Description

There is no specific method for calculating the thermal impact of fires from roofs in New Zealand Building Code Verification Method C/VM2 or in the scientific literature. BRANZ investigated adapting related published research and modelling approaches for this purpose, validated by limited small-scale experimental fires. The initial modelling suggests that New Zealand’s general and specific Building Code requirements to mitigate fire spread from lower roofs are conservative in some, but not all, realistic fire situations. The recommended one-size-fits-all approach may not be appropriate for some building configurations.

Fire spread between adjacent buildings can occur when a fire plume develops above a roof and impacts adjacent taller buildings.

Scope

In this research:

• The causes of a fire plume above a roof
• Available models and small-scale validation
• Building Code requirements relating to fire spread from lower roofs to adjacent buildings
  • Building Code general performance-related requirements
  • Specific prescriptive requirements in Acceptable Solutions C/AS1 and 2019 C/AS 2 (previously C/AS2 to C/AS7)
• Modelling heat flux from a lower roof on adjacent buildings
• Discussion
• Recommendations