Lighting Wiring Above Kitchen Extension

[loopy66]

Hi. I am replacing my kitchen roof shortly. It is a cold deck flat roof (built years ago) with not ventilation and has basically rotted from the underside over the years, now leaks and is generally just a piece of rubbish.

I will be replacing it with a cold desk style again (warm roof would raise the height too much) and will have the proper ventilation, EPDM covering and such.

With the scene set, my question is about the lighting wiring. I will be using Celotex type insulation boards inside the roof, leaving the gap between that and the outer roof for the ventilation but, what should I do about the wiring? Can the lighting wiring run underneath the insulation, ie, the Celetex boards sit on top fo the wiring or do I need to do something else?

 

[EFLImpudence]

Yes, lighting is usually on a circuit with 6A MCB and cable capable of carrying 16A, so even with the most derating because of thermal insulation is still satisfactory.

 

[securespark]

IIRC, you should allow for vents in the 50mm space above the insulation.

 

[ban-all-sheds]

Are you sure that by the time your new roof has been done to meet the current requirements for thermal performance that it will be thinner than a warm deck?

 

[loopy66]

Thanks guys regards the lighting wiring, appreciate the input.

Regards the thermal stuff and regulations, the last time I spoke with the council planning guy it seemed all within and ok but, this was about 6 months ago to be honest. Are there very new requirements? I really do need to keep the roof height the same so need to avoid a warm deck unfortunately.

 

[ban-all-sheds]

Not sure how new it is, but when you replace thermal elements (such as a flat roof) it has to comply with the current requirements, not with what applied at the time it was first built.

That may make the whole roof thicker than it was, which will mean either greater height outside or lower ceilings inside.

Planning are not the people to talk to re Building Regulations - speak to Building Control. It's notifiable work, so you can't keep it a secret, and they would much rather you got it right from the outset than end up in a conflict.

 

[Notch7]

can you not do some insulation over the top and some in between?

 

[loopy66]

Sorry... I named the wrong department, it was the Building Control guys I spoke with I will call them again and run through the plans and see what they say before submitting the application.

The frustrating thing here is, I got some guys out previously to quote me a new roof and they all wanted to do a cold deck style but never mentioned ventilation and when I asked about ventilation they asked me sarcastically how it would work, like I was talking rubbish. I just knew that they wouldn't be doing the job right nor putting it through building control so, threw the quotes away and resigned to doing the job myself. Anyway, probably best I call building control again and make sure of any newer regulations which might not give me the 50mm ventilation space above the insulation... like you say, I may even have to think about lowering the ceiling on the inside to make it work.

Notch7, I am not sure, all designs I have seen so far have been one or the other.

 

[SUNRAY]

Do you need to inform BC to replace a rotten roof?

 

[Notch7]

Sorry... I named the wrong department, it was the Building Control guys I spoke with I will call them again and run through the plans and see what they say before submitting the application.

The frustrating thing here is, I got some guys out previously to quote me a new roof and they all wanted to do a cold deck style but never mentioned ventilation and when I asked about ventilation they asked me sarcastically how it would work, like I was talking rubbish. I just knew that they wouldn't be doing the job right nor putting it through building control so, threw the quotes away and resigned to doing the job myself. Anyway, probably best I call building control again and make sure of any newer regulations which might not give me the 50mm ventilation space above the insulation... like you say, I may even have to think about lowering the ceiling on the inside to make it work.

Notch7, I am not sure, all designs I have seen so far have been one or the other.

Some people would call it a hybrid roof. Celetex and others havent done testing for it so dont offer as an option.

However a small amount over 25 to 50mm would reduce cold to joists, so chance of condensation is very very low, personally I think a much better option than a cold roof with inadequate insulation and downlighters.

 

[ban-all-sheds]

Do you need to inform BC to replace a rotten roof?

It's notifiable work - plans submission, approval, then start work, then inspections and completion certificate.

 

[JohnW2]

Do you need to inform BC to replace a rotten roof?

We seem to be being told that one does. If that's the case, it's different from the approach to electrical work - as I understand it, even pre-2013 (and still in Wales), one could replace almost any 'broken' bits of an electrical installation (with 'similar', the dreaded "like for like" often being unworkable!) without it being notifiable.

Also, if so, I wonder where it starts. Over the years, I've had a good few tiles replaced, and also a few 'failed' roof timbers, bits of sarking etc., and it's never even occurred to me that such work might be notifiable. Where does 'maintenance' stop and (maybe only partial) 're-roofing' start?

Kind Regards, John

 

[ban-all-sheds]

Do you think that people should be allowed to replace any roof timbers without assurance that the replacement work will be structurally sound?

 

[JohnW2]

Do we think that people should be allowed to replace cables, electrical accessories etc. "without assurance that the replacement work will be electrically sound"?

 

[ban-all-sheds]

No.