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Category 2 buildings

In summary, a Category 2 building is a building of moderate complexity, either commercial or less-conventional residential, with the highest occupied floor less than 10 metres above the exit (typically up to 3 floors) and limited occupant numbers.

A Category 2 building must meet the following criteria:

Structure/Risk

  • Has no limits on structure or envelope
  • Must have no occupied floors more than 10m above the exit.

Status

  • Cannot have a Historic Places Act category 1 rating.

Use

  • Cannot have uses that are high risk eg chemical manufacturing or processing plants, spray painting operations, bulk storage warehouses for flammable liquids or gases (WH or WF uses see glossary)
  • Cannot have a use that involves care and detention of people such as hospitals, care facilities for the aged, children or people with disabilities, detention quarters, or prisons (SC or SD uses see glossary)
  • Must have an importance level of 2 as defined in Table 3.2 of AS/NZS 1170.0 (see the glossary for a definition of importance levels)
  • Cannot have more people than listed in the table below:
Table indicating numbers of people allowed per floor in a Category 2 building
  Floor level
Ground Floor 1st Floor
(less than 4m above exit)		 2nd and 3rd floors 4m to < 10m above exit
Use People sleeping  up to 50  up to 25  up to 25
People working  up to 500  up to 250  up to 100
People in crowds
(eg shop, restaurant, school, theatre, stadium)		  up to 500  up to 250  0
Total number of people allowed  500  250  100

Examples: Category 2 buildings

Example 2.1: Residential building

Example 2.1: Residential building.

This example is based on the Department of Building and Housing publication External Moisture - A Guide to Using the Risk Matrix.

Structure

The structure is not within Category 1 limits, therefore it is Category 2:

  • The structure is generally designed to NZS 3604 (see quick reference guide) and
  • Roof trusses based on a proprietary design package have been used,
    but
  • Engineered mid-floor joists and portal frames have been used. These elements fall outside the scope of NZS 3604 and the allowable exceptions.

Use

  • A house can be either in Category 1 or in Category 2
  • The house is a detached dwelling (SH). Occupant limits and escape heights do not apply to SH.

Risk score

The house has elevation risk scores based on E2/AS1 that exceed the Category 1 maximum score of 12:

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

Status

  • The house is not a registered historic place.

This house exceeds the Category 1 limits for structure and risk score.

Therefore it is a Category 2 building.

Example 2.2: Mixed-use commercial/residential building

Example 2.2: Mixed-use commercial/residential building.

This is a four-storey, mixed-use commercial and residential building with the highest occupied floor 9.6 metres above the exit.

Structure/Risk

  • The building is clearly not within Category 1 limits because it is not totally a residential dwelling and it is outside the scope of NZS 3604/NZS 4229 (see glossary). There are no structure or envelope limits on Category 2 and Category 3 buildings.

Use

  • The CL, CM and SR (see glossary) uses are allowed in both Category 2 and Category 3. However, use alone does not determine the category.
    • Ground floor retail use (CM): 30 occupants
    • Ground floor restaurant use (CL): 90 occupants
    • First floor apartment use (SR): 2 apartments with 6 people in each
    • Second floor apartment use (SR): 2 apartments with 6 people in each
    • Third floor apartment use (SR): 2 apartments with 6 people in each
  • Occupant numbers: The highest occupied floor is less than 10m above the exit, and the occupant numbers are within the allowable limits, so the building is Category 2
Table indicating occupant numbers and limits for category 2 buildings
Storey Use Escape height Occupant numbers Occupant limits Category 2?
Ground  Retail (CM)  0  30  500  Tick.
 Restaurant (CL)  90
1  Apartment (SR)  3.6  12  25  Tick.
2  Apartment (SR)  6.6  12  25  Tick.
3  Apartment (SR)  9.6  12  25  Tick.
  • Importance level is 2 (normal structure). This could be category 2 or Category 3.

Status

  • The building is not a registered historic place.

The building has allowable uses and is within the height and occupant number limits for Category 2, and it is not a category 1 historic place.

Therefore it is a Category 2 building.