Insulating and boarding a loft

[Galland]

Hi there, this is my first post and I am looking for some advice. I have started to replace the 20+ year old insulation in my loft with 100mm glass insulation between the joists. My intention is then to add 100mm insulation board with tongue and groove chipboard to make a storage surface. I have this pretty much planned out, but my question relates to electrical safety. Currently the cables for power and lighting and P clipped to the sides of the joists. Clearly I cannot cover these with 100mm of insulation.
Being a tight Yorkshire man I want to avoid having to get an electrician in to rewire unless absulotely necessary. Now, I am quite capable of doing this work myself but the law doesn't allow this any longer, but I think that there may be a cheaper and quicker solution. If I were to run trunking between the joists and the insulation (with the correct airspace ratio of course), and then insulate over the top, does this meet building regs, and more importantly, is it safe? This would mean that no rewiring would be necessary and save me money as my budget is already stretched. Thanks in advance.

 

[foxhole]

No problem covering lighting cable, you have ring cable there as well?

 

[Galland]

Yes, there is a ring main and there is 6mm cooker cable too. The house is "split level", that is upside down in plain English. The living room and Kitchen are upstairs and the bedrooms downstairs. The cables for every part of the house are laid in the loft, albeit only a metre or two for the downstairs power and lighting.
Regards,
Galland

 

[chapeau]

Currently the cables for power and lighting and P clipped to the sides of the joists. Clearly I cannot cover these with 100mm of insulation.

Why not? The cable will then dissipate heat into the joist and so (legally) can carry more current than if surrounded by insulation alone.

There is a simple guide which has pretty much all you need to know when doing domestic electrics, the On Site Guide http://www.amazon.co.uk/IEE-site-Guide-7671-Regulations/dp/0863418546 so spend £20 and look it up yourself. As it happens my copy is buried deep under a pile of furniture, or I'd look it up for you.

And even when you run the numbers, if you cannot clip direct to the joist (and I reckon off the top of my head you probably can) then it doesn't need a rewire. Just reroute the cables, which means extending with an additional length of cable which is crimped into the main run at each end.

You need one of these http://www.screwfix.com/prods/70036 and some of these at the correct size. http://www.screwfix.com/prods/70167 and wrap it all up with this to be sure http://www.screwfix.com/prods/61749

And it shouldn't be expensive even if you get a sparky in. Or get somebody to fit the insulation and it won't even be considered

Get the On Site Guide and work it out, it's not as hard as you might think.