I have a basement stairwell with 3-way switches (at the top and bottom of the stairs) and a light at the bottom of the stairs.

Each switch only has a single 12-3 Romex cable, and the light has two 12-2 Romex cables. (I'm not sure where power is entering the equation, or how each component is connected to the others). There must also be another junction box where one or more of these lead to.

My goal is to add a wall sconce at the top of the stairs, somehow connected off of "Switch B". Is this possible?

Current Wiring

  • 1
    Can't be done with those switches - you don't (currently) have neutral in either of the boxes. If you're willing to upgrade to 'smart' switches, then you probably can rewire things to support what you want to do.
    – brhans
    Jan 15, 2022 at 1:22

1 Answer 1


You have to come off the existing light.

A light needs 2 wires: switched-hot (red here) and neutral (white). That is always available at the lamp.

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Sometimes it is available at one of the 3-way switches, but that will be only true at a 3-way switch in certain possible topologies, none of which exist if you only have one /3 cable to each switch.

It might be possible if the circuit can be fully documented (where do those red wires go?) and the routing is favorable to applying smart switches. Smart switches remove the need for 2 travelers, liberating wires for other uses.

  • I ended up finding the junction box that was connected each of the components. Unfortunately, it did not contain a neutral wire, but I was able to run a neutral from a nearby lightbulb (on the same circuit). I then rewired things to install a standard smart switch at Switch B (top of the stairs, along with the new sconce). I then disconnected Switch A (bottom of stairs) and replaced it with another smart switch that just tells Switch B to turn on/off.
    – Chris Voth
    Jan 23, 2022 at 20:04

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