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CHANGES TO FIRE REQUIREMENTS FOR EXTERNAL CLADDING

Published 29 March 2017

Amendment 4 of NZBC C/AS2, C/AS4 to C/AS6, has deleted from Paragraph 5.8.3 dispensation from external cladding requirements for buildings sprinklered and less than 25m high. So all cladding for buildings over 7m high will now require a fire test. Cladding within 1m of the boundary (or in Risk Group SI using C/AS3) shall be fire tested regardless of height. Sprinklers no longer provide any dispensation for cladding (except for one case in NZBC C/AS1).

The test, is the small-scale cone calorimeter test to ISO 5660.1 that provides a total and peak heat release rate of the material.

Non-combustible materials would meet the requirements without testing, for example concrete, brick/block, ceramic tile, aluminium, glass, steel, cellulose fibre-cement products with applied finishes/coatings less than 1mm thick. However, timber products would usually not meet the above requirements without an application of a fire retardant treatment.

There are particular testing requirements for the likes of aluminium sandwich cladding panels, where the external metal has a melting point below 750°C (refer to C7.1.5 of the Acceptable Solutions). This requirement and the international history of fires with these sorts of panels is the main reason for this amendment.

Alternative wall assembly testing is allowed using the National Fire Protection Association NFPA 285 (Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components).


Table A - External cladding fire performance requirements

This Masterspec table gives the maximum Peak Heat Release (100kW/m² or 150kW/m²) and the maximum Total Heat Release (25MJ/m² or 50MJ/m²) to ISO 5660.1 permitted.  These are expressed in the table as, 100kW/m² & 25MJ/m², or 150kW/m² & 50MJ/m².

 

ACCEPTABLE SOLUTION

BUILDING HEIGHT

DISTANCE TO
BOUNDARY <1m

DISTANCE TO
BOUNDARY ≥1m

NZBC C/AS1

≤10m

100kW/m² & 25MJ/m²

No requirement

>10m

100kW/m² & 25MJ/m²

150kW/m² & 50MJ/m² (no requirement if sprinklered)

NZBC C/AS3

0 - 7m

100kW/m² & 25MJ/m²

150kW/m² & 50MJ/m²

>7m

100kW/m² & 25MJ/m²

100kW/m² & 25MJ/m²

NZBC C/AS2, C/AS4 - C/AS6

0 - 7m

100kW/m² & 25MJ/m²

No requirement

>7m

100kW/m² & 25MJ/m²

150kW/m² & 50MJ/m²

 

Notes to table:

  • Check the Code for detailed project requirements with the particular Acceptable Solution being used.
  • Height is "Building height" as defined in the NZBC C Definitions.
  • NZBC C/AS3 - This covers Risk Group SI. For >7m height and >1m from boundary there is no requirement for a single storey building.
  • NZBC C/AS1 - Distance applies if angle is less than 90°. Boundary is actual or notional. Does not apply to household units in the same building. (Refer C/AS1 table 5.1).

MBIE article Changes To Fire Requirements For External Cladding

https://www.building.govt.nz/about-building-performance/news-and-updates/codewords/codewords-issue-77/changes-fire-safety-external-cladding/

 

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