Repairing a broken screw hole on a plastic junction ceiling box?

Question

One of the screw holes on a junction box on my ceiling has fallen apart, leaving a hole that is too big to fix a screw into (see top of picture). As a result, I cannot hang my smoke detector from the junction box, since the detector hangs from the heads of the screws.

I was trying to see if there was something I could fill the hole with to then make a new hole for the screw. This would save me the cost and hassle of having the box replaced, which I assume would require cutting into the ceiling (the box seems to be affixed to a brace above the ceiling that runs between two joists, since all I see is the head of a bolt at the top of the box and no nail heads anywhere). Any thoughts on what I could do here?

Thanks

longneck · Answer

That box is a type of plastic called Bakelite. It's tough, but brittle. If you're careful, you can break the box apart without damaging the ceiling. If you have a hole saw, you can probably drill out around the rivet heads you see in the back of the box and it will come right out.

Then you can replace it with a new "old work" box.

Iggy · Answer

Yep, you can fill it by tightly stuffing it with even just damp toilet paper, paper towel or napkin(s), then let fully dry and harden...a liberal coating of Krazy Glue on the first wad would help.

Otherwise, a wood putty or auto body (car) dent filler (Bondo) would likely be a more permanent solution for future smoke detectors. If you can drill small holes through the sides, then the insert of a nail or brad for the filler to stuff around will really help durability.

isherwood · Answer

I'd just use a toggle bolt. No need to patch or replace the box if the outer shell is intact.

Repairing a broken screw hole on a plastic junction ceiling box?

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