Even if you used the QR reduction, and you got the design area down to 900 sq. If you want to sprinkle between every truss (sprinklers spaced at 16" intervals!!) be my guest. I can agree that words alone are hard to interpret.
Composite wood joist fire sprinkler design area incrase plus#
Running through the widest open space, you'll be 8" horizontally from each truss, plus the diagonal distance from any member. If the truss is 18" deep as you state, call out your branchline el. design area comes into play for combustible concealed spaces, refer to Section 11.2.3.1.4 in the 2010 edition of NFPA 13.
Where wood joist or composite wood joist construction is used in ceilings not attached directly. However, the fitter will hang the line through the opening in the truss, so your measurement would be taken diagonally from the nearest member. One way they can do that is to omit sprinklers from areas where the. o.c., double top plates, single bottom plate. Framing - Nominal 2x4 wood studs, spaced 16 in. By looking at a plan view of a 16" OC truss layout, then no, you couldn't get 10.5" away. FIRE-RATED WOOD-FRAME WALL AND FLOOR/CEILING ASSEMBLIES 5 WS4-1.1 One Hour Fire-Resistive Wood-Frame Wall Assembly 2x4 Wood Stud Wall 100 Design Load ASTM E 119/NFPA 251. If they were 24" OC, would you not be 12" from each truss, measured to the centerline of the head, if the head is centered between the trusses? RE: Open web wood trusses carlosgw (Mechanical) Of course, the above is my interpretation, and I may be corrected by some of the more knowledgeable members. Is the 2x4 deeper than the height of the triangle? The depth of the 2x4 member is what you now take into consideration.
You've stated that the webs are made of 2x4's. Your least dimension would be the shortest side of the triangle (likely the "height"). To answer your latest question, think of it this way: The opening in the truss are going to be triangular. If the openings are less than 70% - Obstructed. Unobstructed construction has horizontal members that are not solid, where the openings are at least 70 percent of the cross-section area and the depth of the member does not exceed the least dimension of the openings, or all contstruction types where the spacing of the structural members exceeds 7 1/2'. N3.7.2 Unobstructed Construction: Construction where beams, trusses or other members do not impede heat flow or water distribution in a manner that materially affects the ability of a sprinkler to control or suppress a fire.
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