Section 1: Territorial authorities identify potentially earthquake-prone buildings
This section is for territorial authorities. It covers:
- what the profile categories are and how to use them to identify potentially earthquake-prone buildings
- how to identify other buildings as potentially earthquake prone at any time.
1.1 Scope for identifying these buildings
This methodology sets out how a territorial authority must identify potentially earthquake-prone buildings.
The territorial authority:
- must identify potentially earthquake-prone buildings that fall within the categories of buildings, known as profile categories, specified in section 1.2 of this methodology within the time frames specified in section 133AG(4) of the Building Act
- may identify a building as potentially earthquake prone at any time under section 133AG(3) of the Building Act if it has reason to suspect the building may be earthquake prone. Reasons that may cause a territorial authority to suspect a building may be earthquake prone are set out in section 1.3 of this methodology.
The territorial authority must notify the owner and request an engineering assessment in accordance with section 133AH of the Building Act.
Before applying the profile categories to identify potentially earthquake-prone buildings, a territorial authority should consider: how it has identified earthquake-prone buildings prior to commencement of the Building Act; whether buildings in one or more of the applicable profile categories have previously been identified as potentially earthquake prone or earthquake prone; and the information held about these buildings, eg a previous assessment.
Parts of buildings are only required to be considered in accordance with the scope of parts set out in section 2.4.1 of this methodology when an engineering assessment is required, ie when a building is not identified as potentially earthquake prone (and therefore an engineering assessment is not required), individual parts of buildings are not expected to be identified.
A building that is out of scope as defined in section 133AA of the Building Act cannot be identified as potentially earthquake prone or determined earthquake prone; ie most residential housing, farm buildings, retaining walls that are not integral to the structure of a building, fences, certain monuments, wharves, bridges, tunnels and storage tanks.
1.2 How to identify using profile categories
A territorial authority must identify buildings in its district that are within the following profile categories as potentially earthquake prone within the applicable time frames set out in section 133AG(4) of the Building Act.
1.2.1 Categories of buildings for the different seismic zones
The following profile categories apply:
| High seismic risk areas and medium seismic risk areas | Low seismic risk areas | |
|---|---|---|
| Category A | Unreinforced masonry buildings | Unreinforced masonry buildings |
| Category B | Pre-1976 buildings that are either three or more storeys or 12 metres or greater in height above the lowest ground level (other than unreinforced masonry buildings in Category A) | Pre-1976 buildings that are either three or more storeys or 12 metres or greater in height above the lowest ground level (other than unreinforced masonry buildings in Category A) |
| Category C | Pre-1935 buildings that are one or two storeys (other than unreinforced masonry buildings in Category A) |
1.2.2 Exclusions
The following buildings are excluded from the profile categories:
- a building that is constructed primarily of timber framing without other construction materials providing lateral support
- a building strengthened to at least 34%NBS (or the equivalent of this) so that the building cannot be considered earthquake prone
- a building that a territorial authority has previously notified the owner in writing is not earthquake prone prior to commencement
- a building that the territorial authority has found to be earthquake prone and for which it has issued a notice under section 124 of the Building Act prior to commencement (and is therefore subject to Schedule 1AA of the Building Act)
- a building for which the territorial authority has a previous assessment that has a %NBS reported for the building greater than 34%NBS and that meets the criteria set out in section 3.3 of this methodology
- buildings for which a territorial authority obtains information or a special study that shows a particular subset of buildings is not earthquake prone due to particular circumstances or special local characteristics, where there is a robust technical basis for this information or study.
1.2.3 Category details
Category A
Unreinforced masonry buildings.
This includes:
- strengthened unreinforced masonry buildings, unless there is evidence that the strengthening has achieved at least 34%NBS (or the equivalent of this)
- a building of any construction type with a significant original unreinforced masonry section or part.
Description and streetscape building characteristics
Buildings originally constructed of masonry (brick, block, or stone) without any apparent form of reinforcement or independent lateral support. Streetscape building characteristics are:
- solid brick or stone facades, with or without openings
- buildings of unreinforced masonry bearing wall construction (and including buildings of any construction with unreinforced masonry parapets that are not obviously concrete or other forms of construction)
- masonry walls that do not feature concrete column and beam elements
- solid masonry gable end walls
- brick chimneys.
Examples
Smaller commercial and industrial buildings, larger retail and hotel buildings, and buildings with complex features, eg churches.
Category B
Pre-1976 buildings that are either three or more storeys or 12 metres or greater in height (other than unreinforced masonry buildings in Category A).
Description and streetscape building characteristics
Buildings of heavy construction that are either three or more storeys or 12 metres or greater in height, and designed prior to 1976, and not constructed substantially of unreinforced masonry or timber framing. Most buildings within this category are likely to be of concrete or concrete encased steel construction, or of reinforced concrete masonry.
Streetscape building characteristics are listed in an indicative priority order to assist with prioritisation for identification due to the number of buildings in this category. Streetscape building characteristics are:
- buildings of five or more storeys
- buildings of three or more storeys on corner sites
- all other buildings of three or four storeys
- buildings of one or two storeys and 12 metres or greater in height.
Examples
Commercial buildings including office, retail, hotel, and educational buildings.
Hotels with an open lobby and retail arcades with an open ground floor (compared to upper floors).
Churches, auditoria and cinemas (one or two storeys and 12 metres or greater in height).
Category C
Pre-1935 buildings that are one or two storeys (other than unreinforced masonry buildings in Category A).
Description and streetscape building characteristics
Buildings that are one or two storeys, and constructed before 1935, and not constructed substantially of unreinforced masonry or timber framing.
Most buildings are likely to be of concrete construction or concrete encased steel framing.
Streetscape building characteristics include facades and walls that feature concrete column and beam elements and concrete suspended floors.
Examples
Commercial buildings including office, retail, hotel and educational buildings.
1.2.4 How to apply the categories
The following provides further explanation about the application of the profile categories:
- The dates specified in the profile categories reflect the design dates of buildings and are applicable to the earliest designed section of the building, not subsequent work or additions to the structure. Design dates should be established based on existing records including drawings and calculations, approvals, permits and building consent dates, or could be inferred from other building information.
- The building heights specified in the profile categories are to be taken from the lowest ground level surrounding the building to the highest point on the roof structure.
- Plans, drawings or other existing records and a visual inspection are considered acceptable evidence to identify buildings that correspond with the profile categories. The visual inspection should confirm details.
1.3 How to identify at any time
A territorial authority may identify a building as potentially earthquake prone at any time under section 133AG(3) of the Building Act, if a territorial authority has reason to suspect the building may be earthquake prone.
Reasons that may cause a territorial authority to suspect a building may be earthquake prone include:
- if a territorial authority receives an assessment or other material (whether undertaken for the purposes of considering whether a building could be earthquake prone or for any other purpose) that contains information about a building’s seismic performance and that indicates the building may be earthquake prone
- if a territorial authority becomes aware of issues (by way of information provided to the territorial authority or other means) that could affect or impact on a building’s seismic performance at moderate levels of earthquake shaking, such as:
- particular construction types, where the construction type is not included in the profile categories but is expected to contain some earthquake-prone buildings (eg a timber frame building of two or more storeys on a significant slope), or
- complex design or construction with known conditions that require further engineering analysis. This could include a building with non-ductile columns, a building with no effective connection between primary seismic structural elements and diaphragms, or a building with seismically separated stairs with ledge and gap supports, or
- ground conditions that could lead to a significant loss of support for a structure.