Fire Engineering Investigation of Cold Formed Steel Framed House Fire

This report presents New Zealand’s first investigation of a fully developed fire in a light steel framed house. The outcomes of this investigation are to quantify the structural fire severity of the property at 9 Nuneaton Drive, Auckland and to use this information to better understand the performance of light steel frame houses in severe fires.

The HERA Report R4-127 and their FaST software were used as the principle tools in the analysis to simulate different fire conditions. The idea was to model the fire above and below the linings taking into account all the range of conditions that could have existed during the fire and to determine, through comparing the predicted failure times of the wall and ceiling linings with those observed, the likely fire load, boundary conditions and hence the likely structural fire severity and time temperature conditions.

It can be concluded that the house performed very well in the fire as the steel framing in the roof and walls did not collapse despite being exposed to the fully developed fire. A fire with a thermal inertia of 700 J/m2Ks0.5 and a fire load energy density of 300 MJ/m2 best represented the chain of events from the Fire Report and hence was the most realistic model that was analysed. The steel framing could have been cleaned and reused but it was more practical to replace it.

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