Routing cables when insulated plasterboard direct fix to walls

For me it was better insulation for the money and easier to work with - the insulation backed plasterboard I received was flimsy and also had no (or just one) vapour barrier. I realised I could get double the insulation and a separate plasterboard for about the same price. Much easier to work with separates.

As with SFK, room size a thing too - my ceilings are 250cm, so offcuts used for the top of the wall - again, easier. But also better vapour barrier, as you tape over all the joins before putting the plasterboard up - with ready bonded boards you cannot do this.

And ... I insulated my floors too, so anything that was left over from the walls can be used in the floors. I have not thrown any of that expensive insulation away yet, and now insulated 4 rooms (just 1 room, 1 wc and hallway to go!). So less waste than the bonded stuff.
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I did floor first so they got the big sheets, last wall got most of the bigger offcuts, but I even used the small bits, taping them together and putting them in the loft between the joists and under the existing insulation. Room is now almost entirely in an aluminum / PIR box.

Only annoyance is that I think I have used it all, finish the job and then when tidying up I always find a largish bit of PIR hiding behind something. The latest bit of PIR i found is now sitting in garage waiting for my next visist to the loft or DIY job. :>
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yeah, I've not finished yet, but if anything left over it will go in loft - go a cold spot in the old shower room that keeps getting mouldy, so need to insulate better up there.
Seem to have stopped getting notifications for this thread, so missed these replies.

The photo Jonbey used is exactly the same as how I did it.

I had been planning to put the tape on the other side of the cable, because I thought it would be to have the foil reflecting any heat generated by the cable away from the insulation rather than towards it. i.e. fit the insulation, tape the channel, run the cable, then fit the plasterboard. I thought this might be better but maybe I am splitting hairs.
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Just for information, for anyone coming to this later, I've also been continuing to look into the skirting board conduit thing. I contacted a couple of the manufacturers who initially said yes its fine to run mains cable in the channels cut in their skirting, however I pressed them on whether they were confident that this met the current electrical regs they went a bit quiet. I also found this discussion on another forum where the person arguing for using skirting to run cables was making the point that if the skirting has been manufactured with a cable rebate then it is technically a surface mounted conduit. I suppose my concern is that a normal surface mounted conduit is obviously that, while a skirting board is not. As I can do what I need to by running channels on the surface of the insulation and staying in the safe zones I think that might be the better option.

My next problem is that I have just found that the existing/previous configuration is a spur from a spur. I know this is not allowed, but can anyone comment on whether a spur from a spur is allowed under any circumstances? For example if I added a fused junction box between the ring and the double spur?
I cut channel in PIR, then lined channel with metal tape to have a continuous vapour layer.

For me Cables then loose in channel, and plaster board on top.

Reason being that then cable a bit loose and can then have a bit of slack to pull cable in an out a bit, and cable next to board so some cooling effect.

I cut channel in PIR, then lined channel with metal tape to have a continuous vapour layer.

For me Cables then loose in channel, and plaster board on top.
Thanks SFK, sounds like we are describing the same thing, but in the photo it looked like the tape was over the top of the cable.
Don't understand why trunking on top of the insulated plasterboard won't do, although cables are not so well protected. Incidentally, a company makes breathable, solid-wall insulation that creates minimal condensation behind it.

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