Because the beams are 26 in. deep but are spaced only 7 ft (2.1 m) apart, the ceiling is classified by NFPA 13 as “obstructed construction – beams spaced 7 ft 6 in (2.3 m) or less.” When a standard upright sprinkler is installed in the center of every bay formed by such closely-spaced beams, NFPA 13 directs that the installation be treated the same as for a smooth ceiling; therefore the deflector distance limits in Table 8.6.4.1.1 (2016 ed.) or Table 10.2.4.2.1 (2019/2022 ed.) apply. That table permits a standard upright sprinkler deflector to be no more than 12 in. (300 mm) below the ceiling or roof deck. Hence the maximum permitted distance is 12 in. (300 mm).

A. 1 in. – This is the minimum allowed distance for uprights under the table, not the maximum.

B. 6 in. – Within the permitted range but not the maximum limit required by the question.

D. 22 in. – 22 in. is allowed only when sprinklers are placed below very deep beams (>12 in.) at the bottom of the beams, not when they are centered in each bay.

1. NFPA 13, Standard for the Installation of Sprinkler Systems, 2016 Edition.

• Table 8.6.4.1.1, “Deflector Distance Below Ceiling for Standard Sprinklers” (p. 93) – shows 1 in. min., 12 in. max.

• 8.6.4.1.2.1(1) (p. 95) – allows sprinklers between beams ≤ 7 ft 6 in apart to follow Table 8.6.4.1.1 limits.

2. NFPA 13, 2019 Edition.

• Table 10.2.4.2.1 (p. 124) – same 1-12 in. limits for standard uprights.

• 10.2.6.1.4(1) (p. 130) – classifies beams ≤ 7 ft 6 in apart as obstructed construction where sprinklers in each bay use Table 10.2.4.2.1 distances.

3. University of Maryland, FPE 623 “Sprinkler System Design,” Lecture 5, slide 12 (Spring 2022) – summarizes NFPA 13 deflector-to-ceiling limits for smooth and closely-spaced beam ceilings.