wires through celotex - lighting

[unclebob1]

Good Morning,

I am covering the floor in my loft with 100mm of celotex. Upstairs wiring needs tidying up (there are a couple of twisted connections, a few choc blocs etc... plus i've been having issues with dimming lights.

So i will be looking to re-run all the wiring between the two ends coming from the consumer unit (providing their connections are sound!)

So my plan to go though the celotex is:

Drill 15mm wide hole from room through the cealing and celotex.
push through 15mm plastic pipe through the hole, and then feed wires as needed through the pipe.

Can i then fill the pipe opening with foam or is it best to leave it open? The loft space will then be boarded over (using 2"x1" to lift the boards from the top of the celotex). Wires will run in the void between the celotex (ie will directly be ontop of it) and the boards, and notches in the 2"x1" to go between joists rather then making holes between the joists.

So does the plan hang together? and can i foam the holes or is there another way of blocking the holes?

 

[John D v2.0]

Celotex won't damage the wires, it's only polystyrene you've got to watch out for. Just clip the cables to the sides of a joist and insulate round. And unless you have loads of lights make sure you have a 6a mcb for the lighting circuit.

 

[unclebob1]

The Celotex is already down, and most likely the wire will need to pass through. Light fittings and the MCB its on, will remain as they are, just tidying up the wiring at this stage!