Do I need to cut into my drywall to install a switch?

Question

I'm looking to put a light in outside my house. The light is going to be positioned directly behind the outlet I have pictured below where the wires are sticking out. I want the switch to control power to this light:

I suspect it to be using this kind of gang box:

I think I need to:

1. Hit one of the knockouts in the gang box out either in the top or bottom of the box.
2. Drill a hole in the 2x4 to get the switch where I need it.

I want to do this with cutting out as little drywall as possible. Can I do this without cutting out all of the dry wall between the switch and the outlet? If so, how do I removed the gang box to remove one of the knock outs?

Answer 1

You're going to have to do drywall repair if you move this switch.

So since you HAVE to do drywall repair regardless, why shy away from doing it the right way?

Cut away a big enough piece of drywall so that you have full access to the existing box, the space where the new box will be, and keep cutting right and left until you hit the bordering studs on either side.

Do your electrical work.

Cut 1 piece of drywall to fit the huge gaping hole you made. Cut out space for your new box.

Cut pieces of 1x2 to fit vertically on the insides of the left and right studs, and to fit across the tops and bottoms of the opening. (6 pieces total)

Install the vertical pieces parallel to the studs with 1" side facing you, so you have a screw edge. Install the horizontal pieces so that the 2" side is facing you and half of it is behind the existing drywall. Screw it in place in the existing drywall.

Take your cut piece of drywall and mount it on the 6 1x2"s you just installed.

Tape and mud - 3 coats - fill coat, feather, final.

Answer 2

If I understand what you have in mind, the light will not be in the room pictured but on the other side of this wall. Only the switch will be on this side.

The outlet box in the first picture (holding the wires) cannot be buried in the wall without access. If you use that box, it need to have a plate on the room side, even if that plate is a blank.

That outlet box already in the wall is more likely one like this

In most buildings wired in the past 50 years, the wires are non-metalic (NM), that is, the outside insulation is a plastic sheath, rather than a metal cover.

These wires are held in by a clamp. The box you picture with the knockouts is used with metal covered wires or wires inside metal conduit (although there is an adapter clamp available for NM cables).

You will need to install a box on the outer wall to attach the light fixture to. You need to make sure that box is watertight once the fixture is installed.

You probably are better off loosening the clamps that hold the wire in, removing the existing box, rerouting the wire from that box to the new box for the fixture and running another set of wires from the switch box to the new box. Remember that no wire connections can be outside a box or inaccessible.

Unless you want the switch exactly where you have pictured it, you could use the old box for the switch and place the new box slightly higher or to the side of the old box, but on the same side of the stud. When you loosen the wire clamp, you may be able to reach the much smaller knockout which can usually be removed with a screwdriver. Then you can leave the power wire in the old box and run a new cable for the switched wire and the neutral and ground from the old box to the new box.

You must make sure that all wires you are approaching are not live. After opening the breaker, test every wire with a non-contact tester, such as this one.

Answer 3

If it is allowed in your area - and different areas have different codes - I would use an "old work" plastic box; you just cut a hole of the proper size in the drywall, and put the box in.