Fire walls in buildings are essentially structural tools to prevent further spread of fire. As detailed in Chapter 7 of the International Building Code, a fire wall is a fire-resistance-rated wall with protected openings. It restricts the spread of fire and extends continuously from the foundation to or through the roof. This wall’s structural stability is sufficient to withstand the collapse of construction on either side without the wall collapsing under fire conditions.
Fire-resistant walls are meant to contain a fire to a room or building for a certain time period to allow sufficient time to discover a fire, control it, and evacuate the building if necessary. The wall's rating indicates how long it can keep a fire from spreading. This rating is determined either by using procedures developed by the American Society for Testing and Materials that simulate actual fire conditions or by employing the tables developed by the IBC.
A fire-resistance rating is the number of minutes or hours a structure can withstand a fire simulation test. A one-hour rating indicates that a wall constructed like the one tested will contain flames and high temperatures and support its full load for at least one hour after the fire begins. Similarly, a two-hour rated wall will contain the fire for two hours and a three-hour rated wall for three hours.
“Where there is an accessible concealed floor, floor-ceiling or attic space, fire walls, fire barriers, fire partitions, smoke barriers, and smoke partitions, or any other wall required to have protected openings or penetrations shall be effectively and permanently identified with signs or stenciling in the concealed space. Such identification shall: