I have a metal box and conduit outlet in my kitchen where a bar cabinet is going to be installed. I assume it would be way too much effort to rip out plaster and move the box to a new location, so I would rather just have the outlet inside of the bar for lighting purposes. Would I just need a metal extender for the box to extend the outlet into the back of cabinet? I assume non-metallic plastic extender is no good.

2 Answers 2


The National Electrical Code does not allow devices to sit back inside combustible material.

The pertinent article attention to the second paragraph:

314.20 Flush-Mounted Installations. Installations within or behind a surface of concrete, tile, gypsum, plaster, or other noncombustible material, including boxes employing a flush-type cover or faceplate, shall be made so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1∕4 in.).

Installations within a surface of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall extend to the finished surface or project therefrom.

They make cheap box extensions that are basically a piece of stamped metal with a slit in one side that can be installed without de-terminating the device. Just remove the receptacle, slip the conductors through the slit in the side and reinstall it flush with the surface.

Good luck!

  • In trying to understand this answer, I would like to ask about my similar situation. In renovating our kitchen we placed a cabinet over an existing wall receptacle. I had the cabinet installers cut a rectangular hole in the back of the cabinet to expose the box, and I was planning to use a plastic extender to allow the duplex receptacle to be screwed to the extender and allow the cover plate to fit flush with the back of the cabinet. To use the receptacle I would have to open the cabinet, and plug in a cord. Right now we have the breaker to that box turned off, and the wires are capped. Jan 10, 2018 at 19:20
  • @JimStewart That sounds good. What was your question?
    – ArchonOSX
    Jan 10, 2018 at 19:54
  • My situation sounds like the situation with the poster here. So he can use the box extender, right? Since his box is metal and may be part of the grounding path, then he might have to use a grounding pigtail. Jan 10, 2018 at 22:42
  • Yes, and yes. As long as the receptacle is bonded with a pigtail to the equipment ground you are good. The extender just serves as a barrier between the receptacle and the combustible material.
    – ArchonOSX
    Jan 11, 2018 at 9:45
  • In regard to this section of the code is ordinary drywall "non-combustible"? What I am wondering about is that I see a lot of cases (including my house) where the fronts of the boxes were installed flush with the studs. I can't see how this could pass inspection. I thought it was an absolute requirement that the boxes be positioned so that the front would be flush with the drywall! How could this practice be allowed to continue?! When we moved in every one of our receptacles was springy! If I were a home inspector, I would flag this. I had to install either shims or box extenders. #$@%!! Jan 11, 2018 at 12:33

Why not just cut a hole in the cabinet? One advantage to doing it this way is the plugs end up farther back, therefore taking up less space inside the cabinet.

  • Are you advocating cutting a hole in the back of the cabinet larger than the cover plate so that the receptacle and its cover plate would be against the original drywall and so would be recessed from the back of the cabinet? The one problem I could see with this is that in the case of a fixed cabinet (such as a kitchen under-counter cabinet) this would allow access of critters into the cabinet and small objects might be liable to falling into the space between the cabinet and the wall. Jan 11, 2018 at 13:13

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