Steel is non combustible.
The number of deaths from house fires is relative small and represented 1.5% of accidental deaths and 0.06% of all deaths in 1998. Should damage occur, the materials of construction could mean the difference between repairing your home or completely rebuilding it.
Fixed wiring under floors and in walls and ceiling spaces is frequently concealed and not readily inspected. If it was damaged when originally installed, has been damaged by later building processes, or has deteriorated through other causes, its degraded condition is generally unknown. Arcing between conductors, or resistive heating under overload conditions, can lead to ignition of electrical components and adjacent combustible materials. In fact, electrical distribution accounts for around 10% of all fires in dwellings
Steel framing can make ignition and fire spread less likely in two ways:
* Faulty wiring is more likely to short to earth, tripping the building’s electrical safety switches and alerting to the need for fault investigation.
* Steel framing is non-combustible, and therefore cannot support the growth of a fire originating in electrical wiring.
An electrical fire resulting from faulty appliances and leads is covered below.
The primary causes of contents fires in houses, townhouses and units are cooking and heating appliances (Ref 2). Cooking appliances alone account for around 50% of all dwelling fires. Other causes include faulty heating and other appliances, accidental ignition of combustibles, arson and children’s accidents.
The preferred means of improving occupant safety is to give early warning to allow plenty of time for evacuation whilst a fire is small. The introduction of smoke alarms has coincided with a drop in the deaths from house fires. As about 50% of house fires occur in the kitchen, the provision of fire blankets or extinguishers would reduce the amount of damage. It is not practical to control and reduce the amount of combustible fuel available to burn in houses.
The Building Code of Australia sets the minimum requirements for the construction of all buildings, including Class 1 houses, townhouses and units. The Code is primarily concerned with safety of the occupants so that they may safely exit and avoid the toxic effects resulting from the spread of smoke/fire. This has led to introduction of smoke detectors and fire resistance requirements for walls close to the site boundaries on all new houses.
The growth of a fire within a room primarily depends on the amount of fuel available, the combustibility of the materials involved and the amount of oxygen available. The steel frame is protected from the fire by the plasterboard. Fire tests under taken at the Warrington Fire Research for Boral Plasterboard indicate a rating of 15-30 minutes in a standard fire test for standard plasterboard with steel framing. In a real fire the period would generally be expected to be considerably longer.
For other classes of buildings the Building Code of Australia extends its provisions to a greater range of active fire safety measures, e.g. sprinklers are required in some occupancies, and increased requirements for the fire resistance levels of the structural members and the separation between fire compartments. These provisions are aimed at providing safe exit paths for occupants and stopping the spread of the fire between compartments within a building and to other buildings. Resistance requirements are specified for walls, floors and other structural elements depending on the number of stories and the plan area of the building fire.
Steel frames do not ignite, propagate or add fuel to a fire. Substituting steel for combustible framing materials, and avoiding flammable or combustible materials in roof spaces and cavities, will help reduce the consequences of an uncontrolled contents fire.
1. Babrauskas, V: “How Do Electrical Wiring Faults Lead To Structure Ignitions?” Proceedings of the Fire & Materials Conference, San Francisco, 2001.
2. “Australian Social Trends 2000, Housing Stock: Home Fire Safety”, Australian Bureau of Statistics, 2000.