Use NFPA 13 & 13R in Mixed-Occupancy?
If you are working on a residential project that also contains other occupancy types you may have wondered if you are allowed to use an NFPA 13R sprinkler system even though the project contains non-residential occupancies.
To answer this question there are a few steps you need to take.
First you need to determine if your Group R occupancy is eligible for an NFPA 13 R system in the first place. IBC Chapter 903.3 describes where you are permitted to use an NFPA 13R System.
Under the 2021 IBC, the criteria includes buildings that:
Are 4 stories or fewer above grade plane
Where the floor level of the highest story is 30 feet or less above the lowest level of fire department vehicle access.
Where the floor level of the lowest story is 30 feet or less below the lowest level of fire department vehicle access.
If the Group R occupancy in your building does not meet all of these criteria, you need to design the sprinkler system for the entire building to NFPA 13.
If the Group R occupancy does meet these criteria, then you may be able to provide an NFPA 13R system in the residential areas, but there are a few requirements you need to consider.
IBC Chapter 508 offers three different approaches to mixed occupancy buildings: accessory, separated and non-separated. You can check out the module on this topic for more specific information, but the important part here is that each of these approaches dictate how you apply the IBC Chapter 9 requirements to the building.
If you choose a nonseparated mixed occupancy approach, the most restrictive requirements of IBC Chapter 9 apply to the entire nonseparated building area. Since an NFPA 13 sprinkler system is the more restrictive standard over NFPA 13R, that would then apply to the entire building, including the residential area.
If you choose a separated mixed occupancy approach, the requirements of Chapter 9 are applied individually to each occupancy that is separated. This means that if your residential occupancy is separated from adjacent occupancies in accordance with IBC Table 508.4, you are permitted to provide an NFPA 13R system in the residential area while still providing an NFPA 13 system other area.
Looking at IBC Table 508.4, there are different requirements for buildings that are in the “S” category meaning equipped throughout with an NFPA 13 system versus the “NS” category which means buildings that are not equipped throughout with an NFPA 13 system. Since we are considering where an NFPA 13R system can be used, our building would not be sprinklered throughout with an NFPA 13 system, so we need to use the “NS” category.
Reading IBC Table 508.4 for Group R occupancies, a 2-hour fire resistance rated separation is required from Groups A, B, E, F, M and S. This approach would not be permitted if there are Groups I or H in the building.
When taking this strategy, it important to note that many code allowances are based on the building be fully sprinklered in accordance with NFPA 13. If part of the building contains and NFPA 13R system, you would not be able to use these provisions. A few examples of these allowances are allowable height and area, and certain egress requirements in Chapter 10.
In summary, if you’re are working on a residential project that also contains other occupancy types, you may be able to provide an NFPA 13R system in the residential areas while providing an NFPA 13 system in the other occupancies.
If your residential occupancy meets the criteria for using an NFPA 13R system and you are providing sufficient separation from other adjacent occupancies, this could be a viable approach for your project.
I’m Chris Campbell, this is MeyerFire University.
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