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Section 3: Territorial authorities decide on earthquake-prone buildings

This section is for territorial authorities. It covers:

  • how to accept an engineering assessment
  • how to accept a previous assessment
  • how to decide if a building is earthquake prone, and
  • if so, how to decide the earthquake rating.

3.1 Scope for these decisions

This methodology sets out how a territorial authority is required to determine whether a potentially earthquake-prone building is earthquake prone and, if it is, its earthquake rating by specifying:

  1. in sections 3.2 and 3.3, criteria that must be met by an engineering assessment or a previous assessment for a territorial authority to accept the assessment, and
  2. in sections 3.4 and 3.5, how a territorial authority is to determine if the building is earthquake prone in accordance with section 133AB of the Building Act and, if it is, its earthquake rating.

If a territorial authority identifies a building as potentially earthquake prone in accordance with section 1.0 of this methodology, and

  1. the building has a previous assessment that was obtained by the territorial authority or provided by the owner prior to commencement, and
  2. the previous assessment meets the criteria set out in section 3.3 of this methodology,

before determining whether the building is earthquake prone or not, the territorial authority should notify the owner that the building is potentially earthquake prone and give the owner the option to either agree with and use the previous assessment (ie by relying on the previous assessment and the %NBS it provides), or obtain an engineering assessment in accordance with section 2.0 of this methodology.

If an engineering assessment or previous assessment is not accepted by the territorial authority, the territorial authority should advise the owner why it was not accepted.

If an owner has a previous assessment that does not meet the criteria set out in section 3.3 of this methodology, an owner may commission a suitably qualified engineer (as described in section 2.2 of this methodology) to revisit this previous assessment and address the missing criteria retrospectively. If the owner can provide supplementary evidence from a suitably qualified engineer that addresses the outstanding criteria, the territorial authority can accept the previous assessment.

Under section 133AK(4) of the Building Act, if the territorial authority does not receive an engineering assessment within the time frame required, or is notified that the owner does not intend to provide an engineering assessment within the time frame required, the territorial authority must proceed as if it had determined the building to be earthquake prone.

3.2 Criteria for accepting an engineering assessment

An engineering assessment must meet the requirements set out in section 2 of this methodology, including being reported in accordance with section 2.5 of this methodology.

The territorial authority must accept the engineering assessment if these requirements are met.

If the territorial authority has concerns about whether the engineering assessment meets the requirements set out in section 2 of this methodology, the territorial authority may request further substantiation from the owner.

3.3 Criteria for recognising a previous assessment

A previous assessment may be in the form of an Initial Evaluation Procedure, an Initial Seismic Assessment, a Detailed Engineering Evaluation, or a Detailed Seismic Assessment. It may be held on record by a territorial authority before commencement or provided by an owner any time after commencement.

A territorial authority may accept a previous assessment if either:

i. the previous assessment:

  • was undertaken by a suitably qualified engineer with relevant skills in structural and earthquake engineering and assessments of existing buildings. As a minimum requirement, the engineer is expected to be a structural engineer who is chartered under the Chartered Professional Engineers of New Zealand Act 2002, or equivalent (for example a Registered Engineer prior to 2002), and who held that status at the time the assessment was undertaken, and
  • contains evidence that an external and internal inspection was carried out as part of the assessment, or appropriate commentary where an internal inspection was not completed. Where no internal inspection has been carried out or appropriate commentary provided, the existing assessment report may be submitted with supplementary evidence from a suitably qualified engineer to confirm that an internal inspection has been completed retrospectively and the results of the previous assessment have not altered as a consequence of that inspection, and
  • references the relevant standard or guidelines for acceptable engineering methods in effect at the time, for example the Assessment and Improvement of the Structural Performance of Buildings in Earthquakes guidelines produced in June 2006 by the New Zealand Society for Earthquake Engineering, or a draft version of the Engineering Assessment Guidelines released for use in June or August 2016, and
  • clearly states the assessment outcome, reported as a %NBS, however

    if a territorial authority has concerns about whether the previous assessment meets the requirements set out above, the territorial authority may request further substantiation from the owner

or,

ii. there is evidence that the previous assessment has undergone an independent review by a Chartered Professional Engineer 

or,

iii. the previous assessment was undertaken as part of a programme of assessments (by either the territorial authority or the owner) that was subject to a moderation process with appropriate technical input and programme oversight from a suitably qualified engineer or engineers with relevant skills in structural and earthquake engineering and in assessments of existing buildings.

3.4 Determining if a building is earthquake prone

If a territorial authority accepts an engineering assessment in accordance with the criteria in section 3.2 of this methodology or a previous assessment in accordance with section 3.3 of this methodology, the territorial authority must determine whether or not the building is earthquake prone in accordance with sections 133AB and 133AK of the Building Act.

3.4.1 Section 133AB(1)(a)

Section 133AB(1)(a) of the Building Act is met if the assessment of the ultimate capacity of the building and its parts, and the relationship of this to moderate earthquake shaking, is less than 34%NBS, ie the %NBS in the engineering assessment report.

3.4.2 Section 133AB(1)(b)

Section 133AB(1)(b) of the Building Act is met if:

  1. access to the building is not likely to be difficult, limited or infrequent; and that access is to an area affected by the mode of failure and physical consequence identified in the engineering assessment report, or
  2. the mode of failure and physical consequence identified in the engineering assessment report would be likely to cause damage to other property, or 
  3. there is another reason why the collapse of the building or failure of the elements identified in the engineering assessment report would be likely to cause injury or death to a number of persons in or near the building, or damage to other property.

This decision should be informed by consideration of the following information:

  1. the current and possible occupancy of the building
  2. the possible accessibility to the building, or site of the building; ie whether people can approach or enter the building
  3. if there are any neighbouring buildings and the proximity of these, and
  4. the mode of failure and physical consequence of the building identified in the engineering assessment report.

3.5 Determining the earthquake rating

If a territorial authority determines a building is earthquake prone in accordance with section 3.4 of this methodology, the territorial authority must assign an earthquake rating.

The earthquake rating of the building will be the %NBS specified in the engineering assessment report. The earthquake rating will correspond with an earthquake rating category prescribed in the Building (Specified Systems, Change the Use, and Earthquake-prone Buildings) Regulations 2005.

That earthquake rating category will determine the form of EPB notice that is to be issued.

This information is published by the Ministry of Business, Innovation and Employment’s Chief Executive. It is a general guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case. Expert advice may be required in specific circumstances. Where this information relates to assisting people: