Adding Intermediate Switch

[New2Game]

Just been to house to add 3rd switch to landing light circuit. Thought would be easy simply adding 3core and intermediate switch. But when opened both swicthes up, upstairs and down, both only had 1 wire in each of the 3 terminals, instead of 2 wires in L1 & L2.
How can i add the 3rd switch?
Would putting an intermediate between L1 & L2 of both upstairs and downstairs swicthes work?

 

[fattony]

1 wire at each switch would indicate to me there may be a junction box or wired in singles,I assume you know how to wire 2 way and intermediate switches?

 

[New2Game]

yeah know how to wire two way and intermediate, will i have to find junction box if wanna add 3rd swicth tho?

 

[GaryMo]

Would putting an intermediate between L1 & L2 of both upstairs and downstairs swicthes work?

Yes.