Building categories

The scheme uses 3 building categories to identify how applicants should be assessed and to provide a scope for the licence classes.

The new building categories are complexity based, ranging from simple low risk dwellings in category 1 to complex multi-storey commercial in category 3. The definition excludes ancillary and outbuildings.

Building categories

Building categoryDefinitionDescription
Category 1 buildings 1. SH use and
2. risk score of 12 or less for any external elevation
Single household dwellings with low-or medium-risk envelope design.
Category 2 buildings 1. SH use and
2. risk score greater than 12 for any external elevation.
OR
1. not SH use, and
2.building height less than 10m.
Single household dwellings with high-risk envelope design, or buildings with a building height* less than 10m.
Category 3 buildings 1. not SH use, and building height greater than 10m All buildings 10m or greater in building height*, except single household dwellings.
VariableDefinition
Use (SH or other)

SH means sleeping single home.

SH use includes detached dwellings where people live as a single household or family, including attached self-contained spaces such as granny flats when occupied by a member of the same family.

Risk score

Risk score is based on the E2/AS1 risk matrix, which scores risk according to a building:

  • wind zone
  • number of storeys
  • roof/wall intersections
  • eaves width
  • envelope complexity
  • deck designs
Building height Building height means the vertical distance between the upper surfaces of the floors of the buildings lowest and highest storeys.

Is the building SH use?

You can ask just three questions about a building to determine its category:

  • Yes - Is the Risk score 12 or under? - Yes - Category 1
  • Yes - Is the Risk score 12 or under? - No - Category 2
  • No - Is the Building height less than 10m? - Yes - Category 2
  • No - Is the Building height less than 10m? - No - Category 3

Category 1

Category 1 buildings are single household dwellings with low- or medium-risk envelope design.

Specifically:

  • SH use, and
  • risk score of 12 or less for any external elevation.

Example 1

Single household dwelling

Use: The house is a single household dwelling (SH)

Risk score: The house has a risk matrix score of 0 based on E2/AS1 on all elevations shown, based on:

  • medium wind zone (assumed)
  • single storey
  • low-risk roof/wall intersections
  • 600mm eaves
  • simple design with brick veneer claddings
  • low-risk deck.

A Category 1 building is defined as SH use, with a maximum of 12 risk score on any elevation. Therefore, this building is Category 1.

Category 2

Category 2 buildings are single household dwellings with high-risk envelope design, or other buildings with a building height of 10m or less.

Specifically:

  • SH use, and
  • risk score greater than 12 for any external elevation.

or

  • not SH use, and
  • building height less than 10m.

Example 2

Elevation risk score house

Use: The house is a single household dwelling – SH use.

Risk score: The house has elevation risk scores greater than 12, based on E2/AS1 factors:

  • high wind zone (assumed)
  • 2 storeys
  • high-risk roof/wall intersections
  • 600mm eaves, but at two storeys this is a medium risk
  • high or very high envelope complexity depending on the elevation
  • high-risk roof decks.

This building is SH use, so it cannot be a Category 3. It has a risk score greater than 12, so it cannot be Category 1. Therefore, it must be Category 2.

Example 3

Commercial building

This is a four-storey, mixed-use commercial building with a building height of 9.6m.

The building’s use is not SH, so it could be Category 2 or 3, but the building height is less than 10m, therefore, it is a Category 2 building.

Category 3

Category 3 buildings are buildings 10m or greater in building height, except single household dwellings.

Specifically:

  • not SH use, and
  • building height 10m or greater.

Example 4

Five story apartment

This is a five-storey apartment building (SR use). It sits between two ground levels. The height from the floor level of the highest storey to the upper ground level is 6m, and 12m to the lowest ground level.

Use: The building is not SH use because it is not a single household dwelling.

Height: The building height is 12m.

A Category 3 building is defined as not SH use, where the building height is greater than 10m. Therefore, this is a Category 3 building.

Total risk score

A total risk score for an external elevation on the building envelope of a building is calculated by using the calculation and definitions of risk table below.

ElevationRisk severity   Subtotal
Risk factor Low Medium High Very high  
Wind zone 0 0 1 2  
Number of storeys 0 1 2 4  
Roof/elevation intersection design 0 1 3 5  
Eaves width 0 1 2 5  
Envelope complexity 0 1 3 6  
Deck design 0 2 4 6  
Total risk score  

Definition of risk table (E2/AS1)

Wind zone

Low risk Low wind zone as described by NZS 3604:1999
Medium risk Medium wind zone as described by NZS 3604:1999
High risk High wind zone as described by NZS 3604:1999
Very high risk Very high wind zone as described by NZS 3604:1999

Number of storeys

Low risk One storey
Medium risk Two storeys part
High risk Two storeys
Very high risk More than 2 storeys

Roof/elevation intersection design

Low risk Roof-to-elevation intersection fully protected (eg. hip and gable roof with eaves)
Medium risk Roof-to-elevation intersection partly exposed (eg. hip and gable roof with no eaves)
High risk Roof-to-elevation intersection fully exposed (eg. parapets, enclosed balustrades, or eaves at > 90° to vertical with soffit lining)
Very high risk Roof elements finishing within the boundaries formed by the external elevations (eg, lower ends of aprons, chimneys, dormers)

Eaves width

Low risk >600mm for single storey
Medium risk 451-600mm for single storey, or >600mm for 2 storey
High risk 101–450 mm for single storey, or 451–600 mm for 2 storey, or > 600 mm above 2 storey
Very high risk 0–100 mm for single storey, or 0–450 mm for 2 storey, or 600 mm or less above 2 Storey

Envelope complexity

Low risk Simple rectangular, L, T, or boomerang shape, with single cladding type
Medium risk Moderately complex, angular, or curved shapes (eg, Y or arrowhead) with no more than 2 cladding types
High risk Complex, angular, or curved shapes (eg, Y or arrowhead) with multiple cladding types
Very high risk As for high risk, but with junctions not covered in the rows of this table about roof/elevation intersection design and deck design (eg, box windows, pergolas, or multi-storey re-entrant shapes)

Deck design

Low risk None, timber slat deck or porch at ground-floor level
Medium risk Fully covered in plan by roof, or timber slat deck attached at first- or second-floor level
High risk Enclosed deck exposed in plan or cantilevered at first-floor level
Very high risk Enclosed deck exposed in plan or cantilevered at second- floor level or above