Dear Mr. Electrician: Is it possible to install an additional dimmer next to an existing one and connect a new ceiling light to the new dimmer?

Answer: Yes. However the methods used to achieve this type of installation will vary according to your building structure and the location of the switches and light fixtures.  Below are photos of a simple dimmer and ceiling light installation in a two story condominium.  Text links go to applicable products on Amazon.com

Light and Dimmer Switch Installed in an Existing Wall

This was the existing diva dimmer switch for ceiling lights in the adjacent room
This was the existing Diva dimmer switch for ceiling lights in the adjacent room.

You need to determine where you will be getting power from and where do you want the wall switch to be located.  In the example on this page I was lucky to find power in an existing wall switch where the client wanted the additional switch located.  Not all wall switches have a hot and a neutral.  Some just have a hot and a switch leg which cannot be used to feed something else.

The existing dimmer switch box had the correct wiring in it to facilitate the connection to another light fixture
The existing dimmer switch box had the correct wiring in it to facilitate the connection to another light fixture

I used a long thin screwdriver inserted along side of the switch box to feel for any obstacles such as pipes or wood studs.  A short piece of fish tape can also be used for probing into a wall.

I removed the existing one gang plastic switch box and cut a hole for a new two gang plastic old work switch box.

Hole for new two gang switch box is ready
Hole for new two gang switch box is ready

The existing black switch leg wire was temporarily identified with green electrical tape.  The other black wires get spliced together.  The wood stud on the left side of this wall opening is perfect for attaching the new two gang plastic old work electrical box for additional support.

The access holes in the wall and the ceiling to facilitate the installation of a new wire to feed the new light fixture
The access holes in the wall and the ceiling to facilitate the installation of a new wire to feed the new light fixture

The access hole in the wall and the access hole in the ceiling were made using “The Grabowski Method” (Hold the Saw at a 45 degree angle) to facilitate the installation of a new wire to feed the new light fixture. A large hole is needed to fit the Milwaukee right angle drill into the wall to drill up into the top support plate.

I did have to cut holes in the ceiling and the wall to facilitate the installation of a new 14/2 Romex cable to the new light fixture location.  I cut the holes at a 45 degree angle inward to make it easy for patching later.

Access hole cut at 45 degree angle
Access hole cut at 45 degree angle

This hole was made using “The Grabowski Method” of cutting holes in drywall. You simply hold your compass saw at a forty five degree angle inward when cutting to give you a beveled edge. This makes it much easier to patch the hole using the same piece of cut out drywall and some joint compound. Lately I have been using my Milwaukee Cordless Multi-Oscillating Tool to cut such holes.

View inside the wall of a drilled hole going through the top plate of the wall
View inside the wall of a drilled hole going through the top plate of the wall

The above view is the inside of the wall through the hole in the previous photo.  The big hole in the wall was needed to accommodate the big angle drill and a long auger drill bit.

I had to drill a hole using my angle drill to penetrate the top supporting plate in the wall to get the new Romex cable into the ceiling.

Hole in ceiling for new electrical box
Hole in ceiling for new electrical box

The hole above is for the new octagonal electrical box that will support the light fixture where the customer wanted it.  The existing cables in the ceiling are set back far enough to provide clearance for the new box.  You can see the side of the laminated beam on the bottom edge of the hole.

A view inside the ceiling shows wires penetrating the laminate beam
A view inside the ceiling shows wires penetrating the laminate beam

Because this ceiling was supported by trusses instead of solid wood joists I was able to get my fish tape through very easily after the holes were made.

Two fish tapes have been pushed in and are ready for the wire to be attached
Two fish tapes have been pushed in and are ready for the wire to be attached

I have several pieces of short fish tape which had broken off of my longer fish tapes.  The short fish tapes come in handy for small jobs like this.

Fish tapes are ready for the wire to be attached and pulled into the ceiling and wall holes
Fish tapes are ready for the wire to be attached and pulled into the ceiling and wall holes
Wire is still attached to the fish tape after being pulled in
Wire is still attached to the fish tape after being pulled in
View inside the ceiling with the new wire pulled through the hole in the laminated beam
View inside the ceiling with the new wire pulled through the hole in the laminated beam
A 4 inch diameter by 2-1/8-Inch depth octagonal side mounted to a ceiling joist
A 4 inch diameter by 2-1/8-Inch depth octagonal side mounted to a ceiling joist

The fender washer allows for a little adjustment to get the box positioned correctly. The other screws lock it in place.  Note the copper ground wire attached with a 10/32 screw.

In most cases I would have used a fan rated ceiling box and installed a 14/3 cable for future fan use.  However this light fixture installation was in a small nook next to the dining room.  It was not likely that a ceiling fan would ever be wanted there.

The light fixture hook and bracket are attached to the deep octagon electrical box in the ceiling
The light fixture hook and bracket are attached to the deep octagon electrical box in the ceiling.

Everything metal must be grounded.  Because I used a metal box and grounded it, the round fixture mounting bracket is grounded by being physically attached to the ceiling box.  If the ceiling box was plastic it would have been necessary to install a ground wire onto the green screw on the mounting bracket.  The light fixture ground wire will connect to the ground wire in the ceiling electrical box.

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