Expert: Nazim Nice - 3/24/2010

Question
Hi,
Thank you for considering my question.

Re. a 2-story commercial post and beam building constructed in the 1940's.. We'd like to change the use of the 1st floor from storage to A-3, and one of the requirements is a 2-hour fire separation between the 1st and 2nd floors. The floor-ceiling configuration between the two floors are: 4x13 solid wood beams 32" on center, 2x6 tongue-and-groove car decking, and 1/2" plywood with carpet. I have not been able to find a 2-hour fire rated assembly to confirm this, but the design we are considering is 20 ga furring channel 24"oc, with two layers of 5/8 Type X drywall at right angles, separated by Resilient channel. My question is: How do I go about getting this approved? Or do you have an alternative idea/design?

Thanks so much!
~Hendrik
Seattle, WA

Answer
Hi Hendrik,

I think you'll have to try and find the closest assembly you can and see if the building department will buy that it will perform closely enough to the tested assembly.  

With the 2 layers of 5/8" GWB, my first question is there a requirement to protect the actual structure from collapse if there is a fire above?  How is an assembly like this going to protect the A-3 occupancy if the fire is in the storage above?

Also, you may want to check on the change of use triggering other structural & seismic upgrades to the building.  An A-3 occupancy has quite different requirements than a storage use.

Nazim Nice
Principal / Architect
http://www.motion-space.com
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