Did you know that Upper Hutt has a policy on earthquake prone buildings?
Read on to learn more about this policy, how it may affect you and the steps your council is undertaking to make your city a safer place to live and work.
Upper Hutt City lies in a medium to high seismicity zone, with a number of significant active faults, including the Wellington fault, Akatarawa fault, Otaki Forks fault, Moonshine fault and Whitemans Valley fault, all of which are large and close enough to potentially cause significant damage to the city.
Upper Hutt City Council is committed to ensuring that your city is a safe place to live and work. This includes making sure that buildings comply with the Building Act 2004.
The Building Act imposes earthquake standards for commercial properties and requires councils across New Zealand to develop an earthquake prone buildings policy.
Upper Hutt City Council adopted the ‘Earthquake Prone, Dangerous and Insanitary Building Policy’ in March 2006. Read more on the Council’s Earthquake Prone Building Policy on page 153 of the Manual of Policies.
The Council’s Earthquake Prone Buildings Policy outlines how earthquake-prone buildings are identified and the time frames property owners are given to either strengthen or demolish the building.
Since the Policy was adopted, the Council’s building services team have been working behind the scenes to review buildings affected. The following frequently asked questions best describe the work we are doing in implementation of the Policy.
Read more on the Council’s Earthquake Prone Building Policy in the Manual of Policies (page 128 – section 5.3)
Frequently asked questions for building owners in Upper Hutt
Q What is an earthquake prone building?
A This is a building that has less than one third (33%) of the seismic (earthquake) bracing strength that would be required for a new building designed to current codes.
Q Where does the term earthquake prone building come from?
A This term is used in Building Act 2004 as a way to describe a building that is considered unacceptably unsafe in an earthquake.
“A building is earthquake prone for the purposes of this Act if, having regard to its condition and to the ground on which it is built, and because of its construction, the building –
- will have its ultimate capacity exceeded in a moderate earthquake (as defined in the regulations): and
- would be likely to collapse causing –
- injury or death to persons in the building or to persons on any other property; or
- damage to any other person.” – Building Act 2004 clause 122
This legislation is driven by central government but requires local councils to develop an earthquake prone building policy and to enforce this policy.
Q How do I know if my home is affected by this policy?
A All residential buildings built after 1976 are excluded. Pre-1976 residential buildings are also excluded unless they are:
- registered with the New Zealand Historic Places Trust; or
- two storeys or more and contain three or more households
Q How do I know if my building is affected by this policy?
A Buildings built after 1976 are not required to be assessed.Council will assess pre-1976 buildings and only notify you if the assessment shows work is required to bring your building into compliance.The assessment results will also be placed on the building file for your building and included in LIMs and PIMs.
Q Why has the level of one third been selected?
A Below this level the possibility of catastrophic failure (i.e. total collapse of the building) during a significant earthquake was considered too high. During an earthquake a building that is not designed to the New Zealand Standards level will sustain more damage than a building designed to the code. The amount of damage to the building, and the risk of injury or loss of life, increases as the building strength reduces.Statistical research, partly based on damage to buildings in overseas earthquakes, has found that the chance of loss of life or serious injury is more than 10 times higher in an earthquake prone building that in a building designed to the New Zealand Standards level (refer to the NZSEE table below). For more information on the Grading system for earthquake risk, please refer to the NZSEE document ‘Assessment and Improvement of the Structural Performance of Building in Earthquake‘ on the New Zealand Society for Earthquake Engineering website.
Q How does the Council identify potentially earthquake prone buildings?
A The Upper Hutt City Council firstly completed a desk top study to screen their building stock to identify buildings that are potentially earthquake prone and that should be assessed further. Having identified these buildings Upper Hutt City Council has completed what is called an Initial Evaluation Process (IEP) assessment for each building to confirm if it is potentially earthquake prone. If they believe a building is earthquake prone the Council have notified the building owner.
Q What is an IEP assessment?
A The Initial Evaluation Process (IEP) assessment method is a quick method of identifying if a building is potentially earthquake prone. This assessment method has been developed by the New Zealand Society of Earthquake Engineers (NZSEE). This method takes into account a number of factors such as;
- building age (the code the building was designed to)
- construction type (timber, concrete, steel, brick etc)
- building form (no. storeys, storey height, location of bracing elements)
- proximity to neighbouring building.
Using this information the IEP derives an indicative percentage New Building Standard (%NBS) “score”. The %NBS is an indication of the capacity of the building compared to the required strength for a new building designed to current New Zealand Standards.
The IEP assessment method is not as accurate as a detailed assessment and is intended as a cost effective method of indicating if a building is potentially earthquake prone. If the score is greater than 33%NBS then the building is accepted by most district councils as not earthquake prone and further assessment is not required.
Some points to note about the IEP assessment method
- The more information that is used the more accurate the IEP assessment will be
- The IEP assessment should involve an external and internal inspection of the building
- If a building has previously been strengthened account of this should be taken in the IEP assessment
- The IEP assessment should be carried out by an experienced structural engineer.
Q What is the earthquake prone building’s register?
A This is a record kept by Council of buildings that are considered to be earthquake prone. This information is available to the public and will be disclosed on LIMs. For enquiries about or access to the earthquake prone building’s register please contact the Building Control Team at the Council on (04) 527 2169 or email us
Q How do I get my building off the register?
A Prove your building is not earthquake prone. This can be done using following methods:
- Challenge the Council IEP.
- Carry out a detailed seismic assessment (only required if the building fails the IEP assessment)
- Strengthen or demolish your building (only required if a detailed assessment finds your building is earthquake prone).Q
Q How do I challenge the IEP Assessment?
A This can be assessed using the following methods;
- Refer to structural calculations (if these are available) to see the level the building was designed to.
- Carry out an independent IEP assessment.
If the original calculations are available this may show the level the building was designed to. For buildings constructed more recently these calculations may be found in the Council Archives or you may have records of these. The older the building the harder it is to find the original calculations. In most cases buildings that were designed post 1976 to the 1976 Loadings Standard (NZS4203:1976) are not earthquake prone.
Q What if the findings of Council IEP are correct?
A If the IEP assessment has identified that a building is potentially earthquake prone this does not mean that the building is earthquake prone. The IEP assessment method is really only a screening process to indicate potentially earthquake prone buildings. The next step is to carry out a detailed assessment that will accurately calculate the earthquake capacity of the building. If the detailed assessment finds that your building has less than 34% of the required code strength then your building is earthquake prone. Your building will need to be either strengthened or demolished in order to be removed it from the Earthquake Prone Building Register.
Q I had my building strengthened a few years back. Surely I don’t have to do this again?
A Unfortunately you might. Up until the last few years it was only necessary to strengthen buildings to two thirds the level required in the 1965 loadings standard. This level is a fraction of the strength required in current standards. If your building was previously strengthened to the minimum level required there is a chance you will need to strengthen you building again. In some cases the engineer involved in the strengthening may have advised strengthening to a higher level. If this is the case your building may be closer to the strength required in today’s standards and a review of available calculations may show this without the need for a detailed seismic assessment.This is a record kept by Council of buildings that are considered to be potentially earthquake prone. This information is available to the public and will be disclosed on LIMs.
Last updated on 24 Aug 2016