Cabling - Rubble / Lime Walls - Safe Zones!?

[GPHouse]

Hi All

Hi

I'm not a novice from a wiring perspective but from a regs perspective I haven't got a clue. Hoping some people have experience they can share!

I will be engaging an electrician for a load of works but need to do some prep work as part of the renovation - particularly around chasing / walls and cable route planning.

I have a 230yr old cottage with dual rubble walls and clay / lime plaster (60mm) which is a little fragile but still functional. There is some existing wiring circa 10yrs old running ring mains to a consumer unit.

I am currently looking at adding some sockets and in part of the building I am doing some work... BUT....

[*]Given non standard joist sizes and the fragility of the plaster I cant run new cabling in the traditional safe zones without compromising the structure or the original features / plaster.

[*]Are Safe zones a recommendation or a requirement when working with LABC?

[*]There is a natural void behind the skirting - If a method of trunking cables behind the skirting, and affixing the skirting in a regularized (and obvious way) would this be acceptable as risk mitigation? If so could I get away with 1" rectangular trunking (plastic as lime and many metals dont play well) or would I need to go for stainless steel conduit?


Any help gratefully received!

 

[noj]

According to the regs so far as I can see...

If you're adding a spur from an existing ring it's not notifiable but if it were (or you want to do things the 'correct' way)

A cable concealed in wall or partition must:
1) be at last 50mm from the surface, or
2) have earthed armouring or an earthed steel conduit or trunking, or
3) be enclosed in earthed steel conduit or trunking, or
4) be provided with mechanical protection sufficient to prevent penetration of cable by nails , screws and the like, or finally
5) be installed either horizontally within 150 mm of the top of the wall or partition or vertically within 150mm of the angle formed by two walls, or run horizontally or vertically to an accessory or consumer unit.

The safe zone runs at the top, but not bottom, of a wall - but using earthed armoured cable in the void behind the skirting could comply with regs and completely avoid the need for any trunking?

 

[GPHouse]

Thanks.

And I think the question you have is the crux of it, is using earthed armoured cable in the void behind the skirting could compliant with regs??

G

 

[noj]

According to the way I read them it is...

It's cable not installed in a 'safe zone' and so it should be either buried at least 50mm (not practical), be in nail proof earthed steel conduit (not practical) or be armoured and earthed.

Caveat: this is my interpretation!

 

[GPHouse]

Star. My interpretation too. Will post what the electrician says too... and then LABC. I have a feeling the latter will be 'helpful'.

 

[Tony.]

http://electrical.theiet.org/wiring-matters/54/cables-in-walls/index.cfm

See the above link from the IET form more info

 

[Tony.]

http://electrical.theiet.org/wiring-matters/27/cables-in-wall.cfm?type=pdf

Another link, cables not 50mm below need not be steel wired armoured cables,(swa) but appropriate cable with a metallic conductor over the conductors, smaller than swa, easier to terminate.

 

[GPHouse]

so sheatheed with sheathing earthed... or full mechnical protection (read impenitible conduit) are fine. A couple of choices - this will make life a little easier if not a little more expensive - although still cheaper than pyro/MICC

 

[88v8]

Our cabling runs pretty much anywhere. A lot of it is surface.
Where it's in the rubble walls it's buried in the meandering joints, often less than an inch deep, no conduit..

Our electrician takes the view that as we have a modern 'fuse box', it doesn't matter.
Would of course be a nuisance if I put a nail through it, but not lethal.

Ivor

 

[Flyfisher]

We also have a fair bit of surface wiring, much of it within conduit. Actually, I tend to prefer surface conduit to surface wiring - once painted to match the background it's barely noticeable and certainly no more than some of the heating pipe work. It's that delicate trade off between disturbing original walls to bury cables versus personal preference.

I presume that 'safe zones' only apply to hidden cabling as it seems unlikely that anyone would put a nail or drill bit through a visible cable. Our electrician took the same view as 88v8's when installing new consumer units, didn't flag our wiring layout as a problem and was happy to sign everything off.

 

[a twig]

My sparky signed off on bog standard T+E just running behind the skirting - he was however completely incompetent, and could barely tell one end of a screw driver from another - so I guess that's not much help...

 

[GPHouse]

Thanks a Twig - he sounds just like the kind of Sparky I need to sign off my wiring!

 

[a twig]

Hypothetically - and obviously I would never suggest or condone such actions, but I've heard of others talking about the possibility - you could of course buy a large amount of this to do the wiring work behind the skirting:

http://www.ebay.co.uk/itm/like/171165415234

And some old looking sockets

http://www.ebay.co.uk/itm/Vintage-R...l-Socket-Plug-Switch-13A-250V-3-/282307617328

and claim it was all original from when you bought the place, significantly predating modern safe zone regs, and nothing to do with you what so ever, so how about we just test it and when it passes just leave it where it is nice Mr Sparky... :twisted:

 

[Tony.]

Do you have rcd's fitted to the existing consumer unit?
Earth conductors to gas/oil main pipes if applicable
Same with water?
What exactly is the scope of works?

 

[Zebra]

The concept of wiring behind skirting will result in an appalled facial expression from most electricians. However, noj's list of requirements is correct. A cable must be EITHER in the safe zones, OR be deeper than 50mm OR be protected by mechanical protection sufficient to prevent penetration by nails and screws OR be in earthed metal conduit or trunking OR have an earthed metal sheath.

So you could, technically (your electrician might not like it and you might have to show them the relevant page from the regulations...) hide it behind the skirting if you used armoured cable or one which has a metallic sheath. I don't know much about the specs for cables whose metallic sheaths can be used in this way. Have a look at this thread on an electrician's forum for cables which might be suitable http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=24712.

I'm afraid twig's idea of using old materials and claiming it was all there since forever won't get you a clean certificate, because when an installation is tested, it's tested against the current version of the regulations, so any non-conformances will be pulled up, whether they were installed last week or twenty years ago.

 

[a twig]

I'm afraid twig's idea of using old materials and claiming it was all there since forever won't get you a clean certificate, because when an installation is tested, it's tested against the current version of the regulations, so any non-conformances will be pulled up, whether they were installed last week or twenty years ago.

If it's "already there" when the sparky turns up though, and there is no further work being done to it, it wouldn't need to be tested? I don't think many sparkies that will go round pulling off skirting boards just in case...

Anyhoo, it is thin ice, and the regs are there for a reason, it's no coincidence that house fires caused by electric are at an all time low...