sprinklernotes
Obstructions Against the Wall “I am trying to apply figure A.10.2.7.1.2 to a bulkhead with a demising wall above it stepped back about 8 in. from the front edge of the bulkhead. Below the bulkhead is a floor to bulkhead wall that is stepped back 2 ft-8 in. from the front edge of the bulkhead. Two feet of the depth below the bulkhead is filled with a full height built-in cabinet. The AHJ is not comfortable allowing this code to be applied in my situation because the wall is not in the same vertical plane above and below the bulkhead. I do not see any dimensions in figure A.10.2.7.1.2 that give a depth of the setback for the wall. The figure only gives a maximum depth of 4 ft. I am well under this total width and my sprinkler head is 20 in. above the top of the bulkhead. Can I apply this code to avoid installing a sprinkler in the 8-in. wide bulkhead in front of the cabinet?”
We have reviewed NFPA 13, Standard for the Installation of Sprinkler Systems, 2019 edition that you indicated as the applicable standard. Our informal interpretation is that a sprinkler is not required in the 8-in. bulkhead. A cabinet fills the void where an 8-in. shelf against the wall is present. The standard does reference in section 9.5.3.2.2 that the distance from the wall to the sprinkler shall be measured to the wall behind furniture, such as wardrobes, cabinets, and trophy cases. That is to address the correct placement of the sprinkler. What the standard does not say is to omit this cabinet when considering obstructions. As such, the cabinet becomes the face of the wall when applying the obstruction rules. This should not be considered as a 2 ft-8 in. niche. This application is an 8-in. shelf against the wall. Section 10.2.7.1.1 indicates that sprinklers shall be located so as to minimize obstructions to discharge as defined in sections 10.2.7.2 and 10.2.7.3, or additional sprinklers shall be provided to ensure adequate coverage of the hazard. Since the obstruction is located 20 in. below the deflector, section 10.2.7.3.1 would apply. More specifically, sprinklers shall be installed under fixed obstructions over 4-ft wide, such as ducts, decks, open grate flooring, cutting tables, and overhead doors per section 10.2.7.3.2. Hence, figure A.10.2.7.1.2 specifically shows your application. The vertical plane above and below the obstruction doesn’t appear to be of a concern for this application as both surfaces will be wetted. If, for instance, the distance from the deflector to the shelf was less than or equal to 18 in., section 10.2.7.2.1.2 would refer back to section 10.2.7.1.2. Applying section 10.2.7.1.2(3), nicknamed the soffit rule, this would place the sprinkler a minimum of 20 in. away from the obstruction to the centerline of the sprinkler. The sprinkler is located at 24 in., thus you met the intent of the standard.
