We have a standard two switched system serving a sitting room. We have demolished a small wall to extend the room into a lobby which has one single switched light. I want to connect this light to the two switched system but I don't want to damage the ceilings. One of the switches is adjacent to the 'lobby' and I thought that by connecting in a junction box I could take the live return from the switch to the existing light (having removed the existing switch circuit). As the existing single light is adjacent to a joist I can run a new cable from the jbox to it and use the existing neutral feed.
A junction box with screws or similar connections must be accessible. A proper cable joint with soldered or crimped connections and shrink sleeve or resin incapulation is allowed to be hidden. The switch is unlikely to have a neutral connection and you are therefore unlikely to be able to make a connection there. Because of the way power from one lamp is taken to the next you may be lucky if you lobby is end of line. Lighting is by far the biggest problem for DIY if you read these pages look at the projects page where pictures show how they are wired. In view of how many people get it wrong you may be better with an electrician don't forget Part P if you have building work I expect you already have a building inspector so you will likely need inspection and testing done. Again look at projects and follow links.
Thanks for the info. Fortunately I can place the proposed junction box out of sight but accessible. The neutral feed would be the one serving the existing lobby light. I thought that if that light is the end of feed then no great problem. If not I would remove the existing switched live cable, link up the incoming and out going live on the existing ceiling rose and connect the new switched live through the rose to the lamp as normal (i.e. just use the new switched live and the neutral serving the existing lamp.)
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