The design and assessment of earthquake-prone and earthquake-risk buildings in New Zealand


Designing buildings and structures to withstand earthquakes in New Zealand


Download pdf here

Currently in New Zealand buildings are being assessed in accordance with The Building Act 2004 and an Initial Evaluation Procedure as set out in the New Zealand Society Earthquake Engineering report of 2006. The Initial Evaluation Procedure (IEP) is a qualitativemethod based upon the dates when the building was constructed and therefore the structural building codes at the time, together with the type of structure, the materials used, and its positioning within New Zealand and proximity to seismic fault lines. Unfortunately, the procedure is not definitive enough to be relied upon, and often scores buildings above or below their true performance rating, and is therefore indicative only.

The IEP measures performance of an existing structure’s resistance to earthquakes by comparing it in percentage terms to the resistance required if a new building of a similar structure were to be built on the same site. This is known as %NBS or New Building Standard. The New Zealand Society for Earthquake Engineering’s report of 2006 sets benchmark levels of performance for existing structures of 33% and 67%.Below 33% the building is considered as Earthquake Prone, between 33% and 67% it is considered an Earthquake Risk, and above 67% is deemed acceptable and does not require any further action

If the structure falls below either level the localauthority has the right under the Building Act to instruct the owner to prove the building is not Earthquake Prone, strengthen the building, or demolish the building. If the building is to be strengthened it is the local authority’s right to set the level required for compliance, either >33% or >67%. An IEP does not require a detailed analysis and hence the conclusions of the IEP may be incorrect, and the building may
subsequently be proven not to be Earthquake Prone or an Earthquake Risk.

Dependent upon the findings of the IEP, a Detailed Seismic Assessment (DSE) may be required to more accurately determine the building’s % NBS.
Dependent upon the building’s original construction, we often find the % NBS score to be quite inaccurate when carrying out Detailed Seismic Assessments.

The Building Act 2004 – Legislative Basis for the Earthquake Prone Building Policy. The sections of the Building Act that refer to earthquake-prone buildings (EPBs) are in subpart 6 of Part 2 of the Act.Section 122 and its associated regulations define an EPB. 

Sections 124 to 130 provide power for Territorial Authorities to act on EPBs and set out how this action is to be taken. Sections 131 and 132 require TAs to establish EPB policies and specify how the policies are to be established, what they are to include and when they are to be reviewed.


Structural Engineers NZ Ltd’s expertise in this fieldis as follows:

  • We have an experienced Chartered Professional Engineer (CPEng) who is able to carry out both IEP & DSE assessment of buildings, commercial & industrial, accurately and objectively.
  • We have experience of analysing structures using the most current and sophisticated analysis techniques.Our reports are written clearly and concisely, and contain an initial Executive Summary which will describe the building’s performance in plain English despite the remainder of the report often being highly technical.
  • We are experienced in peer-reviewing documentationprovided by other engineers, Territorial Authorities, and if necessary, we can provide a CPEng engineer experienced in attending Court as an Expert Witness.


Initial Evaluation Procedures

Our reports are presented in a clear and concise manner:

Seismic Analysis

They will contain all of the information required by the local Council (Territorial Authority).
They will give clear & concise advice on what to do next. This advice will take into account the owner’s legal responsibility, and
will break down costings for our services, often ina staged approach to ensure that these costs are kept to a minimum.
Generally, the cost of preparing such a report would be between $1000 – $2000, depending upon the size & complexity,and
location, of the building.
We cover the entire Central North Island, although we can travel to anywhere in New Zealand at your request.


We strongly believe in the strength of client liaison & relationships. We strive to achieve objective reports (which are legal documents) which provide clear, no-nonsense guidelines, and ateach step of the process we will discuss our findings with our clients in an open and transparent manner.

Client confidentiality is paramount to us.

Detailed Seismic Assessments

Our reports are presented in a clear and concise manner:

Seismic Analysis & Design 
Again, they will contain all of the information required by the local Council (Territorial Authority). Dependent upon the building owner’s instructions, they can contain details of strengthening procedures and indicative costs, to bring the building up to a certain %NBS. This can be 70%, 80% or even 100% NBS.

We use sophisticated analysis software combined with over 40 year’s experience in structural engineeringdesign of all types of commercial & residential buildings. Our clients can be assured of the best possible service, which is both technically and legally correct, and cost-effective.

We can arrange to visit you to discuss your requirements, program, costings etc. We have carried out work for all types of buildings, be they steel-framed, reinforced masonry, reinforced concrete, or timber. Often buildings are of hybrid construction (one or more of the above) and we specialise in these types of analyses.


For further information regarding SENZ’s capabilities, and how we can help you.

Please contact Ted Dowdall at
This email address is being protected from spambots. You need JavaScript enabled to view it.

or tel: 09 88 99 350.


Download pdf here

FacebookTwitterGoogle BookmarksLinkedinRSS Feed