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