Membrane Penetrations

[RJH333]

I have a metal stud wall with 4 inch square metal boxes on both sides on a demising wall in a residential application.
I asked the Fire inspector if I could putty pad the boxes that are with-in 24 inches. I have back to back kitchens and can not separate all of the outlets more that 24 inches.
He said because the wall is metal stud it is communicating and every box on both sides of the wall would have to be protected or the wall would have to be insulated with mineral wool. He is looking at IBC 713.3.2. He stated that the holes in the metal stud make it a communicating wall. There is a resilent channel on one side which would keep the rock off of the studs for sound reasons, and this would also allow heat and smoke to travel. This is the first time I am hearing of this we would always just putty pad the boxes with in 24 inches and be done. Anyone?

 

[mwm1752]

I am responding with certain assumptions
You are working with a designed & tested rated wall assembly
The wall is specific per design
IMO you are protecting the penetration of the wall as if there was no penetrations
The requirement to protect penetrations are defined in 2009 IBC 713.3.2
2009 IBC 713.3.2 does not reference the assembly design used.
The AHJ (which is usually the building dept is construction situations) does have control but I would ask for code specific articles for future references.
Sounds like your Fire Marshall has adopted the IBC for his inspections or he could be a Combination Inspector with proper certification.

 

[cowboyjwc]

Metal or wood shouldn't matter. You have many times where the wall is 6", but it's built with off set 2x4's and of course almost all commercial is metal framed.

So in answer to your question, yes fire pads may be used instead of off setting the boxes, but your fire pads must also have the correct sound rating also. IBC 712.3.2.1.2.

Also remember that it's a horizontal distance, it doesn't matter if one box is 6' above the other, still need a fire pad.

Oops, sound transmission is a CA code, sorry.