Installing cables in an external wall

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Dear All,

I am undertaking my own electrical work in my new extension which includes 4 new external walls.

I intend installing 2 x new external lights mounted on the outer brick of the external walls. I want the cabling to them to be concealed.

The problem is the cabling to these would have to be chislled out of the internal block in a new toilet room and also in a new shower room and then passing through the block and cavity and external brick. Whilst the chislled cable slots will then be covered with plaster and then tiles unless a future homeowner was mindful that there are external lights (which they would be) they would not know the cable is buried in the tiles behind the walls.

If I was to install the external lights in the proposed position then the cables would be dropping down the middle of these walls.

I would appreciate any thoughts on whether this is permissible. I assume it is not. I really do not want to run the cable down the external brick in SWA etc

An electrician will be inspecting and testing this work but I am asking for ideas here so I can approach the electrician.

Cheers




Paul
 
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You need to route cables within the permitted safe zones or the cable must be at least buried 50mm withith wall (this method, very rarely complies to part A of building regs though).
Or mechanically protect the cable, this can be by earth shielded cable or a metallic plate which would need to be at least 2mm gauge.

//www.diynot.com/wiki/Electrics:walls

Can this cable not be routed via the ceiling/floor void?
The cable can be routed within the 150mm of the angle of walls. When I need to do this, I place cable right in the join of the two walls,
 
The problem is the cabling to these would have to be chislled out of the internal block in a new toilet room and also in a new shower room and then passing through the block and cavity and external brick. Whilst the chislled cable slots will then be covered with plaster and then tiles unless a future homeowner was mindful that there are external lights (which they would be) they would not know the cable is buried in the tiles behind the walls. ... I would appreciate any thoughts on whether this is permissible. I assume it is not.
As you suspect, and for the reasons you give, that would not be compliant with regulations (unless buried more than 50mm deep, or 'mechanically protected - e.g. in steel conduit), because the buried cable would not be in 'safe zones'. You could perhaps create a 'safe zone' by having the cable connected to some accessory within the room which was in the (presumably vertical) line of the buried cable. In the case of the toilet, that could probably be a switch/isolator, but that probably would not be possible in the shower room (unless it were >600m from the edge of the shower) - in which case you could perhaps have a joint in the cable behind a blank plate. These are really issues which you need to discuss with your electrician.

Kind Regards, John
 
Derry,

Many thanks.

I cannot install via a roof void due to the height of the lights on the external wall.

I would like your thoughts on the pro's and con's of both proposed methods.

Is there a standard type 2mm plate available (such as a thick conduit or capping etc)

Alternatively what problems may I experience with using the earth shielded cable??


Cheers




Paul
 
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Cheers John, so I can go to the electrician with a decent proposal do you have a link to a suitable conduit.

I do not want to create the safe zone or chisell out 50mm due to the Part A regs that Derry referred to

Cheers




Pau
 
Metal conduit will normally exceed the 2mm gauge or a metal fabricator would be able to manufacture a suitable metal plate. The standard metal capping will not meet requirements.

Earth shield is a good option, tends to be bulkier and not as flexible as the T&E or flex.

If you have an electrician on board, you should really seek their advice, they may see things you don't and can comply to regs with little disruption.
 
if I was to go for the earth shielded cable how is this connected to the shield connected to earth?? Would I do this at the light switch that feeds the cable?
 
if I was to go for the earth shielded cable how is this connected to the shield connected to earth?? Would I do this at the light switch that feeds the cable?

That would depend on the cable you purchased, some are designed not to be connected.
 
The cable can be routed within the 150mm of the angle of walls.
and ceiling.
Very true, but, unfortunately ...
If I was to install the external lights in the proposed position then the cables would be dropping down the middle of these walls.
...and...
I cannot install via a roof void due to the height of the lights on the external wall.
... and I assume the latter probably means that the external lights would probably be too low to use the rooms' 'ceiling safe zones' without there being some visible external cable - which the OP does not seem to want. He seems to have decided that buried protected cable is the best way to go - but, as has been said, his electrician may have other views.

Kind Regards, John
 
OK guys thanks for your help.

Just to clarify, if I have this communicated this correctly, I am talking about installing lengths of metal conduit down 'unsafe' zones of a shower room and toilet room wall. There is a possibility the conduit may be in a shower cubicle wall.

The positions of the lights do not allow use of the safe zones and I would prefer to install equipment on the zone to 'make' a safe zone.

I think the best course of action will be to approach the electrician with the proposal that I fit the metal conduit kindly supplied in the link from Derry.

I'll feed back with what the electrician has suggested.

Many thanks




Paul
 
I dont do domestic, but I thought safe zones transferred to the reverse side of the wall ...
AFAIAA, only if the wall is no thicker than 100mm (obviously not applicable for external wall) and both sides can be seen simultaneously (again....!) ... and that's just per BS7671, so it doesn't only apply to domestic installations.

Kind Regards, John
 

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