I'm trying to run a new AC circuit to a bedroom above my unfinished garage. I'm using metal clad romex ( flexible conduit ) to save time and make it easier to accomplish. Access to the breaker panel is on the wall outside of my garage. So what I'm doing is running the MC romex, exposed, across the top of my garage and then penetrating near the base of the wall in the second floor bedroom. I consulted an electrician who told me that it's not against code to run the MC romex through the garage in this manner, so that's not the issue I'm concerned with.

What I am concerned with is where the mc romex goes through the penetration through the drywall from the unfinished garage. I'm using this little breakout box as strain relief, but it doesn't seem right. My understand is that by code I need to use a bushing to secure the mc romex in the knockout hole, but what about at the drywall penetration.

Is there a bushing I should be using there?

Should I not be running mc romex through the inside of the wall in the first place?

(There's just something about this that looks off).

enter image description here

penetration far off

  • Something like these. I am sure an electrician will give an educated answer. lowes.com/pd/… - lowes.com/pd/…
    – Alaska Man
    Commented Apr 25, 2021 at 21:41
  • 1
    Just eliminate the box, fire-tape the drywall hole.. Commented Apr 25, 2021 at 21:52
  • @NoSparksPlease - there are these cupped Ls that screw into the drywall to handle the hole and keep line from moving. I have a bunch of these I got from restore but not sure what they are called. I used 2-3 for garages and makes things look nicer - especially if things are painted.
    – DMoore
    Commented Apr 25, 2021 at 22:01
  • @DMoore You wouldn't have picture you could post by any chance, would you?
    – Frank
    Commented Apr 25, 2021 at 22:17
  • I agree with not using a box @nosparksplease+ I am curious about using a conduit body in that location or that is what I would consider L’s / LL, LB, LR conduit body’s i haven’t seen anything like that used do you have an example?
    – Ed Beal
    Commented Apr 25, 2021 at 22:36

2 Answers 2


It does indeed "look off" because you don't simply run the MC or MC-lite cable through the box. You need appropriate clamps, and the clamps need the jacket cut on the armored cable, and then you have wire nuts in the junction box (because you also have to cut the wires to get the clamps in place.)

Armored cable is fine in drywall - indeed, it's superior to NM cable, and required in many/most commercial occupancies if not using conduit.

  • OK. I do plan to install clamps on horidonal entry point, But it's what to do in the drywall penetration part that I'm confused about. So should I cut the cable in the box, wirenut them together, and then clamp the armor at the hole that's flush with the drywall? Then not worry about bushings in the drywall penetration?
    – Frank
    Commented Apr 26, 2021 at 1:04
  • Remove the box from the drywall. Install a clamp properly to the cable and box where the cable goes into the drywall. Attach the box to the drywall with the cable properly clamped.
    – Ecnerwal
    Commented Apr 26, 2021 at 12:42

MC is a wireway much like flex, rigid or pvc, if fire block is required it will need to be sealed like any other wireway.

As this a garage if it is attached to the residence it will need to be sealed there is a fire stop red foam that meets code for residential sealing or other listed fire stop sealers.

If a detached garage no sealing may even be required, I usually cut the hole at an angle so the mc or flex lays flat on the ceiling in a case like yours and continue with anchors, in the case of electric water heaters I come out at a 90 and mud around the flex.

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