How To Install A Ceiling Junction Box For A Light Fixture

21 December 2015
 Categories: , Blog


If you want to install a ceiling light fixture, you need to install an electrical junction box. The electrical junction box joins the wiring, and helps give the fixture support. Though it would seem simpler to just insert the wires through the drywall, a shortcut such as this could result in fires, or cause the fixture to fall along with part of the ceiling. Here are some tips to install an electrical junction box in the ceiling.

Prepare to Install

For this task, you need:

  • stud finder
  • voltage tester
  • tool belt
  • safety glasses
  • work gloves
  • ladder
  • drop cloth
  • pencil or painter's tape
  • electrical cable and connectors
  • 4-inch hole saw and cordless drill
  • center punch
  • mallet
  • junction box

Before you begin, check local building codes to ensure you follow the jurisdiction's wiring guidelines. Lay a drop cloth over the area to catch falling debris from the ceiling. Shut off electricity to the room from the circuit, then test with voltage tester.

Mark Location and Cut a Hole

Locate a joist in the place where you want to install the fixture with the stud finder, preferably in the center of the room.  Wearing work gloves and safety glasses, climb the ladder carrying supplies in the tool belt, mark the position between joists, not on them, with a pencil or painter's tape.  

Lay the box between the marks, and trace around it. Cut a hole in the drywall along the trace marks with a hole saw attached to the drill, and tuck insulation that falls out of the hole.

Attach the Box

Set the brace in the opening with the brace feet sitting on the drywall inside the ceiling. Turn the brace legs to the right until you meet resistance, which indicates they are secure with the joists. Don't make it too tight, or it could damage the ceiling.

Locate wiring from the main breaker or a switch, and run it to where you are installing the box. Place the center punch on one of the holes, also called the knockout, and use the mallet to remove it from the box. Feed the cable through the box, and fasten with a cable lock connector.

Slide the U-shaped bracket over the bar with the bracket ends pointing to the floor. Insert the cable from the hole into the cable lock, then insert the box on the U-shaped bolt, securing it with the provided nuts. Don't connect the cable from the power source until you install the fixture.

Installing an electrical ceiling junction box makes fixtures safer. Working with electricity requires following safety procedures and building codes. If you don't trust your skill, or the fixture doesn't work after installation, contact an electrician.


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