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How to Install a New Ceiling Box in an Existing Ceiling

Chris Deziel

Since the electrical code requires all wire connections to be made in an electrical box, installing a box in the ceiling is a necessary precursor to hanging a new light fixture. Drywall doesn't hold screws, so the box serves a dual function by supporting the weight of fixture. If the ceiling is already covered over, installing a remodeling box to hang a lightweight fixture will save time and effort. To hang a heavier fixture like a chandelier, however, you must attach a rough-in box to a rafter. If you can't work in the attic, this may mean cutting away drywall.

Installing a Remodeling Box

The electrical code requires installing an electrical box before hanging a ceiling light.
  1. Draw the outline of the back of a circular remodeling electrical box, sometimes called an old-work box, where you plan to put the fixture. It should be located between a pair of rafters, and there should be no framing behind the box.

  2. Cut around the outline with a drywall saw to make a hole. Feed the electrical circuit cable through the hole and into the back of the electrical box through one of the self-clamping holes. Pull enough cable through the box to make connections.

  3. Push the box into the hole until the front edge is flush with the surface of the drywall. Push in the screws on the front of the box with a screwdriver and turn them to engage the anchors behind the box with the back of the drywall. When the anchors are engaged, tighten the screws to hold the box firmly in place.

Installing a Rough-In Box

  1. Work from the attic, if possible. Place a circular rough-in box on the back of the drywall next to a rafter with the back of the box facing you and draw the outline of the front of the box. Cut around the outline with a drywall saw.

  2. Place the box in the hole and adjust it so the front edge is flush with surface of the ceiling. Screw it to the rafter with 1-1/2-inch drywall screws, or pound in the nails that come attached to the box with a hammer. Feed the circuit cable through the back of the box and, if the box has a clamp, tighten it with a screwdriver to hold the cable securely.

  3. Find a rafter by tapping on the ceiling, if you can't work in the attic, and mark its position. Find the edge of the rafter by poking through the drywall with a small nail and mark its position. Place a rough-in box on the drywall with the back facing you so that one edge is on the edge of the rafter and draw its outline.

  4. Draw a rectangle about one foot wide that extends from the center of the rafter to the center of an adjacent one. The outline for the box should be centered in the rectangle and on one end of it. Cut out the rectangle carefully with a drywall saw and clean the edges of the hole and the cut-out piece of drywall by scraping them with a utility knife. Cut around the outline of the electrical box to make a hole for it.

  5. Measure the position of the center of the hole from one edge of the rectangle with a tape measure and mark this position on the rafter. Place the rough-in box on the mark, adjust it so its edge is flush with the ceiling, and nail or screw it to the rafter.

  6. Replace the cut-out piece of drywall and screw it to the rafter on either end with 1-1/2-inch drywall screws. Spread drywall joint compound around the edges of the rectangle with a 4-inch drywall blade, then lay tape on the edges and scrape the excess joint compound off with the blade to flatten the tape. Let the compound dry, then finish off the drywall repair with one or two topcoats of joint compound.