Dear Mr. Electrician: How do I repair a ceiling electrical box? I removed the hanging ceiling light fixture in my kitchen and found that the ceiling light electrical box appears to be very loose. Since my new light fixture weighs 18 pounds (double the old fixture) I am nervous about replacing it. The existing ceiling light electrical box seems to be mounted on one side to a joist or something, which I cannot see. Any suggestions?
Answer: If it is a metal box, you may be able to strengthen its support by drilling a couple of screws through the side of the box and into the joist. The box may have been originally installed using nails into the side of the joist. They could have pulled out a little. I have encountered electrical boxes that were fastened to joists using only cable staples. Staples tend to pull out easier than nails. NOTE: Text links below go to applicable products on Amazon or EBay.
If the ceiling box is plastic, I would just remove it and install a metal box. Plastic boxes can be made of different materials such as PVC, fiberglass, or a composite material. Fiberglass boxes can be broken apart as can the boxes made of composite material. PVC boxes do not break apart that easily unless they are old and brittle.
Usually I start with a small pry bar or a large screwdriver and try to get behind the box to force it away from the wood joist. See below about labeling wires first before doing this. At some point after prying I take my Knipex 10″ High Leverage Diagonal Pliers and nip away pieces of the box until I can get it out of the ceiling. Take good care of the wires when doing this.
REPAIRING A LOOSE CEILING ELECTRICAL BOX
Turn the power off to this circuit. Remove the fixture mounting bracket by taking out the 8-32 screws holding it in. Without disconnecting the wires that are inside of the ceiling light electrical box, pull them down and away from the sides of the box.
Drill 2 or 3 holes using a 1/4″ or 3/16″ drill bit through the side of the box close to the ceiling joist. DO NOT drill into the joist. Screw some #10 or #12 long sheet metal screws with fender washers through the holes into the joist.
I’m not sure what screw length you will need but you want to have at least 1″ of screw in the wood. Probably 1 1/2″ or 2″ screws would work. I recommend using hex head or Phillips pan head screws and a drill or impact driver to drive the screws in.
If the existing ceiling box is plastic and it appears broken, replacement is your only option. Use an old work ceiling fan box and brace for replacement.
CEILING FAN BOX INSTALLATION
The alternative to the above repair is to remove the box entirely and install a ceiling fan brace and box which will provide plenty of support. Since the box is loose already, you may be able to pry it away from the joist completely using a small pry bar or a very large screwdriver.
Before you begin to remove the existing ceiling light electrical box, you must tag the wires so that they can be reconnected together properly. You can use colored electrical tape or labels with numbers for this. You must undo any electrical wire splices and then loosen the clamps or remove the locknuts on connectors and remove them from the box.
Next, twist the box around until you are able to pull it through the existing hole without doing too much damage to the ceiling. Buy a fan brace and box kit for retrofit and follow the instructions for installation.
There is a side mount fan box and bracket available in addition to a fan brace that expands between joists. If the joist is right at the edge of the ceiling hole, I suggest the side mount bracket. If the hole is further away from the joist, use the expanding fan brace.
The retrofit expanding fan brace fits up inside the existing hole in the ceiling and you tighten it to lock between two joists. Then the fan rated electrical box gets mounted to the brace with the included hardware. Bring your wires into the new fan box before attaching it to the the fan brace in the ceiling.
You would also use the above technique to install a ceiling fan as that will require the use of a fan brace and box. See my post here about ceiling fans and the fan boxes.
My post about replacing an old style pancake box may be helpful to you.
My post about wiring diagrams for ceiling lights and switches may be helpful.