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Building Codes and Inspections/1-Hour Occupancy separation in Type V


We need to build a 1-HR partition to separate a medical suite from neighboring suites, so, floor slab-to-wood-deck (one-story building with hip roof). The building is a Type-V with combustible wood stud partitions and wood web trusses. Where we cross the wood truss webbing with our separation, the existing trusses will penetrate the layers of 5/8" gypsum board, etc. Do we need to do anything more than to gyp around the trusses at their penetrations through the wall, and caulk the annular openings, or would there be another requirement for sealing or separating the 2 sides?
Chuck G

The short answer is that you can't do it. But, it depends. Generally speaking, you can't penetrate a rated assembly with wood floor trusses, because it defeats the required purpose of a noncombustible barrier because the wood will burn out, allowing the fire and smoke to pass the barrier. A rated wall pieced around trusses is not a rated assembly. You can use a different listed rated assembly, there are many.  The Underwriters Laboratories website can gain you access to some.

A better approach might be to use other design alternatives if possible to eliminate the requirement for the rated assembly.  In the mixed use section of the ICC International Building Code (IBC), one can sometimes design the entire building to the most restrictive use, and if the area does not exceed the allowable area for the construction type, then the otherwise required mixed use separation may not be needed.  Sprinklering the building also negates some rated assembly requirements.  You might be able to provide a one hour rating to the underside of the wood truss floor/ceiling assembly (the ceiling), then run the rated fire partition up to the underside of the rated ceiling. Sometimes the tenants want a substantial assembly for security reasons.  Sometimes a landlord wants tenants separated to limit fire or smoke damage when the building code does not require it. They don't want a burnt coffee pot or trash can fire causing thousands of dollars damage in multiple tenant spaces.

I suggest you contact the Building Official of the municipality to see what edition of what code is law, and see if there are any local amendments to the law. Building Codes are not the same everywhere. Then the options that the code allows can be evaluated so you can determine the most cost effective way to comply with the building code.  This is precisely the function of the design professional (architect).  

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Keith Fuller


I'm an ICC Certified Master Code Professional fielding general building code questions. My experience has been heavy in fire related issues.


I've been employed since 1985 as an inspector and plan reviewer, and am a municipal Assistant Building Official and Deputy fire Marshal. I've had fire service experience since 1972, having served as a three time Fire Chief and Fire Marshal in years past. The increasing workload, mandatory certifications, and continuing education requirements in recent years have caused me to concentrate my efforts on code related issues. I hold national fire service certifications as well.

ICC Master Code Professional

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