Protection from Fire: NZ Building Code Clause C

What is the NZ fire code?

The objectives of clauses C2 to C6 are to safeguard people from an unacceptable risk of injury or illness caused by fire, protect other property from damage caused by fire, and facilitate firefighting and rescue operations.

Click here to view the full fire code document.

What is the fire test for floor coverings?

Section C is the part of the Building Code relating to fire, and within this are six Clauses ( C1-C6).  Supporting the clauses are two Verification Methods and seven Acceptable Solutions outlining requirements for different building types.

The new code in 2012 introduced a different fire test method for floor coverings: Critical Radiant Flux tested to ISO 9239:1 2010. The fire test ISO 9239:1 2010 is only for floor coverings, not wall coverings.

To comply with the code, a building needs to be matched to a Risk Group, which is paired with an Acceptable Solution.  Risk Groups are assigned depending on the buildings use; multiple use buildings should follow the requirements of the most onerous relevant Acceptable Solution.

-       C/AS1 is the Acceptable Solution for Buildings with Sleeping (residential) and Outbuildings, Risk Group SH

-       C/AS2 is the Acceptable Solution for Buildings with Sleeping (non-institutional), Risk Group SM

-       C/AS3 is the Acceptable Solution for Buildings where Care or Detention is provided, Risk Group SI

-       C/AS4 is the Acceptable Solution for Buildings with Public Access and Educational Facilities, Risk Group CA

-       C/AS5 is the Acceptable Solution for Buildings used for Business, Commercial and Low Level Storage, Risk Group WB

-       C/AS6 is the Acceptable Solution for Buildings used for High Level Storage and other High Risk Purposes, Risk Group WS

-       C/AS7 is the Acceptable Solution for Buildings used for Vehicle Storage and Parking, Risk Group VP

The code calls for flooring to comply with a MINIMUM critical radiant flux when tested to ISO 9239-1 of between 1.2 and 4.5 kW/m² depending on the area within the building and the building's Risk Group. 


Critical Radiant Flux


1.1 Introduction and scope

This Acceptable Solution is one of three Acceptable Solutions that provide a means of establishing compliance with NZBC Clauses C1 to C6 Protection from Fire. It can be used for the building activities covered by risk groups specified in Paragraph 1.1.1 and described in Table 1.1. For risk group SH, please refer to Acceptable Solution C/AS1. For backcountry huts, please refer to Acceptable Solution BCH/AS1. Where a specific risk group (or risk groups) is mentioned in a subheading and/or within the text of a paragraph, that requirement applies only to the specified risk group(s), and does not apply to other risk groups. Words in italic are defined at the front of this document. Appendices to this Acceptable Solution are part of, and have equal status to, the Acceptable Solution. Figures and risk group icons are informative only; the wording of the paragraphs takes precedence.

Risk Group1

Risk Group1Risk Group2

This change in building code requirements won't affect your ability to specify the two most used floor coverings in our range - Tarkett Commercial Vinyl and Shaw Contract Carpet Tiles both achieve critical radiant flux values of between 6 and 8, far exceeding the minimum set out in the new code. 

Note also that ceramic and porcelain tiles are specifically assigned a nominal CRF of 4.5 kW/m² and do not require testing.

Appendix B Tiles


What is the fire test for wall coverings?

The Building Code uses a different fire test method for wall coverings: ISO 9705.  Tests performed under ISO 5660 and EN13501 are correlated to ISO 9705 so may be used as well. The results from the ISO tests provides a Material Group number: Group 1 is the most fire-resistant, through to Group 4.  The results from the EN test provide a Class number, with Class A as the most resistant, through to Class F.  All test methodologies allow for the provision of a smoke index rating (-S), which may or may not be required depending on the building's Risk Group.

Appendix C wall tests

Table from Appendix C, C/AS3

Internal Surface Finishes



 Table from NZ Building Code clauses C1-C6

Critical Radiant Flux Test

The inquisitive and technically minded amongst you may be wondering how the test works.  The test is designed to evaluate the tendency of a floor covering to spread flame when exposed to radiant heat.  It's quite straightforward - a radiant panel is set at a constant temperature, generating heat exposure along the length of the test sample material, ranging from 11kW/m² at one end to approx. 1kW/m² at the far end (see diagram below).  This is then left for 30 minutes, and the length of material burnt during this time is measured.  This measurement becomes the sample material's critical radiant flux value, a higher value is better as it means more energy is required to sustain the travel of flame across the material.


Interior surface finishes, floor coverings and suspended flexible fabrics

Surface finish requirements for walls and ceilings 4.17.1 Surface finish requirements shall be as specified in Table 4.3 for walls and ceilings.

Flooring 4.17.3

Flooring shall be either noncombustible or, when tested to IS0 9239-1, shall have a critical radiant flux of not less than that specified in Table 4.5 (refer to Appendix C2.1). 4.17.4 Paragraph 4.17.3 shall apply to flexible finishes such as carpets, vinyl sheet or tiles, and to finished or unfinished floor surfaces.

Educational buildings 4.17.7

Unsprinklered firecells containing classrooms, passageways and corridors of educational buildings need not comply with Table 4.3 provided all the following conditions are satisfied: a) The occupant load is less than 250, and b) The firecells are at ground floor level and are served by at least two exitways or final exits, and c) The material Group Number is no more than 2-S for surfaces 1.2 m or more above floor level, and d) The material Group Number is no more than 3 for surfaces less than 1.2 m above floor level.