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#153711 - 11/04/03 08:28 PM cut-in boxes  
gunther  Offline
Joined: Sep 2003
Posts: 60
Thought I had posted this but I never saw it come up so forgive me if it turns out this is double posting.
About a year or so ago, in our area, all of a sudden the inspectors came down with it was no longer acceptable to use cut-in boxes in fire walls. Their objection was to the box support clips, you know the kind that are called steamboats or madison clips or F-clips. I checked the code and it says that approved boxes are ok to use but doesn't address whether the box supports are acceptable or not. The cut-in boxes themselves come with ul lablels on them but I don't see any on the clip and I assume they are designed to be used with those types of boxes.
It has been a little confusing because some inspectors are only saying that they are banned in certain hour rated walls (five? i think and not three hour?)
On existing fire walls we have been going to locating the stud and cutting in a four square to mount on it and making it a quad in order to not have any patch work.
Can anyone shed any light on why the inspectors all of a sudden came down with this and what is your opinion about it?

Building Codes & Related References

#153712 - 11/04/03 08:38 PM Re: cut-in boxes  
Roger  Offline
Joined: May 2002
Posts: 1,716
Gunther, I don't have it here at home but this goes back to the UL Fire Resistance Directory. (Orange Book Set)

In short, "cut in boxes" and even " some plastic boxes" are approved for rated walls up to two hour if secured to a stud. I will post the exact wording tomorrow.

Actually, all boxes used in rated walls must be supported by framing or structure.


[This message has been edited by Roger (edited 11-04-2003).]

#153713 - 11/05/03 06:00 AM Re: cut-in boxes  
gunther  Offline
Joined: Sep 2003
Posts: 60
When you say "all boxes" I am taking it that that includes the ones cut in for fire alarms and telephones also.

#153714 - 11/05/03 06:37 AM Re: cut-in boxes  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Wow that will be a messy job.

Figuring you will have two layers of sheet rock and that the seems can not be on top of each other.

I have never heard of this requirement, for fire walls we are told not to put boxes in the same stud bay on opposite sides of the wall.

Is that a requirement or just "we have always done it that way"?

Bob Badger
Construction & Maintenance Electrician

#153715 - 11/05/03 04:44 PM Re: cut-in boxes  
gunther  Offline
Joined: Sep 2003
Posts: 60
Our inspectors enforce that you cannot have a box on the opposite side of the fire wall within 24" on the horizontal (vertical distance not considered). So you better check before you cut-in around here. The only exception in new walls is that you can surround your box with a "putty patch" that is made out of fire rated material and completely seals the box off or you can frame and sheetrock around the box in the wall.

#153716 - 11/05/03 07:15 PM Re: cut-in boxes  
Ryan_J  Offline
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
2000 IBC states that (711.3.3)
Membrane penetrations shall comply with Section 711.3.1. Where walls and partitions are required to have a minimum 1-hour fire resistance rating, recessed fixtures shall be installed such that the required fire resistance will not be reduced.

1. Steel electrical boxes that do not exceed 16 square inches in area provided the total of such openings does not exceed 100 Square inches for any 100 square feet of wall area. Outlet boxes on opposite sides of the wall shall be seperated as follows:

1.1 By a horizontal distance of not less than 24";

1.2 By a horizontal distance of not less than the depth of the wall cavity where the cavity is filled with cellulose loose fill or mineral fiber insulation;

1.3 By solid fire blocking in accordance with Section 716.2.1; or

1.4 By other listed materials or methods.

Ryan Jackson,
Salt Lake City

#153717 - 11/05/03 07:39 PM Re: cut-in boxes  
Roger  Offline
Joined: May 2002
Posts: 1,716
From Volume One of the UL Fire Resistance Directory.


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.


#153718 - 11/05/03 09:59 PM Re: cut-in boxes  
Joe Tedesco  Offline
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
300.21 Spread of Fire or Products of Combustion.

FPN: Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made.

Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance–rated wall assembly. An example is the 600-mm (24-in.) minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall.

Assistance in complying with 300.21 can be found in building codes, fire resistance directories, and product listings.

Joe Tedesco, NEC Consultant

#153719 - 04/26/04 05:48 PM Re: cut-in boxes  
richard  Offline
Joined: Aug 2003
Posts: 95
L.I. New York
so how would you put a one gang box in, if the location could not be next to the stud? do you rip the wall open and frame it out? or do you use madison clips?

#153720 - 04/27/04 12:20 PM Re: cut-in boxes  
Roger  Offline
Joined: May 2002
Posts: 1,716
Richard, as far as a rated wall is concerned, madison straps won't do.

This is actualy where the rumor starts every now and then that madison straps are illegal.

They are not allowed for rated assemblies, so the only option is to find a way to fasten to a stud or to a part of the structure.


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