Install a Ceiling Light and Switch

Step 2: Cut Box Holes

After ensuring that you have an accessible supply of electricity, follow these steps:

1. Locate the switch and light boxes. If possible, plan to fasten boxes to studs or joists (the ceiling beams). Find the studs and joists, which are usually 16" apart, by tapping on the wall or ceiling. Drill a small hole to confirm the location; the drill bit should hit wood in the stud or joist.

2. Cut access holes in the upper wall and ceiling, about 5" square, avoiding the framing. Square or rectangular holes are easier to patch. Likewise, separate holes, as already shown, are easier to repair than one big hole that meets at the ceiling corner.

3. Locate the light box. Generally, octagonal boxes are used for ceiling lights. Hold the box against the ceiling, mark the opening, and then cut.

To mount a light in the ceiling, and connect it to a wall switch, I cut four holes: one each for the switch and light boxes, and two for routing cable. Think of these as fishing holes.

Measure the height of an electrical switch in the room. Place the bottom of the new box at the same height. Using a level, mark the new switch box cutout on the wall. (If you can't mount the box alongside a stud, buy a box designed to grab drywall; these are convenient but weaker.)

To start the saw blade, drill a ³⁄₈" hole at each corner. Also drill for the switch-mounting screws at center top and bottom.

A jigsaw makes a fine instrument for cutting a box opening in plaster or drywall. Run a variable-speed jigsaw slowly to control dust. An extra-short blade will preserve cables already in the wall.

Step 3: Fishing the Wire Through the Wall

With the box holes cut, turn your attention to electrical cable. If you are working on a 15-amp circuit (check the fuse or circuit breaker), use 14-gauge wire. Use 12-gauge wire for a 20-amp circuit. First drill holes to run the cable, and then pull cable between the box openings.

Drilling for Cable

Extra-long drill bits are essential for drilling these holes, and I advise using an 18"-long bit, ³⁄₄" in diameter from the start. In the example, you will drill only one hole, up through the plate, the framing on top of the studs, at a steep angle. In other situations, you might have to drill sideways through studs; the technique is similar to what's shown here.