Electrical – Install fire/smoke alarm directly to stud or in electrical box


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?

Best Answer

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.