 67% NBS.

A building rated less than 34% would be identified as being an ‘Earthquake Prone Building’ and it would need to be retrofitted to a higher level of New Building Standard within the timeframes listed in the above table. This doesn’t mean there aren’t occupied earthquake prone buildings around. The law does not insist these buildings be immediately vacated, but there could be consequences under Health & Safety in the Employment Act if owners don’t take steps to minimise hazards in the workplace.

A building with a rating between 34% and 67% is categorised as an earthquake risk building under EPB Amendment Act. Many building owners consider a building with a NBS rating above 67% to be an acceptable seismic risk.

Depending on your businesses priorities you may have a minimum standard you require from your office environment. Moving into or building a completely new building isn’t always feasible. There are several office providers who are retro fitting their offices to meet higher NBS ratings. Greenstone Group have extensive experience in project managing office retrofits and seismic strengthening of existing and heritage buildings, such as 105 Carlton Gore Road, Auckland and 18 Willis St in Wellington.

The NBS rating system is an important tool in understanding the safety of the environments we work and live in. Although there is no immediate legal requirement to close a building because of a low NBS rating, the %NBS assessment is also used by insurance companies, portfolio managers, tenants and government agencies to determine risk which could impact insurance rates and building rents. In the end it comes down to a question of safety. New Zealand is prone to seismic activity and ensuring the safety of occupants and users should be paramount.

If you want to know more about upgrading your buildings to improve the NBS assessment, then please contact us. We can help you navigate through the various processes, investigate options, costs and the timeframes involved.

1: Progress toward identifying potentially earthquake-prone buildings 2021