Has Cold Formed Steel got a fire rating? What happens in a fire?

Neither light steel framed construction nor light timber framed construction have a fire rating in themselves – both require the application of fire-resistant linings. When these are applied both can deliver whatever magnitude of fire resistance is required. 

Regarding performance of houses in fire, CFS has two very significant advantages over light timber framed construction. The first is that it is non-combustible. When fire burns through the linings it will not spread within the framing cavity in steel framing (whereas this is a major cause of hidden fire spread in timber framing). Electrical faults are the most common causes of fires in wall cavities – however these cannot ignite a steel frame. 

The second big advantage is that it does not increase the fire load. There is at least 20 kg of timber per square metre of floor area in a timber framed house. This is 75% of the design fire load of a house contents, which means that a timber framed house is carrying at least 1.75 times the fire load of a steel framed house. The higher the fire load, the more severe the fire. 

Given these two advantages it is not surprising that fire case histories show steel houses perform very well in house fires, with little or no damage to the framing structure. Indeed, if steel framed members are not visibly distorted, they can be left in place, cleaned and, if necessary, recoated.