Two important fire safety concepts are fire-resistive construction and fire suppression. Let's look take a closer look at these two concepts and what they do.
Fire resistive Construction - Know your definitions.
The basic building blocks of any concept is the meanings behind the words being used to describe the concept. Building code is no different, in fact, the second chapter of the code is nothing but definitions. It's important to read through these and understand them, because they may be slightly different that what you think, or they may decipher between two elements that you thought were the same but are actually different. Among the most critical aspects of building code is it's emphasis on fire safety. Let's start at fire safety and define 5 important definitions to understand when working through fire safety in a building. As you read through these, fire resistive assemblies, they are listed from most stringent to least. Fire walls, fire barriers and fire partitions often get lumped together by people when discussing a project. Take the time to politely correct someone when they are using the wrong term, the differences between these three are paramount to life safety.
Section 706 IBC. Fire wall. A fire-resistance-rated wall having protected openings, which restricts the spread of fire and extends continuously from the foundation to or through the roof, with sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of the wall. It's easy to spot a fire wall from the street, these are the walls that protrude above a roof on an apartment building. These walls must be designed to remain standing if the structure on either side collapses, but does not need to remain standing if both sides collapse. This is because a fire wall is designed to stop a fire from passing beyond it's division. A fire wall essentially creates a division so something that looks like a single building can actually considered two separate freestanding buildings. There are a few requirements for a wall to be considered a firewall, this list only includes a few major talking points and not complete:
A fire wall will extend from the foundation to 30" above the roof (most of the time).
A fire wall will have a fire resistance rating of 2-4 hours based on occupancy.
A fire wall will have protected openings.
A fire wall will be vertical without horizontal offsets.
Fire walls are always vertical and do not include horizontal assemblies. If a fire wall sits on a lot line, it is called a party wall and cannot have openings.
2. Section 707 IBC. Fire barrier. A fire-resistance-rated wall assembly of materials designed to restrict the spread of fire in which continuity is maintained. While the definition exclusively calls out fire barriers as walls, the code commentary explains that a horizontal assemblies can also be fire barriers. Fire barriers called out in section 707 of the IBC. Fire barriers must extend floor to underside of sheathing or slab above. A fire barrier is a separation that includes stairways, elevators, occupancy groups etc.
3. Section 708 IBC. Fire partitions. A vertical assembly of materials designed to restrict the spread of fire in which openings are protected. Fire partitions are rated at 1 hour, sometimes, but rarely a 1/2 hour. Openings in fire walls need to be protected as well. These partitions separate dwelling units, corridors from dwelling units, elevator lobbies and more.
4. Section 709 IBC. Smoke barriers. A continuous membrane, either vertical or horizontal, such as a wall, floor or ceiling assembly, that is designed and constructed to restrict the movement of smoke. Smoke barriers prevent the movement of smoke by creating compartments. Smoke barriers are comprised of floor and ceiling assemblies that rated 1 hour. Smoke barriers must also be continuous through concealed spaces such as floor assemblies and soffits etc.
5. Section 711 IBC. Horizontal Assemblies. A fire-resistance-rated floor or roof assembly or materials designed to restrict the spread of fire in which continuity is maintained. Horizontal assemblies are floors and roofs with a rating of 0-2 hours but can be up to 4 hours dependent on the requirements of corresponding fire-resistant assemblies. Structure that supports the horizontal assembly must have rating of 1 hour or more.
2. Know your fire suppression systems.
There are three types of sprinkler systems called out in the IBC.
NFPA 13,
NFPA 13R
NFPA 13D
The first is the most robust, NFPA 13 is a full system designed for commercial use. It is the most expensive, so even though it can be used in any case it makes sense from a budget sense to always look to see if an NFPA 13R or NFPA 13D system will work. NFPA 13R is a residential system four residential buildings under 4 stories. NFPA 13R systems put an emphasis on human safety and do not protect against property damage. This means the system will not need to protect unoccupied spaces such as attics. NFPA 13D is the least robust system, and also the least expensive. This system is designed for one and two family homes.
A vertical water supply system that can be used by the fire department to suppress a fire is called a standpipe. Standpipes come in three classes, Class I, Class ll, and Class lll. These classes designate the size of hose connections. A standpipe system is significant portion of the cost for a sprinkler system, it may make sense to add a full sprinkler system if a standpipe is mandatory.
When designing a building, first look at whether a sprinkler system is needed or not. Sprinkler systems often come with other benefits in the code sometimes referred to as trade-offs. The code offers numerous opportunities to increase building square footage or height if you add a sprinkler system that is not mandatory. The theory would be that a sprinklered building is safer and therefore the risk to human life in a fire is greatly reduced, making it safer for a larger building with more people and longer paths of egress.