Firewall 3-hr

[Mslacat]

Sorry if this is bone head question but it has been a while since I have to use a firewall to seperate buildings. I have a single level storage facility project. A metal building supplier is providing the all metal storage buildings. I am designing a wood frame building that one of the storage building abut into. The wood frame structure (1-story Type V-non-rated) is 1200 sqft office (B occupancy) and 2000 sq ft. of storage (S1 occupancy). The metal storage building (assumed Type II -S1 occupancy)will abut the S-1 occupancy of the wood frame building. I need to seperate the two structures, with a fire wall becuase the total sq ftg exceeds 9000 sq ft.. IBC Table 706.4 indicates that the firewall needs to have a 3-hr rating. There is no water to this site so sprinkling is not an option. I do not see any exceptions or footnotes that would change the 3-hr rating.

Agree so far?

The owner/contractor would prefer to frame the wall in wood studs. I ran into this problem about 8 years ago it does not seem much has changed. I can not find a rated 3-hr wood stud assembly in the UL listing nor GA-600 manual. I find metal studs & cmu assemblies. I find in a UL document BXUV.U419 a discussion how 3 layer of 1/2" or 5/8" gyp board ea. side will give you a 3-hr rating but no actual assembly is listed. Can anyone point me in the direction of a 3-HR wood stud assembly or am I barking up the wrong tree. Framing up a metal stud fire wall is a fall back or is there another solution I am missing. Thank folks in advance.

 

[classicT]

Well, part of your struggle is going to be finding an assembly that is self supporting and structurally independent. Due to this requirement, most fire walls will be either constructed with the shaft-liner panels and the melt-away aluminum clips, or CMU walls. I do not believe that you will find a wood frame assembly that can be used as a fire wall.

706.2 Structural Stability
Fire walls shall be designed and constructed to allow collapse of the structure on either side without collapse of the wall under fire conditions. Fire walls designed and constructed in accordance with NFPA 221 shall be deemed to comply with this section.

Exception: In Seismic Design Categories D through F, where double fire walls are used in accordance with NFPA 221, floor and roof sheathing not exceeding 3/4 inch (19.05 mm) thickness shall be permitted to be continuous through the wall assemblies of light frame construction.​

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706.3 Materials
Fire walls shall be of any approved noncombustible materials.

Exception: Buildings of Type V construction.​

 

[mtlogcabin]

Have you looked at 506.3 and applied any area factor increase based on frontage?. Classify the entire building as a V-B, no separations required between the S-1 and B occupancies