Mixing 13/13R in a building with an enclosed parking garage

[Brian 2]

There have been other discussions about NFPA 13 or NFPA 13R in a building with mixed occupancies and quoting the below commentary section:

A common question is whether a mixed-occupancy building that contains a Group R occupancy could still use NFPA 13R for the design. If one of the mixed-use occupancies would require a sprinkler system throughout the building in accordance with NFPA 13, then a 13R system would not be allowed. If, however, the only reason a sprinkler system is being installed is because there is a Group R fire area within the building, then an NFPA 13R system would be an appropriate design choice. The areas that are not classified as Group R would require protection in accordance with NFPA 13.

If a building has an enclosed parking garage requiring sprinklers throughout per 2018 IFC 903.2.10, is NFPA 13 required throughout? Or is 13R above permitted because 903.2.10 does not identify NFPA 13 system is required via a reference to 903.1.1, it just says an "automatic sprinkler system"? For sake of discussion 3 story building with S2 enclosed parking on level 1 and R2 above.

 

[TheCommish]

I think you have to look at the seperation between the S2 and The R used

 

[Jay Smith]

Based on 903.3.1, an automatic sprinkler system must comply with 903.3.1.1 (NFPA 13) unless otherwise permitted by 903.3.1.2 (NFPA 13R) or 903.3.1.3 (NFPA 13D). The S-2 occupancy beneath other groups requires NFPA 13. It is required throughout the building, according to 903.2.10. The only provision to stop the extent of the building below the other groups is the 3-hour separation in 510.2.

I hope this question gets some discussion. What I found in the code surprised me a little, so maybe this is not the answer.