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CBO
A recent clarification sheds light on a recurring question in the code enforcement community: Is sprinkler system supervision required for a two-family home, particularly when it is regulated under the International Building Code (IBC) instead of the International Residential Code (IRC)?
The issue stems from a scenario involving a four-story, two-family dwelling classified as Group R-3 under the 2021 IBC. Because the IRC limits two-family dwellings to a maximum of three stories, the IBC governs the design and construction of this building.
The focus is on Section 903.4 of the 2021 IBC, which requires sprinkler systems to be electrically supervised. However, Exception 1 under this section exempts “automatic sprinkler systems protecting one- and two-family dwellings.” The question is whether this exemption only applies to NFPA 13D systems—which are typically used in single- and two-family homes with a combined domestic and sprinkler supply—or whether it also includes NFPA 13R systems or even full NFPA 13 systems when required by other building factors such as height or construction type.
According to the ICC's official interpretation—an opinion also applicable to the 2024 IBC—the answer is clear: No electrical supervision is required for an automatic sprinkler system in a one- or two-family dwelling under Exception 1 of Section 903.4, regardless of whether the system is NFPA 13D or 13R, and regardless of whether there are separate water supply lines for domestic and sprinkler service.
The commentary acknowledges that while the historical intent of this exception has been associated with NFPA 13D systems, the code text does not limit its application to any specific NFPA sprinkler standard. As long as the structure is classified as a one- or two-family dwelling, the exemption stands.
However, code officials must still consider other factors that may mandate the use of NFPA 13 or 13R systems instead of 13D. In this case, the four-story height pushes the building beyond what is permitted for Type VA or VB construction protected only by an NFPA 13D system. Per Table 504.4 of the 2021 IBC, a taller structure would likely require a more robust construction type or the use of an NFPA 13 or 13R system to comply.
It’s important to note that Section 903.2.8 generally requires all Group R fire areas to be sprinklered under Section 903.3, but does not prescribe which NFPA system must be used. The decision depends on other factors, such as height, construction type, and whether any trade-offs are taken under the code.
In conclusion, regardless of whether the automatic sprinkler system is designed under NFPA 13D or 13R, and regardless of whether the water supply is shared or separated, electrical supervision of the system is not required under Section 903.4, Exception 1, provided the building is a one- or two-family dwelling. This interpretation brings clarity to a gray area and reinforces the need to evaluate each case based on occupancy classification, height, and applicable code sections.
The issue stems from a scenario involving a four-story, two-family dwelling classified as Group R-3 under the 2021 IBC. Because the IRC limits two-family dwellings to a maximum of three stories, the IBC governs the design and construction of this building.
The focus is on Section 903.4 of the 2021 IBC, which requires sprinkler systems to be electrically supervised. However, Exception 1 under this section exempts “automatic sprinkler systems protecting one- and two-family dwellings.” The question is whether this exemption only applies to NFPA 13D systems—which are typically used in single- and two-family homes with a combined domestic and sprinkler supply—or whether it also includes NFPA 13R systems or even full NFPA 13 systems when required by other building factors such as height or construction type.
According to the ICC's official interpretation—an opinion also applicable to the 2024 IBC—the answer is clear: No electrical supervision is required for an automatic sprinkler system in a one- or two-family dwelling under Exception 1 of Section 903.4, regardless of whether the system is NFPA 13D or 13R, and regardless of whether there are separate water supply lines for domestic and sprinkler service.
The commentary acknowledges that while the historical intent of this exception has been associated with NFPA 13D systems, the code text does not limit its application to any specific NFPA sprinkler standard. As long as the structure is classified as a one- or two-family dwelling, the exemption stands.
However, code officials must still consider other factors that may mandate the use of NFPA 13 or 13R systems instead of 13D. In this case, the four-story height pushes the building beyond what is permitted for Type VA or VB construction protected only by an NFPA 13D system. Per Table 504.4 of the 2021 IBC, a taller structure would likely require a more robust construction type or the use of an NFPA 13 or 13R system to comply.
It’s important to note that Section 903.2.8 generally requires all Group R fire areas to be sprinklered under Section 903.3, but does not prescribe which NFPA system must be used. The decision depends on other factors, such as height, construction type, and whether any trade-offs are taken under the code.
In conclusion, regardless of whether the automatic sprinkler system is designed under NFPA 13D or 13R, and regardless of whether the water supply is shared or separated, electrical supervision of the system is not required under Section 903.4, Exception 1, provided the building is a one- or two-family dwelling. This interpretation brings clarity to a gray area and reinforces the need to evaluate each case based on occupancy classification, height, and applicable code sections.