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.

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.

C3.5C3.7
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 to C/AS7
The Acceptable Solutions (C/AS2 to C/AS7) contain three means of demonstrating compliance:
  • Fire properties of external wall cladding systems must be in accordance with ISO 5660 Reaction-to-fire tests – Heat release, smoke production and mass loss rate – Part 1: Heat release rate (cone calorimeter method), or
  • External wall cladding systems must comprise only materials that individually are classified as non-combustible (exempting a 1 mm combustible finish), or
  • The entire wall assembly must be tested at full scale in accordance with NFPA 285 and must pass the test criteria.
Compliance Pathway – Verification Method C/VM2
The Verification Method (C/VM2) contains four means of demonstrating compliance:
  • Fire properties of external wall cladding systems must be in accordance with ISO 5660.1 or AS/NZS 3837, as per the tables in C/VM2, or
  • The external wall cladding system must use non-combustible materials, or
  • The external wall cladding system must comply with the Acceptable Solutions (for buildings with an importance level not higher than 3).
  • Large or medium scale
    facade type tests must be
    used to determine the
    extent of vertical fire spread
    is not more than 3.5 m above
    the fire source (C3.5)
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.

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: