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New Zealand Building Code compliance pathways

Summarises available compliance pathways for Building Code Clause C3 External spread of fire.

The Building Code is performance based. Clause C of the Building Code describes the performance criteria for Protection from Fire. Clause C3 describes Functional and Performance Requirements for fire affecting areas beyond the fire source.

Functional Requirements – Building Code Clause C3

  • C3.1 Buildings must be designed and constructed so that there is a low probability of injury or illness to persons not in close proximity to a fire source.
  • C3.2 Buildings with a building height greater than 10 m where upper floors contain sleeping uses or other property must be designed and constructed so that there is a low probability of external vertical fire spread to upper floors in the building.
  • C3.3 Buildings must be designed and constructed so that there is a low probability of fire spread to other property vertically or horizontally across a relevant boundary.

There are two Performance Clauses that describe the constraints for control of external vertical fire spread:

  • Clause C3.5 – limiting the vertical spread of fire
  • Clause C3.7 – covering the ignitability of external wall cladding materials.

Consideration need to be given to Clause C3.9 which relates to the likelihood and consequence of failure of fire safety systems.

Three pathways are available to demonstrate compliance with the Building Code Performance Requirements: Acceptable Solutions, Verification Methods and alternative solutions.

Note: CodeMark and Multiproof are alternative means for demonstrating compliance with the Building Code.

The following table outlines the Performance Requirements of the New Zealand Building Code and summarises the associated compliance pathways:

Compliance Pathways for New Zealand Building Code Clause C3 - External Spread of Fire.

C3.5 Limiting vertical fire spread C3.7 Covering the ignitability of external wall cladding materials
Building Code Performance Requirements
Buildings must be designed and constructed so that fire does not spread more than 3.5 m vertically from the fire source over the external cladding of multi-level buildings. External walls of buildings that are located closer than 1 m to the relevant boundary of the property on which the building stands must either:
  • be constructed from materials which are not combustible building material, or
  • for buildings in importance levels 3 and 4, be constructed from materials that, when subjected to a radiant flux of 30 kW/ m2, do not ignite for 30 minutes, or
  • for buildings in importance levels 1 and 2, be constructed from materials that, when subjected to a radiant flux of 30 kW/ m2, do not ignite for 15 minutes.
Compliance Pathway – Acceptable Solutions C/AS2 and Verification C/VM2

The compliance pathway is split for buildings over 10 m in height and those over 25 m in height.

For buildings over 10 m in height and less than 25 m in height, cladding materials must:

  1. Be non-combustible or limited combustible materials, or
  2. Be tested in accordance with ISO 5660 Part 1 or AS/NZS 3837 and achieve the relevant performance classifications, or
  3. Be part of an external wall cladding system that complies with the large scale or intermediate scale fire testing options described below for buildings above 25 m.

For buildings over 25 m in height, the entire external wall cladding system is required to:

  1. Be comprised of non-combustible or limited combustible materials, or
  2. Undergo large scale fire testing in accordance to BS 8414-1 or BS 8414-2 and achieve the relevant performance criteria specified in AS 5113 or BR 135, or
  3. Undergo intermediate scale fire testing in accordance to NFPA 285 and additionally be comprised of cladding materials that are
    1. non-combustible or limited combustible materials; or
    2. tested in accordance with ISO 5660 Part 1 or AS/NZS 3837 and achieve the relevant performance classification.

Note: for buildings with importance level 4, C/VM2 does not permit the small scale testing options of cladding materials described for buildings > 10 m in height and assessment as an entire external wall cladding system is required.

Where walls are located within 1m from the relevant boundary, the compliance pathway contains two means to demonstrate compliance for cladding materials:

  1. Be non-combustible or limited combustible materials, or
  2. Be tested in accordance with ISO 5660 Part 1 or AS/NZS 3837 and achieve the relevant performance classifications.
Compliance Pathway – Alternative Solution
An alternative solution proposal must be provided that justifies how the design of the building will not result in fire spread of more than 3.5 m vertically from the fire source over the external cladding of multi-level buildings.
  1. The external wall cladding system must use non-combustible materials (combustible building materials is a defined term in the Building Regulations, and “means" building materials that are deemed combustible according to AS 1530.1), or

    An alternative solution proposal must be provided that justifies how either:
  2. for buildings in importance levels 3 and 4, the external wall cladding system is constructed from materials that, when subjected to a radiant flux of 30 kW/ m2, do not ignite for 30 minutes, or
  3. for buildings in importance levels 1 and 2, the external wall cladding system is constructed from materials that, when subjected to a radiant flux of 30 kW/ m2, do not ignite for 15 minutes.
The above criteria for b and c can be achieved by the use of bench scale fire tests (e.g. ISO 5660-1) to confirm that materials when exposed to 30 kW/ m2 do not ignite within the specified time period.
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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: