SR417 Fire resistance requirements in single-storey industrial and warehouse buildings (March 2019)

An investigation into fire resistance requirements applied to external walls located near a property boundary in single-storey industrial and warehouse buildings in New Zealand has been carried out. Currently specified fire resistance ratings in prescriptive compliance documents are much higher than similar requirements in many overseas jurisdictions. The aim of this study was to understand why this is the case and to propose a risk-based methodology for setting appropriate levels of fire resistance in regulation.

A probabilistic analysis using Latin hypercube sampling methods in conjunction with a fire severity model known as the graphical time-equivalence method has been used to construct probability distributions for the required fire resistance ratings. Cumulative frequency distribution curves showing the fire resistance percentiles are presented. It was found that the methodology can be applied to buildings within the scope of C/AS5 but may not be strictly applicable to very high load densities such as warehouses in C/AS6 due to the underlying limitations of the parametric time-temperature equations. It is concluded that current fire resistance levels in C/AS5 and C/AS6 for external boundary walls could be reduced, depending on the level of acceptable risk and the design percentile values set by the regulator.