Running cables across from joist to joist

[Nemo2000]

The lights on my stairs are controlled by pair of switches - one at top, one at bottom - connected by 3core&earth for 2-way switching. As part of some refurbishment work I have relocated the upstairs switch and now need to reroute the 3&E cable (actually, I'm going to disconnect the old cable and run a new length). The new route will pass under a bedroom floor at right-angles to the joints. As the O/D of the new cable is approx 10mm I have drilled new 12mm holes in each joist (on the joist centre-line)ready to thread my new cable across.

But....should the cable have any additional support between joists? The joists are at approximately 16" centres, so the approx 14" gap between joists exceeds the recommended 300mm spacing used when doing horizontal clipping. I could drop the cable down to the ceiling and run across the plasterboard and back up again between each joist, but then I'm worried about what might happen in the future if anyone ever drilled into the ceiling from below in order to fix something. Looking around under the flooring with a torch, there appear to be other cables run across through joists without any support.

I can't find anything in any specific guidance which seems to address this issue, only the need for protection from screwing into floorboards from above. From what I have read elsewhere on this forum the answer appears to be that simply suspending the cable should be OK, but it would be nice to get confirmation

Thanks!

 

[thomp1983]

Worrying about nothing, make sure it's pulled reasonably tight and then clip it to the joists when it runs parallel to them and that should keep it in place for the next 50 years or more

 

[Nemo2000]

Thanks!

 

[EFLImpudence]

Whilst there are no rules whether the cable should be tight or loose; being loose might mean it is more likely to be pushed out of the way should a drill encounter it, there are rules regarding where the holes in joists may be drilled.

Cutting notches and drilling holes in joists

As part of any new installation work or a re-wire, a cable, trunking or cable tray sometimes has to pass through an element of building construction, such as a floor, wall or beam, necessitating the formation of a notch or opening in the element. To comply with Regulation 522.8.14, no wiring...

electricalapprentice.co.uk