Weird wiring at switch and light

I'm trying to add a new outside light just outside my back door with using power from a current switch box and it is powered from the ceiling light currently in place. Now the weird part. It is old fiber sheathed wire that comes into the switch box. I thought the power came from the light 1st because there is only 1 set of wires that comes into the switch box and just to check i opened up the light box and only found one set of wires in there to which I assumed there would be 2 / sets (1for power in and 1 to go onto the switch). I want to put a combo switch in , 1 to run the current light and the other to run the new outside light. How do I wire this up? I know which wire is hot in the switch box but have not been able to get past that with assurance that I can wire it correctly. Is a combo switch the way to go or should I just make it 2 separate switches in a bigger box?

 

Both the ceiling box and the switch box one have one cable? Does the wiring have a ground?

 

So what you're saying is that the switch only has one wire in there with presumably a black and white conductor and a light with also one wire (black and white also)?

 

There is no ground and both the ceiling and switch boxes have only 2 wires coming into it presumably 1 blk and 1 white each. I have found the hot in the switch box.

 

Then there should be two cables but you said there was only one? You didn't use a non contact tester did you? If you did and have only one cable the result is false.

 

I Used a multimeter to determine which wire was hot.

 

There is 2 wires in each box

 

You have a switch loop. The hot you detected in the switch box is the hot leg coming from the ceiling box.

You do not have a neutral in the switch box and cannot feed power to the new light from the switch box.

 

Ok thank you , now can you explain how power got to the light with only 2 wires coming into that.

 

That is part of the problem. You seem to be missing at least one cable.

An ungrounded circuit should not be extended.

 

There is probably a mystery box you haven't found. Power comes into that box then one cable goes to the light and one cable goes to the switch. Your meter was measuring voltage through the bulb.

No ground wire means you are dead in the water anyway. A circuit with no ground can't be used because code requires all new circuits must be grounded. Are there any properly grounded receptacles near where you want the porch light?