foam backed plasterboard and wiring

[gyver500]

Hi Guys,

Hopefully someone can clear this question up for me, I recently moved into a old house and I ve ripped out the old kitchen.The kitchen is to be fitted on an external wall.There are two sockets currently on the base of the kitchen wall.I am going to raise them up by about 4foot, also I am going to add another socket for the extractor fan of the cooker approx 6-7ft up the wall .Its fairly straight forward so far.I was thinking of putting foam backed plasterboard on the external wall(27mm kingspan) for insulation against the external wall.My question is, is it safe to run the cables for the sockets behind the foam plasterboard?I was thinking I would use channel conduit to fix the cables to the external wall then cut out the channels out of the foam plasterboard and then fix the foam plasterboard.Again is this safe .is there any hassle doing it this way?
cable for sockets used is 2.5mm cable.Just to add the cooker cable 6mm is also there.Any help much appreciated

 

[Chri5]

There would be cabling derating to consider if the cable was sandwiched between wall and kingspan.

Since the wall will be permanent I'd suggest conduit direct to boxes to allow for future replacement without fabric damage and to avoid derating for thermal insulation.

There would be a ref method derating for conduit, but the run are so short it's not going to affect the performance of the design you've suggested.

 

[gyver500]

cheers chris,

Just to get a better understanding

so basically cable derating would be my main concern if the cable was sandwiched between wall and kingspan.If I was to the cable/conduit channels in the foam, would I not be avoiding cable derating?

on your suggestion to run conduit direct to boxes to allow for future replacement without fabric damage and to avoid derating for thermal insulation, obviously you mean run the conduit after the thermal board has been fixed, I was hoping to make the sockets flush as possible on the plasterboard and to hide the conduit above the kitchen countertop.Can you comment on this?

Cheers man, I appreciate your input

 

[Chri5]

No I was suggesting that you fix th conduit to the brick / block wall and then chop out the kingspan to allow the board to sit correctly over the conduit.

Or you could chase the existing brick / block.

or you could do half and half.

Since the conduit will fit to the back box and the back box must be either flush or in from the board face, it depends on the back box depth and the line of the conduit as to which will be best / quickest / easiest.

 

[gyver500]

Excellent.Cheers for the advice.Ill get cracking on it.
Thanks again

 

[dt100]

Just a different method for consideration.... I recently did similar, but in order to get the room thermal efficiencies up to latest (UK) regulations then as I had a solid 9 inch wall, ended up lining with 50mm celotex/kingspan held up with 2 by 1 batons plugged and screwed into the wall through the insulation. Then covered with plasterboard.

The advantage is that the 2 by 1 leaves a nice channel to run cabling. I also found that separate plasterboard / insulation was cheaper and easier to source than the same as a bonded single item.... though this may not be the case locally to you.