Obstructions Against the Wall “I am trying to apply figure A.8.6.5.1.2 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 foot 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.8.6.5.1.2 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, 2010 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 8.5.3.2.3 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 8.6.5.1.1 indicates that sprinklers shall be located so as to minimize obstructions to discharge as defined in 8.6.5.2 and 8.6.5.3, or additional sprinklers shall be provided to ensure adequate coverage of the hazard. Since the obstruction is located 20 in. below the deflector, 8.6.5.3.1 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 8.6.5.3.3. Hence, Figure A.8.6.5.1.2 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. 8.6.5.2.1.2 would refer back to 8.6.5.1.2. Applying 8.6.5.1.2(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. ========= Technical Update is prepared by the Technical Services Dept. of the AFSA: Roland Huggins, a PE registered in fire protection engineering, Vice President of Engineering and Technical Services; and Tom Wellen, a PE registered in fire protection engineering and Tom Noble E.T., a Technical Programs Specialist. This is provided with the understanding that the AFSA assumes no liability for this opinion or actions taken on it and they are not to be considered the official position of the NFPA or its technical committees. Copyright 2017, American Fire Sprinkler Association. All Rights Reserved. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.firesprinkler.org/private.cgi/sprinklernotes-firesprinkler.org/attachments/20170417/1d392eed/attachment.htm>
