Electrical cables and insulation?

[Brazen]

Hello All,

I have reinforced my ceiling and roof members by adding 4 7x2 joists at 90° to the existing ceiling bearers fixed to the endwall using joisthangers and through bolts to the gable walls, then adding noggins between them at the same centers as the existing celing bearers, these will be boarded over using 12mm flooring chipboard (This was reccomended by a structural Engineer).

The question i have is reguarding the electrical cables in my loft i was unable to lift them over the new timbers because of insufficent slack and I'm loath to take them out of the ceiling rose and extend them (possible Part P problem). I intend to insulate in the near future with 10" of a rockwoll equivilent and I'm aware that cables should not be trapped under insulation because of possible heat build up, can i use something to box the cable in so they do not come into contact with the insulation, I.E large white clip on conduit or is there another product i could use? Or do i have to split the circuits and extend them using joint boxes so that they lay ontop of the insulation ?

Any advice would be greatfully recived.

Cheers

Richie

 

[Gteuk]

You are in a grey area here as it depends on the circuit and the lighting involved. Most lighting circuits use 1.5mm cable that is capable of taking 19 amps not calculating voltage drop.

I essence they should not heat up unless there is a fault in the circuit or you are overloading the circuit.

to be safe you can use rock wool slabs and put beeding in place to allow air movement, what I mean by this is 25mm from the bottom of the joist add a lip so the insulation sits on top of it.

however if the ampage and distribution of the electricity is not too great the insulation will not make a great deal of difference, this is usually as the MCB is rated at 5 amps but wiring at 19 amps