Question:
I've framed around some ductwork in my basement with 2x2's which has lowered the ceiling height about a foot in some places. Problem is, there is a smoke detector attached to the ceiling joist right where I had to drop the ceiling. I obviously can't box in my smoke detector, but there isn't enough electrical cable to bring it down the needed foot to the new ceiling height. I can't extend the cable because I can't leave a concealed mid air splice. So what do I do? Can I surround the splice in an electrical box? But that would also be concealed in the ceiling, and I thought you couldn't conceal electrical boxes behind walls and ceilings? The cable goes up through the house and powers smoke detectors on the two floors above, so pulling it all out and fishing down new cable is pretty much out of the question.

Answer: You can not bury a box in a wall or ceiling, unless you leave some sort of access. My last ditch effort would be to mount a electical box and detector on the cover of a plastic access panel, run a short wire up to the old box, and spice it in. The old box will be accessable by removing the cover, and should meet code. You can buy 14" x 14" plastic access covers in most any home store.