If you're adding wires or a bigger device to an electrical box, you may need additional capacity. There are two ways to enlarge an existing box without tearing the wall open.
Remove the old switch (power off) and screw the extender box on top of the old box. Then install the new switch and cover plate on the extension box.
Disconnect the old switch and label all the wires (power off). Saw out the old box, remove the wires and set in a deep remodeling box. Reconnect the wires and install the new switch.
Although your current electrical “box fill” may meet code, it’s not safe to jam a new device in if the box is already full of wires. You have two options: Add a plastic surface-mount extender box (like Leviton No. 6197-W; available through our affiliation with amazon.com; Photo 1), or remove the old 12.5-cu.-in. box and replace it with a flush-mount 20-cu.-in. box that’s 7/8 in. deeper (Photo 2).
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.