How to Finish a Basement Bathroom – Part 15

How to Finish a Basement Bathroom – install the old work electrical box and wire vanity light switch.

This project is continued from How to Finish a Basement Bathroom – Part 14.

Vanity Light Switch Electrical Wiring

The new run of NM-B 14/2 electrical cable was fished through the wall in the previous project update and is hanging out of the hole sawn in the drywall for the old work electrical box:

Bathroom Light Switch Wiring: NM-B 14/2 Cable Rough-in

Bathroom Light Switch Wiring: NM-B 14/2 Cable Rough-in

A single NM 14/2 cable is used to wire the single pole light switch. The neutral (white) wire is recoded as hot by coloring the end black with a felt tip marker per the bathroom wiring diagram because it serves as a hot wire in this light switch application:

Light Switch Wiring: White (Neutral) Wire Recoded in Black for Hot

Light Switch Wiring: White (Neutral) Wire Recoded in Black for Hot

The NM-B 14/2 cable is inserted through the back of the old work electrical box then the light switch is side-wired:

Side Wiring the Light Switch

Side Wiring the Light Switch

Needle nose pliers are used form a hook in the ground wire to connect the light switch ground screw:

Light Switch Wiring: Ground Wire

Light Switch Wiring: Ground Wire

The ground wire is hooked around the light switch ground screw:

Light Switch Wiring: Ground Screw and Wire

Light Switch Wiring: Ground Screw and Wire

Use the needle nose pliers to close the ground around the ground screw, then tighten the ground screw:

Light Switch Ground Wiring

Light Switch Ground Wiring

The light switch wiring connections are complete. The single pole light switch makes/breaks the hot wire circuit which is the reason for recoding the white neutral wire as black for hot:

Single Pole Light Switch Wiring: Neutral Wire Recoded as Hot

Single Pole Light Switch Wiring: Neutral Wire Recoded as Hot

The old work electrical box and light switch is ready to be mounted in the drywall. I’ve extended old work box swing-clamps to illustrate how these automatically rotate and grab the interior wall when the mounting screws are tightened:

Basement Bathroom Wiring: Old Work Junction Box and Light Switch

Basement Bathroom Wiring: Old Work Junction Box and Light Switch

Close the swing-clamps closed and insert the old work switch box into the wall. Tighten the two mounting screws until the swing-clamps and drawn against the drywall, but don’t over tighten or you’ll crush the drywall.

Notice which end of the light switch is marked TOP or UP on back and reorient the switch if needed. Fold the wires in the switch box and fasten the switch mounting screws. Attach the face plates to the GFCI electrical outlet and vanity light switch.

Light Switch Wiring: Old Work Electrical Box and Single Pole Switch

Light Switch Wiring: Old Work Electrical Box and Single Pole Switch

The basement bathroom switches and outlets are labeled here for clarity:

Basement Bathroom Light Switches and GFCI Electrical Outlet

Basement Bathroom Light Switches and GFCI Electrical Outlet

The old work electrical box and vanity light are installed in How to Finish a Basement Bathroom – Part 16.

Take care,

Bob Jackson

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