Ch. 6 - Fire and Smoke Resistant Assemblies

Delia Tacheny
INT 324 - Building Codes
Reading: The Codes Guidebook for Interiors

Keywords:

• 
  Passive systems
• Active systems
• Fire barriers
• Fire partitions
• Horizontal Assemblies
• Fire Areas
• Through Penetration
  
  

Fire Protection is at the core of Building Codes and Life Safety, especially considering that fires were one of the main reasons building codes formed in the first place. This chapter regarding Fire Safety focuses on different assemblies for fire and smoke resistance. A lot of this chapter overlaps with the previous topics and terms we have discussed this far. Fire and Life Safety codes affect basically every part of a building, focusing on prevention, early detection, control, and suppression. "Interior fire related codes focus on confining a fire to the room of origin and limiting the growth of the fire to prevent flashover."

There are two primary systems when it comes to fire and smoke resistance: passive and active. 

Passive systems focus on preventing, prohibiting, and containing fires; they include fire and smoke barriers and partitions (walls), horizontal assemblies (floors, ceilings, etc.), opening protectives (windows, doors, etc.), through-penetration protectives (fire-stops, draft stops, dampers), and finishes and furniture.

Active systems are those that must be activated in order to work against the fire; they include detection systems (detectors, fire alarms, communication systems), extinguishing and suppression systems (fire extinguishers, fire hoses, sprinkler systems), and emergency lighting.

Before we dive into the different assemblies, it is important to note as always that the code books will be the most helpful guide in an actual project, and this blog is NOT a detailed regurgitation of every graph and table. However, we will touch on the basics of each assembly. That being said, when it comes to fire codes and safety, the three primary factors that will dictate requirements are, occupancy type, construction type, and whether or not the building/space is sprinklered. 

The best way to prevent the spread of fire and smoke is through compartmentalization, which will keep any incident contained for at least a period of time. 

Fire walls are fire-rated exterior walls, and they are important to understand, but 

when it comes to interior fire-rated assemblies, there are three main options: fire barriers, fire partitions, and horizontal assemblies. (The NFPA doesn't use the term fire partitions; they simply vary the restrictions for fire barriers.) 

Fire barriers are walls with fire-resistant ratings. They are usually required to extended vertically from the top of a floor/ceiling assembly to the bottom of another; in the case of a suspended ceiling, the barriers must extend to the floor slab above. Additionally, the number of openings including doors and windows are limited. 

In the IBC, a fire partition is similar to a fire barrier but with slightly less restrictive requirements. 

Horizontal Assemblies are all the floor/ceiling/roof assemblies that are required to be rated. They extend from one rated or exterior wall to another, and wherever they intersect a fire barrier, the joints must be sealed. Openings and penetrations are also limited and must be protected. 

Fire-rated assemblies are used to create and separate fire areas, which are typically utilized to provide compartmentation and to stay below the area limitations requiring an automatic sprinkler system according to the fire code. Fire areas are also almost always required to separate hazardous use areas from another occupancy type. Occupancy and tenant separation will often need to have some level of fire-rating, but this is wholly dependent on the present occupancies and the overall project situation. 

Another important situation is when dealing with vertical shafts and means of egress - places in which fire and smoke could spread vertically throughout the entire building. The required fire ratings depend on the size of the opening and the number of stories it extends. 

Smoke is another threat to life safety. Smoke is driven through 5 primary movements: Buyonacy, Expansion, HVAC, the Stack Effect, and Wind. In the same way that some assemblies must be fire-rated, some must also be smokeproof. "This is usually required for stairs, elevators, and waste and linen chutes when the shaft extends through a certain number of stories or the building is a certain height. To make them smokeproof, the walls must meet the requirements for smoke barriers and all openings into the shaft must automatically close on detection of smoke. A smoke stop or smoke door is usually required. This door is typically connected to the smoke detection and standby power systems in the building. And, this is a door specially designed to close tightly and inhibit the passage of smoke."

Often time, rated assemblies will also require rated openings which means rated doors, windows, and glazing, including door frames, hardware, framing, etc. Some of the most common types of rated glazing are wired glass, specialty tempered glass, glass block, clear ceramics, and laminated glass. All of these things are tested primarily through the NFPA and UL. 

Last, but not least, "a through penetration is defined as an opening that pierces the entire thickness of a construction assembly, such as a wall or floor/ceiling assembly." Penetrations must be protected by preventative assemblies such as fire and smoke stops, draft stops, fireblocking, and fire dampers. These systems each have varying purposes and functions that can be looked into further on their own. 

As designers it is important to be aware of construction assemblies and fire-ratings so that we can create functional and safe designs, and clearly communicate with the architect and contractor on the job. 

Source(s):

Kennon, Katherine E., and Sharon Koomen Harmon. “Ch.6: Fire and Smoke Resistant Assemblies.” The Codes Guidebook for Interiors, John Wiley & Sons, Inc., Hoboken, NJ, 2022.