C/VM2 Framework for Fire Safety Design - Amendment 6
Limited combustible materials have been added as a new compliance option, covering a material which is classified as A2 in accordance with to BS EN 13501-1. Limited combustible materials can be used without restrictions as claddings and wall cladding systems (if forming all substantive components of a wall cladding systems).
Under the design scenario (HS) Horizontal fire spread, the option of using an automatic sprinkler system supplied by two independent water supplies to avoid restrictions on the amount of unprotected area has been removed. Additional exemptions on the amount of unprotected area have been provided.
It has been made clear with the Design scenario (VS): External vertical fire spread, that fire spread within the external wall cladding system is a consideration to be addressed.
"Appendix C (normative): Methodology for design scenario HS: Horizontal fire spread (Tabular Data)" has been added. This Appendix can be used to satisfy Method B of design scenario HS: Horizontal fire spread. The bulk of this information was previously contained within a separate commentary document.
C/AS2 Acceptable Solution for Buildings other than Risk Group SH Amendment 2
Content in relation to claddings and the control of external fire spread has been altered and expanded. A key concept to be aware of is the distinction between cladding materials and external wall cladding systems. A cladding material is the exterior components including cladding, rigid air barriers, insulation products, sheet materials or blankets and filler materials (not including gaskets, sealants etc.). An external wall cladding system includes cladding materials and framing elements, as well as other components used to construct the wall. MBIE has issued guidance (Fire-performance-of-external-wall-cladding-systems) on this subject.
The following provides a brief commentary on the control of external fire spread in relation to cladding materials and external wall cladding systems as contained in NZBC C/AS2, 5.8 External cladding systems. This topic is distinct from fire resistance ratings of walls, which is covered elsewhere in the acceptable solution.
Other Amendments to C/AS2 include:
- Cladding materials are exempt from testing on walls located at a distance greater than or equal to 1.0m from a relevant boundary with a building height less than 10m, except for buildings containing risk group SI (care or detention).
- Risk group SI requires all cladding material to be non-combustible or limited combustible, or tested in accordance with ISO 5660 or AS/NZS 3837 (and meet specific requirements stated in C/AS2) to achieve a Type A or Type B classification.
- Cladding materials located less than 1.0m from a relevant boundary or cladding materials on multi-level buildings having a building height of 10m or more shall be non-combustible or limited combustible materials, or tested in accordance with ISO 5660 or AS/NZS 3837 (and meet specific requirements stated in C/AS2) to achieve a Type A classification.
- Building height parameters have been further codified with the addition of requirements for multi-level buildings ≥ 25m in height. At this height, the entire external wall cladding system is taken into consideration. Compliance of external wall cladding system can be demonstrated by the exclusive use of non-combustible or limited combustible materials, or by testing / classification with the nominated standards.
- An entire compliant external wall cladding system can also be used to satisfy the requirements of multi-level buildings with a height of 10m or more.
- Limited combustible material (classified as A2 to BS EN 13501-1) is a new solution added to C/AS2. Non-combustible and limited combustible materials and wall cladding systems can be used without restriction, with no proximity to boundary or building height constraints
- An additional testing option (BS EN 13501-1) to demonstrate compliance for non-combustible materials has been added.
- The definition of Suite (firecell providing residential accommodation) has been extended to include transient and educational accommodation.
- Subtle changes to Fire safety systems in early childhood centres in relation to escape heights.
- Subtle clarifications to define requirements in relation to single escape routes.
- Specific requirements for theatres, exhibition areas and retail spaces have been extended to include clarity on relationship with related risk groups.
- The extent of exceptions to the use of cavity barriers to close openings within a concealed space against the passage of fire, or to restrict the spread of fire have been reduced.
- Table 5.1 Maximum permitted areas of fire resisting glazing (m²) updated with changes to distance and area relationships.
- It has been confirmed that a roof eaves construction includes the guttering or spouting. This would trigger the need for fire rating if the roof eave then extended to within 650mm of a relevant boundary (although the guttering or spouting need not be fire rated).
- The option of using sprinklers for the protection of fire spread from an adjacent lower roof has become more onerous, requiring sprinklers to be provided throughout the building.
- The option of using an external wall cladding system incorporating an externally applied combustible insulant on buildings of three or more floors has been removed.
Effect on Masterspec sections.
Several cladding sections and curtain walling sections have been altered to accommodate these changes, typically to ensure references to NZBC tables and clauses in the Masterspec sections match the revisions to the acceptable solution and verification methods. A number of these sections have been more extensively altered to accommodate the expanded methods and solutions relating to the control of external fire spread.
As part of this process the Masterspec team has also developed additional content including guidance to accommodate manufacturers and suppliers taking advantage of the new testing options available.