Remote Area for Composite Wood Joist Channels
╥We have had multiple AHJs determine the intent of whether or not this concealed combustible space with composite wood joists requires a 3,000 sq. ft. calculation area. Section 8.15.1.2.6 references equivalent materials to the web construction and Section 11.2.3.1.4(4)(j) does not. The annex A.11.2.3.1.4(4)(j) also refers to gypsum or equivalent material used as the fire stopping. Is it the intent to apply the 3,000 sq. ft. remote area when applying Section 8.15.1.2.6?╙ We have reviewed NFPA 13, 2013 edition that you indicated as the applicable standard. Our informal interpretation is that gypsum should be added to the composite wood joist channels to limit the volumes to less than 160 cu. ft. to avoid a 3000 sq. ft. remote area. Chapter 8 and Chapter 11 have two separate functions regarding sprinklers. Chapter 8 determines when sprinklers can be omitted in concealed combustible spaces. Chapter 11 sets the minimum remote area size based on the arrangement of concealed combustible spaces. Section 11.2.3.1.4(4)(j) states, ╥Light or ordinary hazard occupancies where noncombustible or limited combustible ceilings are attached to the bottom of composite wood joists either directly or onto metal channels not exceeding 1 in. in depth, provided the adjacent joist channels are firestopped into volumes not exceeding 160 cu. ft. using materials equivalent to 1/2 in. gypsum board and at least 3 1/2 in. of batt insulation is installed at the bottom of the joist channels when the ceiling is attached utilizing metal channels.╙ Additional guidance is provided in the annex as A.11.2.3.1.4(4)(j) that indicates gypsum board (or equivalent material) used as the firestopping will compartmentalize the concealed space and restrict the ability for fire to spread beyond 160 cu. ft. zones covering multiple joist channels. This is different from Chapter 8 where sprinklers can be omitted from the concealed combustible space. Chapter 11 has the requirement for gypsum in order to avoid the 3,000 sq. ft. remote area. The reason for the gypsum to be added is that the composite wood joist webs fail so quickly during a fire. The gypsum enclosure may be one or multiple composite wood joist channels depending on the construction configuration. A 3,000 sq. ft. remote area will be required if gypsum or equivalent is not installed to limit the volume to 160 cu. ft. With the overall concealed space subdivided by gypsum into 160 cu.ft. portions, this now presents a risk similar to the long-standing allowance in 11.2.3.1.4(4)(d)that divides the overall space into 160 cu. ft. portions using solid wood joists. ------------ 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. 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 2016, 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/20160516/31f34cbd/attachment.htm>
