Loft conversion celotex advice

[Electric_Yoda]

Hi guys

Firstly hello - I've been lurking on here a while soaking up all the useful info but this is my first post.

I will shortly be wiring up a loft conversion. The stud walls will be insulated with celotex (or similar) then plasterboarded.

Running a radial for the sockets. What is the usual method for installing the cables taking into account the insulation ? Is there a way to avoid derating the cable ? If they are in pvc conduit, cutting away celotex etc.

Any advice/top tips appreciated.

Cheers

 

[Apache]

Firstly hello -

Hello! :^O

I've been lurking on here a while soaking up all the useful info but this is my first post.

Oh no it isn't! Remember you asking about your exams?

I can't help with your question - sorry.

 

[Electric_Yoda]

Oh no it isn't! Remember you asking about your exams?

Doh !!

You're right of course - confused my forums :^O

 

[ProDave]

When running cables in celotex insulated walls, just run them behind the celotex, i.e put the cables in first right at the back. Then when the celotex is fitted the cable is only against the insulation in a clear air gap (there must be an air gap) so no derated needed.

Where accessories are fitted you have to drill a small hole to pass the cable through. The distance is so short no derating needed.

Ideally the required insulation is made up in 2 sheets of celotex, so just a small hole through the outer one to pass the cable, then cut a clearance hole in the second sheet to clear the back box, then use a plasterboard box.

 

[JUD]

When running cables in celotex insulated walls, just run them behind the celotex, i.e put the cables in first right at the back. Then when the celotex is fitted the cable is only against the insulation in a clear air gap (there must be an air gap) so no derated needed.

That's OK unless there are any cables in partition stud walls, in which case it would have to be Ref. Method A or 102

 

[ProDave]

I had assumed it was only the outside walls that are celotex insulated. I've never come across Celotex being used to insulate a stud partition wall, though I guess sometimes it's done.

 

[M107]

I had assumed it was only the outside walls that are celotex insulated. I've never come across Celotex being used to insulate a stud partition wall, though I guess sometimes it's done.

Just put in some lectrickery to an ensuite with stud walls with xtratherm (celotex competitor) insulation in stud.

I cut the xtratherm so cables were not in contact & put in verticle noggin to make a uninsulated channel for cables.

But I have done as already posted, clip cables to external wall & leave air gap between external wall & celotex.

Did a whole garage/boys drinking den like this, pics might still be here on the forum.....must remember to take some more pictures while working, not posted any for ages.

 

[JUD]

I had assumed it was only the outside walls that are celotex insulated. I've never come across Celotex being used to insulate a stud partition wall, though I guess sometimes it's done.

Guess it depends on LABC. Some of them want ridiculous amounts of insulation everywhere.

 

[Andy™]

for those who are putting downlights in a ceiling with kingspan (yet another name!), make sure you dont let LABC holes in the kingspan. while back i done a job with downlights, drilled a 150mm hole through kingspan, ready to drill 80mm hole once boarded. LABC inspector saw this, and demanded rockwool ontop of the kingspan!

 

[Electric_Yoda]

Thanks for replies guys.

There is a void behind so I should be able to utilise that and then just come thru the insulation where necessary as suggested.

E_Y

 

[ianmacd]

External Stud walls should have an airgap to run cables in between the celotex. This is either because the celotex is pressed to the back of the studs or because its been overbattened.

New flat roofs should be warm roofs so no insulation to worry about at ceiling as its all above rafters.

 

[Electric_Yoda]

Cheers Ian - I notice you are in Sussex. I'm just outside Brighton !

 

[ianmacd]

Worthing. Not too far away.

If you wanted some more info about celotex installation then their site contains loads of useful info about how to install it and one specifically for loft converstions:

http://www.celotex.co.uk/Applications/Conversions/Loft-conversions with a link on the right to a pdf:

http://www.celotex.co.uk/downloads.asp?i=28 (may need to be logged in to view this file)