Restaurant Proposed as NFPA 13R
A contractor proposes NFPA 13R sprinkler protection for a new 6,000 sq ft restaurant building in Minnesota. The building is two stories: 4,500 sq ft of dining, bar, and commercial kitchen on the first floor, and 1,500 sq ft of basement storage. The contractor says 13R is allowed because the building is low-rise and the kitchen has a listed hood suppression system. The water supply is a 6 in main with 65 psi static and 22 psi residual at 1,000 gpm. The contractor's one-line shows a 13R calculation with four sprinklers in the dining area. The AHJ's plan reviewer notes that the restaurant seats 180 people and that the basement stores paper goods and linens. No hydraulic calculations for the kitchen or storage have been submitted.
1. Is NFPA 13R permitted for this restaurant? Explain.
Read the worked answer
No. NFPA 13R is limited to residential occupancies within its stated height and use limits. A restaurant with dining, bar, commercial kitchen, and storage is not a residential occupancy, so the low-rise argument does not make 13R applicable. The listed hood suppression system protects the cooking equipment, not the building's general sprinkler demand, and it does not substitute for an NFPA 13 system. The designer must use the adopted NFPA 13 standard and submit calculations for the actual occupancy hazards.
2. How should the dining, kitchen, and basement storage be classified and calculated?
Read the worked answer
The designer should classify each area using the adopted NFPA 13 occupancy hazard rules. Dining and bar areas are typically light hazard; the commercial kitchen is at least ordinary hazard and may require a higher classification depending on cooking and grease loading; basement storage of paper goods and linens is likely ordinary hazard and may be higher depending on storage height and arrangement. The calculation must use the most demanding remote area, correct density and area, hose allowance, and sprinkler spacing. A four-sprinkler dining-room calculation is not representative. The designer should also confirm whether the hood suppression system affects any sprinkler omission, which it generally does not for the building protection.
3. Is the water supply likely adequate? What must the contractor do next?
Read the worked answer
The 22 psi residual at 1,000 gpm may be inadequate once the ordinary hazard kitchen or storage demand, hose allowance, and safety margin are included. The contractor must plot the supply curve against the calculated demand rather than rely on static pressure. If the demand exceeds the available pressure, the contractor should propose a fire pump, improved service, or a revised design that the AHJ accepts. The next submittal should include hydraulic calculations for the most demanding area, a water supply curve, and cut sheets. Approval should not be based on the 13R one-line.