What you need to know: Revised Section C5 'Concrete Buildings'

Key points

• When carrying out seismic assessments of potentially earthquake-prone buildings, engineers must use the current 2017 Engineering Assessment Guidelines (the Red Book).
• The Non-Earthquake Prone Building Assessment Guidelines (the Guidelines) provide engineers with guidance on how to conduct seismic assessments of concrete buildings outside the earthquake-prone building system.
• A revised version of Section C5 ‘Concrete Buildings’ of the Guidelines is now available to industry on Design.Resilience.NZ
• The revised Section C5 incorporates the latest engineering knowledge on how concrete buildings perform in earthquakes, and supersedes the 2018 Yellow Chapter. 
• Work is underway to update other sections of the Guidelines in 2025. The final Non-EPB Seismic Assessment Guidelines are expected to be published at the end of the year.
• Once the final Guidelines have been published, the Joint Committee for Seismic Assessment and Retrofit will start a five-yearly guidance update schedule, aiming for the next update to the Non-EPB Seismic Assessment Guidelines in 2030. 
• It is not a regulatory requirement for building owners who have undertaken an earthquake-prone building assessment using the Red Book to carry out a retrospective or additional assessment with the Guidelines.

Background

The 2017 Seismic Assessments of Existing Buildings – Technical Guidelines for Engineering Assessment (known as the Red Book) are mandatory technical guidelines for engineers to carry out engineering assessments on potentially earthquake-prone buildings. They must also be used by engineers for all seismic assessments under the earthquake-prone building system.

The Non-Earthquake Prone Building Seismic Assessment Guidelines (Guidelines) incorporate updates that represent the latest engineering knowledge about how buildings are likely to perform in an earthquake. The Guidelines are not referenced in EPB methodology and can only be used by engineers when providing advice outside of earthquake-prone building system requirements.

Section C5 'Concrete Buildings' was updated by sector experts in 2018 to incorporate lessons from the Kaikoura Earthquake on how concrete buildings, particularly those with pre-cast hollow-core floors, perform in an earthquake. This update is informally known as the 'Yellow Chapter'.

In 2025, several sections of the Guidelines, including Section C5, are being updated to reflect the results of new research and industry input from the use of the Guidelines over the past eight years. 

Access the revised Section C5 - Concrete Buildings - design.resilience.nz

Section C5 purpose

Section C5 of the Non-Earthquake Prone Building Seismic Assessment Guidelines (Guidelines) provides engineers with guidance on how to conduct seismic assessments of concrete buildings outside the earthquake-prone building (EPB) system. The revised Section C5 is expected to improve the clarity, consistency and accuracy of these assessments, and supersedes the 2018 'Yellow Chapter'.

The revised Section C5 should be used to help facilitate a wider conversation with building owners around building performance. It should not be used to provide a %NBS rating in isolation.

The revised Section C5 does not replace the Red Book in the EPB legislation.

Guideline to follow depends on purpose of assessment

When carrying out seismic assessments of potential earthquake-prone buildings, engineers must use the Red Book. The assessment summary must contain the %NBS.

Going forward, if an assessment is being done for any purpose outside the EPB system, the revised sections of the Non-Earthquake Prone Building Seismic Assessment Guidelines can be used by engineers to support a discussion with building owners about the seismic performance of the building and any remediation options.

Review of seismic risk management

There are no immediate plans to update the mandatory guidance documents for potentially earthquake-prone building assessments. A broader review of the way seismic risk is  managed in existing buildings is currently underway. The review is being led by MBIE and is expected to be completed in 2025.

Any changes to the EPB system that may follow the review must also be identified and considered before proposals can be made about the way potentially earthquake-prone buildings should be assessed in future.

Concerns about a building

Territorial Authorities are responsible for identifying potentially earthquake-prone buildings and ensuring that the building’s owners are identifying and managing the risk appropriately.

However, if there are concerns about a building, talk to the building owner to understand if it's been identified by a Territorial Authority, or if the owner wants to do a more proactive assessment.

It is not a requirement for building owners who have undertaken an earthquake-prone building assessment as requested by a Territorial Authority to voluntarily carry out a further assessment.

Related information

Engineering Assessment Guidelines (the Red Book)

Building Design & Construction Resources - design.resilience.nz