Attic cables

[woko27]

Hello,

Do cables in attics have to run through joist 50mm down from top I.A.W the regs or can they be laid on top and clipped as there won't be any boarding going down.

TIA

 

[BigJon]

You can clip them on top but preferably on the side, as its an attic its liable to have all sorts of stuff stored in it which will end up sitting on the cables and possibly damaging them.

 

[Steve]

Though if your loft is made of preformed roof trusses, you shouldn't drill through the wood. They are made to exacting specifications and calculated to use the minimum amount of timber.

 

[woko27]

Not sure about the trusses, the house is 31 years old. I would like to run them on top. could i put something on top of them to mechanically protect them? some metal capping or something?

 

[RF Lighting]

If you run the cables on top of the joiststhen you should keep them to the edges of the loft, where they are least likely to get damaged by people walking on the joists, and stuff being stored in the loft.

Also unless your joists are over 4" thick (which is very unusual for lofts) then you will not be able to achive the required 50mm from the top and bottom of the joists.

Also as crafty said drilling joists / trusses in a loft is not a good idea.

 

[BigJon]

Is there a lot of cables? Would be installing a trunking an option? 2x2 plastic or something like that

 

[The Jeep]

The trouble with clipping to the side of the joists is there's often loft insulation there and little room for the cables, even at the top (thermal insulation touching the cable alters its current rating).

I recently did a job where I nailed down some small planks running across the loft and then clipped the cables (3 circuits) to the top. These were placed towards the back of the loft where they were out of the way. This loft wasn't floored and had no ladder, so wasn't used for storage, otherwise placing the cables in PVC trunking, fixed to the planks, would've been a good idea.

How many circuits are you running? If running grouped cables (particularly in trunking), pesky grouping factors (and the 45% fill factor for trunking) will have to be considered...comments anyone?