How do I convert a light circuit with a single pole switch to use two 3-way switches?

Question

I have a box in the hall which includes a 3-way switch (with another switch at the other end of the hall), a single pole switch to the garage lights and a single pole switch to the exterior lights on the garage. The single pole switch to the garage is wired with a 3 wire plus ground. The white and black wires feed the garage lights from the switch and the red wire feeds the garage ceiling outlets and is hot all the time.

In the garage I would like to add a 3-way switch for the garage lights and another 3-way switch for the exterior garage lights. In other words I would like to be able to turn on both of those light locations from both the inside hall and the garage as well. I know that I will of course have to replace the existing single pole switches in the hall with 3-way switches and add a junction box in the garage with 2 3-way switches in it. The thing that I don't know is what wiring connections I need to make.

Can you help?

Answer 1

Since the red wire is already being used for the outlets, you'll need to run a pair of 3 wire cables from the existing switch box to the location in the garage where you want these light switches.

This is what you'll likely have to do:

Here are some other options:

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