Oh dear, electrical cables buried UNDER loft insulation...

gutovicky

Hello there MSE Forum members,

I understand that it is advised that electric cables travelling through the loft space should lie ON TOP OF the loft insulation.

At present, my loft insulation [mostly Rockwall-type, with a top-dressing of pulped paper(?)] is too shallow, at about 4" deep.
I'd like to roll out another layer of Rockwall-type insulation matting to double the depth of of my loft insulation - as is generally advised.

However, almost all of the electrical cabling in my loft lies UNDERNEATH the present insulation.

I worry that if I increase the depth of insulation from 4" to 8" I may be creating a dangerous situation.

What are you thoughts?

Thank you for your time, Vicky

danrv

It may depend on what the cable is for. I know that my 6mm shower cable needs to be on top of the loft insulation as it’s high current. 

FreeBear

Shower cable would be about the only one to give me concern too. Lighting cable, especially if you have LED bulbs everywhere will be hugely oversized, so will not suffer from overheating.

If you currently have just 100mm (4") of insulation, bung 200mm on top. There isn't a huge difference in cost, but it will future proof you for the day recommended levels are increased. 

Ben1989

The only worry is if you have the old polystyrene insulation where this can 'burn' through your wire insulation.

Mutton_Geoff

It's no problem at all. Cables are buried in all sorts of materials all the time and the regulations allow for it by applying a current derating for the type of covering.

Personally I wouldn't worry about it for a shower cable since although the current is high, showers are generally used only for a short period, unlike, say an oven. The cable may warm up but I doubt it will pose a risk. More vunerable are any connections made in the cable, hopefully there are none, but bodges in the past may reveal a junction box. These I would replace with crimps if the whole cable can't easily be replaced.

https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

GDB2222

The op may not be able to tell the difference between the cables underneath the insulation.

In general, if they are fine under 4” of insulation, doubling that should  make practically no difference.

casper_gutman

Even if covering up the cables won't cause a safety hazard due to overheating, it could at least make it inconvenient to work on the wiring e.g. if you wanted to add or move a light fitting. Much more so if you were tempted to lay the new insulation at right angles to the existing, as you couldn't just roll one strip back locally to get at a particular area. 

gutovicky

Thank you very much everybody..  You have allayed my fears...

I won't worry too much about burying these electrical wires under deeper rockwool or similar.

If I ever fit a 'power shower', I'll make sure the wiring goes above the loft insulation - just to be on the safe side...   
What about an electric cooker cable - isn't that high current?? - would you advise that to go above all insulation too?

You have also convinced me I should do a survey of the electrical wiring traveling across the loft before beefing up the insulation - mapping out which wires go where - for future reference.

Cheers, Vicky

Ebe_Scrooge

gutovicky said:

 
What about an electric cooker cable - isn't that high current?? - would you advise that to go above all insulation too?

I'd be a little surprised if a cooker cable ran through the loft - unless you're in a bungalow?  In a "standard" 2-storey house, most of the cabling for downstairs sockets & lights tends to run through the ground-floor ceiling/1st-floor floor, whichever way you want to look at it.  The cables you see in the loft pretty much tend to be for the 1st-floor lights, sockets, showers etc.

If you do have a cooker cable in the loft, might be an idea to keep it above the insulation.  Even that's probably belt 'n' braces, but I guess it'll do no harm.

gutovicky said:

You have also convinced me I should do a survey of the electrical wiring traveling across the loft before beefing up the insulation - mapping out which wires go where - for future reference.

That's not a bad idea.  Not something I've ever thought about, to be honest, but I guess it could be useful if you ever want to do work in the future.

gutovicky

That's right Ebe_Scrooge, I live in a bungalow.
Thanks for that.

grumbler

Most if not all cable are

gutovicky said:

If I ever fit a 'power shower', I'll make sure the wiring goes above the loft insulation - just to be on the safe side...

'Power shower' is just assisted by a pump - nothing really 'powerful'.

It's an electric shower, heating water, that is about 10kW and needs a thick cable, preferably not buried in insulation.