Rigid insulation and wiring.

[TheBaron]

I'm after some advice. I've built an outbuilding that has insulated cavity walls, and I now want to insulate the (pitched) ceiling between the rafters with celotex - then plaster board over that. On top of the rafters I have a breathable membrane, then battens and tiles. Under the membrane I believe I need to leave an air gap. However, there's going to be wiring running around the building, lighting and sockets etc. (I'm going to use an electrician) My question is this: Do I employ the electrician first - so that the wiring runs in the air gap, or do I fit the celotex first, leaving 50mm or so, enabling the electrician to then run the wiring under the celotex - and then plasterboard over that?

 

[PrenticeBoyofDerry]

Get the electrician in first, inform them of your intention. As the cable may need thermal insulation calculation if it is routed through the insulation at any point.

 

[Chukka63]

sparky first and like you said ,get him to run wires in top 50mm so you dont have to cut the insulation more than you need too,as its a pain in the arse and i always cough my guts up cutting that crap

 

[TheBaron]

Thanks for your advice. I'll ring the electrician today. I was hoping it would be underneath - to delay the inevitable 'hand in the pocket!'