NFPA 13R vs NFPA 13 Throughout for Mixed-Use?

1/15/2021

When applying NFPA 13R to a mixed-occupancy (R-2 and S-2) building, what is the definition of "incidental"?

The building in question is three stories of residential over a parking garage designated for residents only. Each residential floor is approximately 2,000 sqft and the garage is approximately 3,000 sqft. The building is type V-A (wood, combustible) throughout.

IBC 2015 Section 509 defines incidental as constituting less than 10% of a given floor.

Does this entire building require a full NFPA 13 system?

If possible, please provide a code basis, thank you!

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4 Comments

Dan Wilder

1/15/2021 08:10:19 am

Big rabbit hole of confusion but your question starts with what is considered "incidental" and provided the correct building code definition but transitions to if the building requires a full 13 system vs 13R which is separate from incidental use areas as they pertain to NFPA (an example being small ordinary hazard areas within a floor that has a light hazard calc).

There is some information missing (rated horizontal separations being a large one) that would further clarify an answer to your question but have a look through the two links before and let me know if that helps. These aren't the only articles, just two that came to mind and were recent.

https://www.meyerfire.com/blog/when-can-i-use-nfpa-13r-part-i

https://nfsa.org/2020/11/17/nfpa-13-vs-nfpa-13r-in-podium-and-mixed-use-construction/

Ryan J

1/15/2021 09:07:55 am

Section 903.3.1.2 of the 2015 IBC may be able to point you in the right direction for this issue.

sean

1/15/2021 09:16:18 am

The building code determines which standard(s) you can use for a given project.

If they took the area increase for sprinklers you have to use NFPA 13, but if you just add a single story of height you can use NFPA 13 or 13R per the building code.

Then you follow the respective standard. If the IBC allows for NFPA 13R and it is not disqualified for height the standard (NFPA 13R) has language to handle areas outside of dwelling units and how to handle private or public parking garages. In your case if the area increase does not apply, and the building isn't too tall an NFPA 13R for the building would most likely work. Keep in mind that NFPA 13R will tell you that the public garage and areas outside of the dwelling area will be handled by NFPA 13. That does not mean that project is covered by two standards, just that the controlling standard NFPA 13R would direct you to NFPA 13 to handle certain things.

Anonymous

1/20/2021 05:22:06 pm

We do many projects like this in Massachusetts where the state amendment to the occupancy table 903.2 reads,
Note a - For use group R and I-1 Buildings with an aggregate building area of 12,000 sq. ft. or more, and Mixed-Use Buildings, the sprinkler system shall be designed and installed throughout the structure in accordance with NFPA-13. Does this mean that buildings like the one described in this question or even 2 family R-3 use with a basement dedicated to storage (S-2) would require a full 13 system, assuming that storage is more than 10% of the story. This would essentially make any 3-5 unit residential building over a closed garage or with tenant dedicated storage not eligible for 13D or 13R.

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NFPA 13R vs NFPA 13 Throughout for Mixed-Use?

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