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Category 1 buildings

In summary, a Category 1 building is a detached or semi-detached residential dwelling of conventional timber-frame or masonry construction, and low- or medium risk envelope design.

A Category 1 building must meet all of the following criteria:

Structure

  • must be straightforward/conventional construction designed in accordance with NZS 3604:1999 Timber Framed Buildings and/or NZS 4229:1999 Concrete Masonry Buildings Not Requiring Specific Design, but can have:
    • engineer-designed or proprietary foundations, lintels and roof structures (eg roof trusses)
    • specifically designed structures such as conservatories, porches and pergolas.

Use

  • must be a residential dwelling
  • must be detached (SH use see glossary), or semi-detached (SR use see glossary) to a maximum of two side-by-side units:
    • An SH building has no prescribed occupant limits
    • A semi-detached building (ie SR) technically has an occupant limit per floor of 50 people. However, in practice, occupant numbers are unlikely to be an issue since even large dwellings do not normally house this many people
  • must be importance level 2 (normal) based on AS/NZS 1170.0 (see glossary).

Risk score

  • must be a low- or medium-risk envelope design with a risk score not exceeding 12 for any external face, based on the E2/AS1 risk matrix (see glossary).

Status

  • cannot be a registered historic place under the Historic Places Act 1993 (see glossary).

Note:

Cross.   A building with three or more side-by-side household units cannot be classified as Category 1.
Cross.  A building with one household unit above another cannot be classified as Category 1.
Cross.  Steel-framed houses cannot be classified as Category 1.

Examples: Category 1 buildings

Example 1.1: Simple single-storey house

Example 1.1: Simple single-story house.

Structure

The building is within Category 1 limits:

  • The structure is generally designed to NZS 3604
  • It is assumed that roof trusses based on a proprietary design package have been used
  • It is assumed that part of the foundation is supported by a specifically designed pile.

Use

The building is within Category 1 limits:

  • It is a detached dwelling (SH see glossary)
  • Occupant limits do not apply
  • The house is a normal building.

Risk score

  • The building has a risk matrix score based on E2/AS1 of 0 on all elevations based on:
    • Medium wind zone (assumed)
    • Single storey
    • Low-risk roof/wall intersections and 600 mm eaves
    • Simple design with brick veneer cladding
    • Low-risk deck.
      (Category 1 allows a maximum of 12 on any face.)

Status

The building is not a registered historic place.

Therefore it is a Category 1 building.

Example 1.2: Semi-detached residential units

Example 1.2: Semi-detached residential units.

Structure

The building is within Category 1 limits:

  • The structure is generally designed to NZS 3604
  • It is assumed that roof trusses based on a proprietary design package have been used.

Use

The building is within Category 1 limits:

  • It comprises two semi-detached dwellings (SR)
  • Occupant limits do not apply
  • It is a normal building. 

Risk score

The building has a risk matrix score based on E2/AS1 of 10 on the highest risk elevation (north), based on:

  • Very high wind zone (assumed)
  • Two storeys
  • Low-risk roof/wall intersections
  • 450 mm eaves (excluding spouting)
  • Simple design but has two claddings (EIFS and horizontal corrugated iron)
  • High-risk cantilevered decks.
    (Category 1 allows a maximum of 12 on any face.)

Status

The house is not a registered historic place.

Therefore it is a Category 1 building.

Example 1.3: Two-storey house

Example 1.3: Two-storey house.

Structure

The building is within Category 1 limits:

  • The structure is generally designed to NZS 3604
  • Roof trusses based on a proprietary design package have been used
  • Some proprietary lintels and a specific design lintel over the garage have been used
  • Part of the foundation is supported by a specifically designed pile.

Note: If the house design included engineered floor joists, or other engineer input such as portal frames or specific bracing design, it would not qualify as a Category 1 building.

Use

The house is within Category 1 limits:

  • The house is a detached dwelling (SH)
  • Occupant limits do not apply
  • The house is a normal building.

Risk score

The house has a risk matrix score based on E2/AS1 of 11 on the elevation shown, based on:

  • Very high wind zone (assumed)
  • Two storeys
  • Low-risk roof/wall intersections
  • 450 mm eaves
  • Simple design but has two claddings (EIFS and weatherboard)
  • High-risk enclosed deck.
    (Category 1 allows a maximum of 12 on any face.)

Status

The house is not a registered historic place.

Therefore it is a Category 1 building.