Device Boxes in Fire Rated Walls (Putty Pads)

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richc516

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Does anybody have a clear understanding of this rule? We are doing a large project in NYC and have most of the building roughed. The GC is now telling is that some of the boxes in fire rated walls require putty pads. I have seen the code (NFPA maybe?) that describes that a box that is over 16 square inches (which applies, in some cases we used oversized boxes), a 100 square foot area, etc, etc and I have also seen literature from STI, Hilti and 3M on this. What is strange to me is that this has never come up on our projects before, by a building or electrical inspector. Another thing I cannot understand is does this rule apply to the size of the box or the opening in the sheetrock wall. We mostly use single gang adapters. Also, steel boxes have a two hour fire rating, so shouldn't that be sufficient enough and basically be part of the two hour fire rated wall? I might not be doing a great job of describing this, but if anyone can shed some light on the subject, it would be appreciated.

Thanks
 
richc516 said:
Also, steel boxes have a two hour fire rating, so shouldn't that be sufficient enough and basically be part of the two hour fire rated wall?
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From the UL White Book:

6. Metallic Electrical Outlet Boxes
Listed single and double gang metallic outlet and switch boxes with
metallic or nonmetallic cover plates may be used in bearing and nonbearing
wood stud and steel stud walls with ratings not exceeding 2 h. These
walls should have gypsum wallboard facings similar to those shown in
Design Nos. U301, U411 and U425. The metallic outlet or switch boxes
should be securely fastened to the studs and the opening in the wallboard
facing should be cut so that the clearance between the box and the wallboard
does not exceed 1/8 in. The surface area of individual metallic outlet
or switch boxes should not exceed 16 sq in. The aggregate surface area
of the boxes should not exceed 100 sq in. per 100 sq ft of wall surface. The
aggregate surface area of the boxes may be exceeded when Wall Opening
Protective Materials (CLIV) are installed according to the requirements of
their Classification.
Metallic boxes located on opposite sides of walls or partitions should be
separated by a minimum horizontal distance of 24 in. This minimum
separation distance between metallic boxes may be reduced when Wall
Opening Protective Materials (CLIV) are installed according to the requirements
of their Classification.
Metallic boxes should not be installed on opposite side of walls or partitions
of staggered stud construction unless Wall Opening Protective Materials
are installed with the metallic boxes in accordance with Classification
requirements for the protective materials.
 
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