I am installing (6) brand new smoke alarms in my home, including running all new 14/3 wire to each alarm. I have purchased "old work" electrical boxes for all of the alarms. However, the existing smoke alarms are installed by just screwing the bracket on to the stud and cutting in a small hole next to the stud to route the wire down.

I know the electrical box would probably be the best method, but it seems the advantages of just mounting to the stud and cutting a small hole would be (a) smaller wall cutout and (b) quicker/easier install time.

So the question is: Should I install smoke alarms in an electrical box or mount them directly to the stud?

1 Answer 1


A proper electrical box is the only way to do this. You CANNOT simply cut a hole and pass the wires through. Any and all line voltage (120/240V and up) splices must be in an approved box and be accessible, meaning you cannot bury a junction or splice box. I could cite all sorts of relevant codes but I don't think that's necessary. This should be obvious.

Here is a recent thread on this very subject: What type of electrical box do I use for a hard-wired smoke detector?

Remember, it is almost a certainty (code wise in the US) that an AFCI breaker is required.

  • I did see the related thread, and I already knew that the answer was probably that I should install it with an electrical box. Obviously whoever installed the existing alarms was being lazy like I was tempted to be, but I will be adding the electrical boxes.
    – StephenH
    Commented Jan 8, 2016 at 16:13
  • 1
    @StephenH, very good. Glad you are going the proper way. .................. Yes, we in the trade see this all the time and it makes me furious that folks would cut corners like this. The stuff we see buried in walls would make you cringe. Commented Jan 8, 2016 at 16:15
  • I was already leaning this way. I've worked hard to do all modifications on my house using best practices/adhering to any and all code. I'm planning on routing the new 14/3 wire in the attic and running it to a new separate 15A breaker. I know it's overkill, but I figured the safest bet was to have it on its own circuit.
    – StephenH
    Commented Jan 8, 2016 at 16:18
  • See recent edit regarding AFCI breaker Commented Jan 8, 2016 at 16:19
  • Thanks for the tip. I knew I DIDN'T want to have it on a GFCI breaker because you don't want critical devices on a circuit that could trip.
    – StephenH
    Commented Jan 8, 2016 at 16:21

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