In the construction of floor and roofs steel joists have been used with great success over the years. In some cases however these assemblies need to be protected in case of a fire. The easiest way to do this is a direct application of a fire resistant product, or to add a membrane that is heat and fire resistant.
As a rule, the steel joists for certain constructions manufactured today have a built-in quality of fire resistance. Complete assembly description are however obtainable, either from the manufacturer or from a body called the fire resistance directory. If, for example the rules of construction and the requirements for fire resistant steel joists are not followed, a building or construction can be declared unsafe by the building inspectorate. Repair costs are always an unnecessary burden. The materials used in construction, especially the steel joist, carry enormous amounts of weight, and if the materials used are low grade or below the required standard, the safety of the populace can be dangerously jeopardised.

To confine a fire to a certain area, or to curb spreading of the fire to other areas, the ability of the whole structure to act as fire protector is very important. Continuant structural performance to resist the passage of hot gasses, flames or excessive heat to exposed areas is called the fire endurance period. Standard tests can be done to determine a construction]s ability to withstand heat or fires, by monitoring the rise of temperatures on areas exposed to continue heat. The proper spacing of the steel joists is very important; the closer these fire resistant joists are spaced the more protection will be created. Elevated temperatures can adversely affect the properties of the materials used as well as the steel member’s structural values. The most important factor in material design is elasticity and yield stress.