Advice released: Earthquake Ratings and Retrofit of Existing Buildings, Following the Release of TS 1170.5

During February 2024, Standards New Zealand released a public consultation draft of a new Technical Specification TS 1170.5 for determining earthquake actions for new building design.

The Standards New Zealand Technical Specification Committee are currently reviewing the 800+ comments made through the consultation process and working through proposed changes. This is a considered process, and it is expected that Technical Specification 1170.5 will be published later in 2024.

In anticipation of its release, NZSEE, in conjunction with MBIE, SESOC, NZGS and NHC (as members of the Joint Committee for Seismic Assessment and Retrofit), have developed further specific advice regarding:

  • The assessment of existing buildings following the final publication of TS 1170.5 (publication date to be determined).
  • The design of seismic retrofit work in this context.

This advice has been developed to help clarify the earthquake rating system for existing buildings, and the design of seismic retrofit work, following the release of TS 1170.5.

It applies to both EPB as well as non-EPB assessments. That is, wherever seismic assessments are being carried out using the Red Book for a potential EPB or using the non-EPB version of the Engineering Assessment Guidelines, and where Earthquake Ratings (%NBS and Seismic Grades) are being used to convey life safety performance.

While the documents reiterate the current regulatory requirements for EPB buildings, their primary purpose is to advise owners and engineers who have been undertaking (and continue to undertake) voluntary, non-regulated, assessment and seismic retrofit work outside of the EPB system.

Two documents have been produced:

  • Advice for Clients and Building Owners: Extracts the key messages that are relevant for clients and building owners/users.
  • Advice for Engineers: Provides more technical background to the earthquake rating system used in assessment, and answers some common questions asked by engineers.

Read the advisory for clients and building owners Read the advisory for engineers

For buildings that have poorer seismic grades (lower %NBS ratings), both documents reiterate the importance of understanding the nature of any identified risks that have led to the reported grade (or rating)—and their potential consequences. This is important to best articulate the risks, and to help owners and stakeholders make informed decisions.

This advice does not relate to the EPB review announced by the Minister for Building and Construction in April 2024.

What is the Joint Committee for Seismic Assessment and Retrofit?

The Joint Committee for Seismic Assessment and Retrofit (JC-SAR) comprises representatives from the five organisations originally partnered to the development of the 2017 Seismic Assessment Guidelines; the Ministry of Business, Innovation and Employment (MBIE), the New Zealand Geotechnical Society (NZGS) the New Zealand Society for Earthquake Engineering (NZSEE), the Structural Engineering Society of New Zealand (SESOC) and the Natural Hazards Commission Toka Tū Ake (NHC). The committee has joint oversight of the Seismic Assessment Guidelines.