Crossing ceiling joists with lighting cable

[Lobster]

Hi

I'm sure this is an obvious question but... when rewiring the lighting up in the roof space, where should I run the cabling? I was intending to clip it to the sides of the joists whereever possible, just below the top edge, meaning that it won't get damaged by any temporary boards I may put down for access; yet will remain more or less visible and not buried under Rockwool - OK?

How about when I need to cross the joists at 90 deg, though? Or should I just never do that, and always go the long way round, parallel to the joists? (I've never seen that done in any place I've lived, but especially as I'm going to get inspected eventually, I figure I need to do this by the book). If I can cross joists, should it be on fixed supporting battens or something? And presumably above the Rockwool, which isn't in place yet? The current wiring I'm removing crosses joists everywhere, clipped in places so you could put your whole weight on a cable between two joists if you weren't careful.

BTW is it a 'requirement' to physically remove any old cables when you do a rewire?)

Thanks David

[John Rumm]

Sounds good so far....

Normal practice in the loft is to cross them as and when you need. If you are planning to lay boards over the cables then you either need to drill holes in the sides of the joists (probably not worth the hassle), or notch the top of the joists. Personally I did the latter when I boarded my loft a few years ago. A router with a half inch bit is ideal for making small channels in the joists. A handy tip is to mark on the boards where the wires cross so you don't get carried away when screwing/nailing them down.

Nope - joists are usually 400mm or less apart - not a problem span for ordinary T&E cable.

Don't think it is a requirement - especially when you think that many cables might be buried in plaster etc. It would be worth while removing as many as you can without causing much extra work though, simply to avoid the confusion of having lots of extra wires about and not knowing which are live!

[Christian McArdle]

Notching is now frowned upon. Drilling is supposed to be the answer, although ceiling joists may be too thin even to allow proper drilling away from the edges.

Christian.

[Scott M]

In some ways it'd be a good idea to make it a requirement having played in the loft of my new place - picking up a half buried length of cable from the insulation to find you're holding a couple of bare ends while balanced on a joist is always fun.... ;-)

And then there's the length of cable that's dead & disconnected at one end yet still plumbed into a fully connect junction box at the other...

[Lurch]

Sounds fine.

The usual way is to run on the side of the joist to the nearest batten\stringer or whatever crosses the joists at 90 degrees and follow that along to wherever you need the cable to go.

I don't think so, it does make it easier to remove what you can see though. ..

SJW A.C.S. Ltd.