NFPA 13R Building Converted to Mixed Occupancy
A four-story, 48 ft high apartment building was built in 2008 with an NFPA 13R system. The system has a single 4 in riser, 1½ in branch lines, and residential sprinklers in dwelling units. Sprinklers were omitted from bathrooms under 55 sq ft, closets under 24 sq ft, and the ground-floor laundry. The owner now converts the ground-floor laundry and manager’s office into a 1,200 sq ft restaurant with a commercial range and a 6 ft hood. The building remains four stories and 48 ft high. The local code official says the building can keep the 13R system because it is still primarily residential. The contractor proposes adding sprinklers only in the restaurant and keeping the existing 13R omissions. The water supply is a 6 in city main with 900 gpm at 50 psi residual. The restaurant will have a grease-laden hood.
1. Evaluate whether the existing 13R system can remain as the sole sprinkler system for the building after the restaurant is added.
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No. NFPA 13R is limited to residential occupancies, and a restaurant is a commercial occupancy. The presence of a commercial cooking range and grease-laden hood means the restaurant must be protected under NFPA 13, with hood suppression under NFPA 96. The 13R omission rules for bathrooms and closets apply only to the residential portions; they cannot be extended to the restaurant. Keeping the 13R system as the sole system would leave the commercial occupancy without the required design density and would not address the cooking hazard. The minimum acceptable upgrade is to provide an NFPA 13 system for the restaurant and verify that the combined water supply can handle both systems. If the restaurant is not separated from the residential portion by a fire barrier, the code official may require the entire building to be upgraded to NFPA 13. The existing 900 gpm at 50 psi residual must be re-evaluated for the new combined demand, not assumed adequate.
2. The contractor plans to omit sprinklers in the new restaurant restroom, which is 48 sq ft, and in a 20 sq ft electrical closet. Is that acceptable? Explain.
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No, not automatically. The 13R omissions were allowed because the building was a residential occupancy; those allowances do not transfer to the restaurant. Under NFPA 13, omission from a bathroom is limited to specific conditions, such as noncombustible construction and no combustible storage, and it is not an automatic right based on size alone. A 20 sq ft electrical closet is also not automatically exempt; if it contains combustible wiring, storage, or equipment, sprinkler protection is generally required unless a specific code exception is documented. The contractor must either provide sprinklers in both spaces or cite and satisfy the exact NFPA 13 omission criteria for each space. Because the restaurant is a new commercial occupancy, the default should be to sprinkler the restroom and electrical closet unless the code official approves a written exception.