What is the minimum calculated design area for a dry system protecting a light hazard attic space with a roof slope exceeding a rise of 2 units in a…

NFPA 13 sets the starting remote-area for Light-Hazard occupancies at 1,500 ft² (140 m²).

(1) Quick-response sprinklers in Light-Hazard spaces permit a 40 % reduction, but never below 900 ft².

1,500 ft² × 0.60 = 900 ft².

(2) Because the system is dry, §11.2.3.2.5 (2019 ed.) requires a 30 % increase to the computed remote-area.

900 ft² × 1.30 = 1,170 ft² (≈108.7 m²).

Roof slope or attic height does not require any further remote-area adjustment; therefore the minimum calculated design area is 1,170 ft².

A. 1,521 ft² – applies only the dry-pipe 30 % increase to the 1,500 ft² base and ignores the quick-response reduction.

C. 1,950 ft² – multiplies the 1,500 ft² base by 1.30 but omits the quick-response reduction; result is too large.

D. 2,535 ft² – assumes multiple compounding increases (slope, dry, no QR reduction); exceeds NFPA 13 requirements for this scenario.

1. NFPA 13, Standard for the Installation of Sprinkler Systems, 2019 Edition:

• §11.2.3.1.1(1) – Base design area 1,500 ft² for Light Hazard.

• §11.2.3.2.3 & Fig. 11.2.3.2.3(b) – 40 % area reduction for quick-response sprinklers; minimum 900 ft².

• §11.2.3.2.5 – 30 % area increase for dry-pipe systems.

2. NFPA Fire Protection Handbook, 20th ed., Vol. I, Chap. 11 “Hydraulic Design of Automatic Sprinkler Systems,” pp. 11-52–11-54 – discussion of QR reductions and dry-system increases (confirms NFPA 13 text).

3. University of Maryland, ENFP 312 “Water-Based Fire Protection,” Lecture 9 notes, slide 28 – illustrates 0.60 QR factor followed by 1.30 dry-pipe factor (light-hazard example).