Using a cut-in box in a common wall.

Discussion in 'Electrical Forum discussion & Blog' started by solidworks400, Feb 19, 2012.

  1. solidworks400

    solidworks400 New Member

    Messages:
    3
    Location:
    Rockford, IL
    I am in the process of adding an interior bedroom to my townhouse. One of the walls is a common wall and fire rated with two sheets of 5/8" drywall. Where I live Romex is code and not conduit. To minimize the cutting into of an existing wall, I want to use cut-in boxes. Is it within code to use these on a fire rated wall or do I have to attach a box directly to a stud?

    Chris
  2. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    the box itself must be rated.
  3. solidworks400

    solidworks400 New Member

    Messages:
    3
    Location:
    Rockford, IL
    Rated in terms of what? And as to my original question, can I use this type of box?
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Interesting question , as I have sensed in recent years that inspectors are very touchy about fire walls.
    When dlarivee says the box must be rated....it is true that any pentration in a fire rated door or wall, the device must carry a UL Fire Rating. If it is a fire rated door, the jamb and the door knob hardware must be rated. An entry door which opens to a fire rated hallway, the door, the lockset, and THE VIEWER, if there is one, MUST be UL rated. If you recess a fire extingquisher cabinet into a fire rated wall, a regular steel cabinet is NOT enough. It must be a fire rated cabinet, which will actually have an additional steel liner of minimum thickness. get the picture??

    I don't know what it takes for an electrical box to be fire rated. Someone will tell us.
  5. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    You're creating a penetration in a fire rated wall, why do you think there aren't already a bunch of holes in this wall?
  6. solidworks400

    solidworks400 New Member

    Messages:
    3
    Location:
    Rockford, IL
    I don't understand your response. A metal box would be fire rated, so is this box within code to use.
  7. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    So you're sure you have UL listed boxes and that you're following the requirements of a fire rated assembly within the wall?
  8. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
  9. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Thank you for that reference. Here is a partial quote from it:

    The metallic outlet or switch boxes must be securely fastened to the studs. Openings in the wallboard facing are to be cut so that the clearance between the box and wallboard does not exceed 1/8 inch. The surface area of individual metallic outlet or switch boxes must not exceed 16 square inches. In addition, the entire surface area of the boxes must not exceed
    100 square inches per 100 square feet of wall surface.

    A minimum horizontal distance of 24 inches must separate metallic boxes located on opposite sides of walls or partitions. This minimum horizontal spacing may be reduced through the use of UL Classified Wall Opening Protective Materials (QCSN), commonly known as “putty pads” or “insert pads.” Further, metallic boxes cannot be installed on opposite sides of walls or partitions in staggered stud constructions unless putty pads or insert pads are installed with the metallic boxes in accordance with the Classification requirements for the protective materials.


    With that information, you can determine if what you are proposing is compliant.l
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