Fire-resistance rated construction, commonly referred to as passive fire protection, is a crucial component in safeguarding building occupants and protecting property from damage. The base philosophy behind providing fire-resistance rated construction is compartmentalizing the building in such a way that limits the effects of fire on structural components, slows the spread of the fire, and allows the building occupants enough time for safe escape.
Many industry professionals use the term “fire wall” or “rated wall” when discussing any fire-resistant rated wall assembly. However, not all fire-resistant rated wall assemblies are the same. In fact, Chapter 7 of the International Building Code (IBC) specifically identifies four separate fire-resistance rated wall assembly types: fire partition, fire barrier, smoke barrier, and fire wall.
Fire Partitions
A fire partition is the least restrictive of the four fire-rated wall assemblies mentioned. Fire partitions are primarily utilized for corridor wall construction and as tenant separations in malls and residential units. Like a fire barrier, a fire partition may extend from floor to roof deck above. A fire partition is not expected to completely stop the fire from spreading but rather slow down the fire spread enough to allow for additional time for occupants to escape.
Fire Barriers
Fire barriers serve a variety of purposes such as separating different occupancies, enclosing exits, shafts, and incidental use areas, and separating hazardous material control areas from other portions of the building. A fire barrier is designed to restrict the spread of fire across the assembly and can have a one to four-hour fire-resistance rating - i.e., the period of time, according to the IBC, a fire can be confined, continue to perform a structural function, or both. Although fire barriers typically provide a higher degree of protection than a fire partition, they lack the inherent structural integrity of fire walls. Fire barriers are constructed to span vertically from the floor to the roof above.
Smoke Barriers
A smoke barrier is very similar to a fire barrier and is typically used in specific applications such as Group I-2 and I-3 occupancies and Areas of Refuge. A smoke barrier is an assembly that is intended to restrict the movement of smoke but also has a one-hour fire-resistance rating. The biggest difference between a smoke barrier and a one-hour fire barrier is a smoke barrier only requires a 20-minute rated opening protection assembly (i.e., fire door/shutter), whereas a one-hour fire barrier requires a one-hour rated opening protection assembly.
Fire Walls
The fire wall is the most robust and restrictive of the four wall types indicated. A fire wall must provide a higher level of fire safety, continuity, and structural integrity than other types of fire-rated walls. The hourly rating requirement for fire walls ranges from two to four hours with three hours being the most common application.
Unlike other rated walls, the fire wall is required to span horizontally between exterior walls and vertically from the building ground floor slab to 30 inches above the roof deck (unless specific exceptions of the IBC are met). They are primarily used to subdivide a structure into separate buildings for the purposes of complying with IBC requirements such as allowable height and area requirements. Fire walls allow for collapse of the structure on either side of the fire wall without collapse of the wall under fire conditions.
Final Considerations for Fire-Rated Wall Assemblies
As always, proper maintenance and protection of openings in fire-resistance rated walls is of the utmost importance. All openings in fire-resistance rated assemblies should be properly protected in accordance with the applicable provisions of the IBC. It is also important to note that the indicated fire-resistance rating duration of an assembly (e.g.., one-hour, two-hours, etc.) does not guarantee that the assembly will prevent the spread of fire for that duration. All fire scenarios are different and have different effects on any given assembly. According to the IBC, a fire-resistance rating indicates how long a building element, component, or assembly maintains the ability to confine a fire while it continues to perform its structural function. Typically, this is determined by IBC-prescribed tests. So while fire-resistance ratings are helpful guideposts, they do not accurately predict how they’ll perform during a live fire event – it’s important to consult with a licensed fire protection engineer to determine the best fire-rated wall assembly.