Routing 2.5mm TAE through floor joists

[padstar]

What size diameter hole should 2.5mm twin and earth be routed through floor joists via and are they best to be cut centrally from top to bottom?

 

[EFLImpudence]

2.5mm² T&E is just under 11mm wide. Yes, hole in the centre of the joist.

There are also rules about the lateral positions.
https://www.diynot.com/wiki/Electrics:route

 

[sparkwright]

You may be able to use a slightly bigger hole if it's likely more cables will be added, but a 16mm hole will be fine for one 2.5mm2 T+E.

 

[padstar]

Thanks. I will work to the guidelines. So a 16mm hole for single pass and 20mm for 2 cables? Is clipping cables to joists when running parallel with them a requirement or just good practice?

 

[EFLImpudence]

Not a requirement. Not usually possible.