Codes Re: Openings in Fire Rated Walls

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harp2005

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Does anyone know the various NEC codes which limit the area of openings in a fire-rated wall? For instance, there can't be more than xx square inches of opening per 100 square feet of wall.

I was told that an electrical box (even a steel one with a steel cover plate) is considered an opening in the fire-rated wall system. There are also limitations or prohibitions to having electrical boxes opening to opposite sides of the wall within a certain horizontal distance (usually in the same stud bay).

Thanks
 
Re: Codes Re: Openings in Fire Rated Walls

the code your looking for is in the nfpa book on "fire ratings" --- it covers drywall thicknesses and allowable openings within wall surface areas...
 
Re: Codes Re: Openings in Fire Rated Walls

there are too many different applications to be posted here, even if one was very dilligent. A typical steel framed one hour wall has restrictions that are different than a garage/house hybrid seperation. If boxes cannot be mounted such that they are in different bays, they can be isolated before closing in with sheetrock by individually rocking them.

these details are often very well defined on the plans, or referenced by a listing.

house seperations are somewhat mitigated by the individual jurisdictions, some jurisdictions being more stringent than others.

paul
 
Re: Codes Re: Openings in Fire Rated Walls

From Volume One of the UL Fire Resistance Directory.

WALL AND PARTITION ASSEMBLIES

Metallic Eletrical Outlet Boxes

Listed single and double gang metallic outlet and switch boxes with metallic or nonmetalliccover plates may be used in bearing and nonbearing wood stud and steel stud walls with ratings not exceeding 2h. These walls shall have gypsum wallboard facings similar to those shown in Design Nos. U301,U411, and U425. The metallic outlet or switch boxes shall be securely fastened to the studs and the opening in the wallboard facing shall 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 shall not exceed 16 sq in. The aggregate surface area of the boxes shall not exceed 100 sq in per 100 sq ft of wall surface.

Metallic boxes located on opposite sides of walls or partitions shall be seperated by a minimum horizontal distance of 24in. This minimum seperation distance between metallic boxes may be reduced when "Wall Opening Protective Materials" (CLIV) are installed according to the requirements of their Classification.

Metallic boxes shall not be installed on opposite side of walls or partitions of staggered stud construction unless "Wall Opening Protective Materials" are installed according to the requirements of their Classification.

Roger

[ January 25, 2005, 03:26 PM: Message edited by: roger ]
 
Re: Codes Re: Openings in Fire Rated Walls

Thanks Roger. I've asked about every architect I know about that and none of them really knew for sure.

What about panelboards in a rated wall?? I think we have specified that before with the panelboard boxed in with an extra layer of sheet rock.

Also, what about smoke partitions? Do 4 square boxes affect the integerity of smoke partitions?

Steve
 
Re: Codes Re: Openings in Fire Rated Walls

Steve, you're welcome. You are correct that panelboards must be "five sided" (in otherwords the membrane must be continuous around the can) due to their physical size (greater than 16 sq "), and putty patches are not listed for this use. :)

Roger

[ January 25, 2005, 06:53 PM: Message edited by: roger ]
 
Re: Codes Re: Openings in Fire Rated Walls

Thank you all for your replies and time.

Roger,
Does the same rule apply to plastic boxes?
Here's my situation:
I recently had a severe electrical fire in my finished garage. As a repair my electrician cut and spliced wires into 16 sporadically placed single junction boxes in my 13x20 garage ceiling, which is located directly below my bedroom. These plastic junction boxes must be accessible to meet NEC code 314.29. May all these juction box openings be a fire code violation?
 
Re: Codes Re: Openings in Fire Rated Walls

Harp, if you are who I think you are, I must say you are determined. If not, don't take it personal. :D

Plastic boxes are allowed in 1 and 2 hour walls with the same stipulations put on metalic boxes.

I would suggest you visit UL's website and search for plastic electrical boxes.

BTW, the UL website is not the easiest website to use.

Roger

[ January 25, 2005, 08:34 PM: Message edited by: roger ]
 
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