Installing a Ceiling Fan Box

Use a knife (not a saw) to cut through the drywall or plaster around the old box. The box is probably attached to a joist with screws or two horizontally driven nails. Force the box loose by hammering a 2X4 into it.

Insert a flat pry bar between the box and the joist. Pry the box away from the joist. You may need to pry out a staple anchoring the cable to the joist. Work carefully to avoid unnecessary damage to the ceiling.

Pry out the box's mounting nails and pull the box down from the ceiling. Disconnect the cable from the box. The box shown has a slot that the cable slides through; pry the tab and pull the cable out. If the box has a cable clamp, remove the locknut.

To install a braced box, slip the brace through the hole. Rotate the shaft of the brace clockwise until it touches a joist on either side and its legs rest on top of the drywall or plaster.

Tighten the brace with a wrench or groove-joint pliers. Attach the U-bolt to the brace and slide the box up through it. Tighten the nuts.

If you can get at the attic space above the ceiling box, go there to disconnect the old box. Install a braced box.

Here's an option that eliminates the need for a new box. Screw the fan's mounting bracket directly to a nearby joist. The plate will be off-center, so you may need a medallion to cover the hole.

Older pancake boxes mount with screws driven into a framing member. Remove the screws and pry out the box.

If a box is too firmly mounted to be knocked free, cut a hole into the ceiling just large enough so you can see the mounting nails and the cable. Carefully cut through the nails with a reciprocating saw.

If a strong framing member is positioned directly above the box's hole, a pancake fan box or a box with a joist bracket through its center may be the easiest to install.