How to Cut in an Electrical Box (with Router) through Drywall

Cutting in an Electrical Box (Router Method)

Most professional drywallers cut electrical box openings with a router. You'll be pleasantly surprised how quickly you can develop a feel for the process.

Practice with the new tool before you commit to a full sheet of drywall. Temporarily screw a piece of scrap drywall over an electrical box, then cut the opening. Shift the drywall to a new position, and keep trying until you become confident of your new skills.

To control the dust, purchase a dust hood accessory for your router. Hook it to your shop vac. The fine dust can quickly choke your vac, so clean the filter often.

Checklist

Time
With even a little experience, you'll cut an electrical box opening in less than one minute.

Tools
Drywall router with piloted bit

Skills
Operating a router

Prep
Mark the location of electrical boxes on the floor; shove wiring to the back of the box.

Materials
The usual set of tools needed for hanging drywall

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Step 1

Chuck a piloted drywall bit into the router, and set the tool on a piece of drywall so that the bit overhangs the edge. Loosen the depth-of-cut adjustment knob, and set the bit so that it will cut about 1/8 inch deeper than the drywall's thickness. Securely lock this setting.

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Step 2

Shove the wiring as far back as possible in the electrical box. Hang the sheet of drywall, but keep all fasteners about 16 inches away from the box so the wallboard won't crack when you make the cut. Mark the approximate centerpoint of the box and plunge the running bit at this mark.

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How Do I Control the Dust?

Drywall routers have high-speed motors that excel at two things: fast cutting and kicking up clouds of dust. Fortunately some drywall routers offer a dust hood as an optional accessory. When you connect the chute of the hood to a 1-1/4-inch shop vac hose, you have an effective dust-collection system.

Several cautions are in order. First, be sure to wear hearing protection when you operate this system. The combination of the shop vac and router produces a noise level that's deafening. Second, clean the shop vac filter regularly to maintain maximum efficiency.

Step 3

Move the router to your right until you feel the bit contact the edge of the box. Tip the router slightly backward as you continue to move the tool about 1/4 inch to the right. This move jumps the bit over the edge of the electrical box. Return the router to its perpendicular position, and slide it slightly left until you feel the bit touch the outside of the box.

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Step 4

Move the tool counterclockwise around the perimeter of the electrical box, keeping the bit in constant light contact with the box. When you complete the cut, withdraw the bit and shut off the tool. Set it down where the bit can't strike anything while it coasts to a stop.

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Another Way to Mark a Box

Here's another way to mark the location of an electrical box. It has extreme accuracy, but it requires you to remove the drywall to cut the opening.

Smear a thin coating of powdered chalk on the face of the outlet box. Position the drywall in its exact installed position, then firmly tap the drywall with your fist to transfer the chalk to the back of the panel. Remove the drywall panel, and place it face down on sawhorses.

You may need to trace the perimeter of the chalk mark with a pencil to make it easier to see. Cut the opening with a jab saw, cutting one blade width to the outside of the line. Replace the panel on the wall, and fasten it.

Step 5

If you need to make the opening bigger, you can easily see where to cut. You can use the drywall router or jab saw to make the adjustment.

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Protect the Wiring

Switch boxes are often at the seam line of drywall that's applied horizontally. While that makes the box opening easy to cut, it also means that the wires can get encased in joint compound when you tape and mud the joint.

To avoid a messy cleanup chore, shove all the wires as far back into the box as possible. Then cut a piece of corrugated cardboard to fit snugly into the box, and jam it into place. Leave the cardboard in position through all the finishing and painting steps. When you pop out the protective layer to install the switches, the wires will be clean.

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