cables through joists

[dunjenkeepa]

Can anyone guide me on the regulations for running cables through joists? I'm installing cable for a lighting circuit and ring main, my electrician just said don't drill too many holes (!) but he wasn't specific about any regulations - eg. distance from pipes, distance from walls etc ?

He is a busy man so I don't want to pester him too much . . .

Thanks

DK

 

[ricicle]

Speak to him again and ask him where the holes should be drilled in the joists - after all his name will be on the certificate. Any decent Electrician will not mind you asking if he has permitted you to do some of the preparatory work.

 

[echoes]

In a nutshell:

Drill through centre of joist.
Max hole diameter is 0.25 joist depth.
Holes at least 50mm from top or bottom of joist.
Leave 3 hole diameters between adjacent holes.
Don't drill close to ends of the joist span (within 0.025 span length)

Keep cables runs a sensible distance from pipes so they (the cables) won't get affected by heat - i.e. not right next to/underneath and certainly not on top

 

[Chri5]

If the existing holes are in a safe area away from other services you can reuse them.

Logic being that it is better to re use holes rather than leaving the joists looking like

 

[ban-all-sheds]

I prefer this Swiss cheese anyway....

http://en.wikipedia.org/wiki/Appenzeller_(cheese)

 

[dunjenkeepa]

can i put both cables eg ring main and lighting through same hole in joist, or should each cable have it's own hole ??

 

[Chri5]

can i put both cables eg ring main and lighting through same hole in joist, or should each cable have it's own hole ??

Yes, but try not to have too many- google "grouping factor" for reasons.

 

[TicklyT]

Have a look through http://www.eastdevon.gov.uk/bc-guidancenote7-notchingofjoists.pdf
It shows the areas where you can notch, where you can drill, and what should keep the building inspectors happy.

 

[Taylortwocities]

can i put both cables eg ring main and lighting through same hole in joist, or should each cable have it's own hole ??

Yes, but cables carrying mains voltages should not share the same hole as services like telephone, networking, TV etc. There should be a separation of at least 50mm (IIRC)/ Reg is (I think) 528.1.

 

[mbga9pgf]

can i put both cables eg ring main and lighting through same hole in joist, or should each cable have it's own hole ??

Yes, but cables carrying mains voltages should not share the same hole as services like telephone, networking, TV etc. There should be a separation of at least 50mm (IIRC)/ Reg is (I think) 528.1.

About to start running in network, telephone and sky cables under the floors. its very difficult to avoid paralleling cable runs along along joists, especially when you encounter a corridor which is narrow.

Any hints and tips or will twisted pair not suffer from emi if I parallel a couple of metres of mains twin and earth?

 

[Chri5]

Place a physical barrier to separate.

The barrier could be trunking, wood plank or simple sheet material (ply, mdf, even plaster board). A 1200 x 2400 cut 100mm would give you 24 x 1.2m barriers.

They wouldn't have to be fixed, just rested between the data / voice / tv and the mains cables