Install a Recessed Light Fixture

Existing ceiling. If you’re putting lights in an existing ceiling, buy remodel can lights, which generally have retractable fasteners that grab the ceiling. If you have less than 8 inches of clearance between the ceiling and the surface above it, buy low-clearance canisters, which are shorter than standard can light fixtures. If there is insulation in the ceiling, buy IC — insulation clearance — canisters, which are designed to keep the insulation from overheating and possibly starting a fire.

New construction. If there’s no drywall on the ceiling yet, buy new-work cans, which nail to the joists.

Can light trim. For each recessed light fixture, you also need a piece of can light trim. These plastic or metal rings snap onto the lights from below to cover the gap between the hole you cut in the ceiling and the edges of the fixture. Trim also gives each light its finished appearance. The rings come in a multitude of styles, so pick a design that matches your home’s decor.

Existing ceiling. Turn off power to any electrical wires you’ll be working with or near, and use a non-contact AC voltage detector to make sure the juice is cut. Use a compass or the templates that come with the remodel can lights to draw a circle on the ceiling for the fixture. Measure to your next fixture location and draw another circle, and so on.

If the ceiling is drywall, poke the point of a drywall saw into the layout line and cut out the hole. If the ceiling plaster and lath, make sure you put on safety glasses before cutting the hole you marked. You can minimize cracking neighboring plaster by scoring along the line with a utility knife first. Then drill a hole just inside the layout line and put the drywall saw or keyhole saw in the hole to start the cut. To prevent the lath from flexing and causing the plaster to crack, carefully put your hand on the ceiling close to the blade as you work.

With any type of ceiling, do not use power saws, which may cut through pipes or wires before you are aware of the presence of those potentially dangerous obstacles.

New construction. Mark the spots on the joists where you want to attach the recessed wall fixtures.

Existing ceiling. If you're not comfortable working with electricity, hire an electrician to run cable to the recessed lights. Running cable from an existing ceiling junction box to a new location is relatively easy, but the job gets messy if you have to drill through joists, which usually run perpendicular to the roof ridge. If a cable has to run through a joist, you have to remove part of the ceiling below the joist to get the drill in position. An experienced electrician can minimize the damage and make sure the rewiring meets building code; although, making the ceiling repairs will still be up to you. Running new cable from a switch is especially complicated and best done by an electrician.

New construction. Running cable yourself is easier when doing new construction, but building code requires you to make every connection inside each junction box easily accessible. When you run cables, leave about 16 inches of wire hanging from the ceiling hole for each light.

Can light fixtures have built-in junction boxes with several holes covered by breakaway plugs called knockouts. You need to remove one of the knockouts on each fixture so you can feed cable wires into its junction box. Choose the knockout that makes connecting wires from the cables to the wires in the fixture easiest. If there’s a slot in the knockout, put a screwdriver in the slot and move the screwdriver back and forth until the plug breaks loose. If there’s no slot, put a screwdriver on the plug and hit the screwdriver with a hammer until the knockout falls out.

Some fixtures have built-in supports that keep the cable away from the sharp edges of the hole created by removing the knockout. Others require you to insert a separate grommet or cable clamp, which isn’t included in the box, to do the job. Follow the directions that come with the fixtures you bought.

Use a cable ripper and a utility knife to remove 6 to 8 inches of the insulating jacket from the outside of the cable running from the ceiling junction box, revealing the separately insulated wires inside. Then strip about 1/2 inch of insulation from each of those wires using wire strippers. Remove the cover from the can light fixture junction box. Feed the cable’s wires through the knockout hole so that the outer insulation just enters the box. Connect all the wires as directed in the instructions that come with the can light fixtures you bought. Generally speaking, you connect white wires to white wires, black wires to black wires, and the bare wire from the cable to a green wire in the fixture. To do so, put the wires to be connected together, put a wire nut over them, and twist to tighten. Wrap the wire nut and wire with tape to keep the nut from twisting off.

When you have attached and secured all the wires, reattach the lid to the fixture junction box.

Existing ceiling. Follow the directions to retract the wings that stick out from the side of the can until they are flush with the side of the can. Slip the fixture into its hole and then extend the wings to hold it in place.

New construction. Nail or screw the fixtures in place, using the marks you made on the joists as guides to placement.

Existing ceiling. Snap the can light trim in place on each recessed light fixture, following the directions that came with the fixtures.

New construction. With new construction, you need to wait until the ceiling is in place before snapping on the can light trim. Mark and cut the holes for the can lights on the drywall before putting it up. Once your ceiling is hung, attach the trim.