On Sunday, November 17, 2019 at 7:25:07 PM UTC-5, Ken wrote:
Jake Chominsky wrote:
I have an 1950s home with older wiring. Most of the house only has a black
and white wire connecting to lights and recepticals.Â* I want to do a 3-way
switch. Currently, the power is coming in through the light then
connecting to
the on/off switch. How could I install a 3-way if I can only add a new
wired
line from a new switch (#2) to the current light and also cannot upgrade or
touch the existing wired line from the current switch to the current the
current light? The reason I cannot touch the existing line is because it is
behind 2x4s and walls whered I have to demo a wall which is outside of my
capabilities.
Look at:

https://www.do-it-yourself-help.com/...-diagrams.html

+1

His case is the "light first" one. A three wire cable to the new location and two 3 way switches will do it. The only issue is code compliance, since there is no ground on the circuit. I guess you're either supposed to rewire the whole circuit or get an inspector that says it is ok to expand this without being compliant. It would be no less safe than what's already there.