I'm planning to do a partial house re-wire. Existing cabling is sound
and legal (16th edition) but I need to add some additional sockets and
I also want to split the ring main from existing single RM circuit to
create two rings (Kitchen and rest of house).
Question: Do I have to cover the cables with either plastic or metal
capping or is this optional ?
The 'On-Site Guide" will tell you you this (and lots of other useful
Cables don't have to be capped in any way (i.e. can just be buried in
the plaster) if they are in 'permitted areas', these are (basically):-
150mm band of wall adjacent to a vertical corner.
150mm band of wall below ceiling.
Vertically from an exposed accessory (e.g. switch or socket).
Horizontally from an exposed accessory.
Ouside of these areas buried cables must either be capped with a metal
protection or be at least 50mm deep.
This is all from memory so check it before doing all the work, as I
said I suggest you get a copy of the "On Site Guide".
Does the capping really have to be earthed? Is it a recent
requirement? The reason I ask is that when we had our kitchen
installed a few years ago the electrician applied some capping to some
cables that would be buried diagonally in plaster but I saw no sign of
the capping being earthed. He seemed competent as far as I could
I've just had my kitchen refitted and was chatting today (ok -
yesterday!) to the electrician doing his 'second fix'. The old cables
which he recovered last week were capped with plastic capping - the
new ones he simply laid vertically beneath the plaster-to-be (even for
some very adjacent socket-outlets).
He used to work for Moben but left on account of their cowboy sort of
image and now chiefly sub-contracts for local installation firms.
He was saying however that Moben used to insist on steel conduit for
all their installs. As he said, even metal capping hardly resists
most modern things driven into walls such as hardened pins.
Realistically, I think that if anybody brays a hole of any sort into a
wall without checking for wiring behind, they deserve all they might
If you are outside of the permitted zones and not >= 50mm deep then yes.
(iii) below seems to allow unearthed protection but only if it is man
enough for the job.
So since capping alone (even metal) provides relatively little
protection it would need earthing.
The relevant bit of BS7671 is:
"522-06-06 A cable concealed in a wall or partition at a depth of less
than 50 mm from the surfaces of the wall or partition shall:
(i) incorporate an earthed metallic covering which complies with the
requirements of these Regulations for a protective conductor of the
circuit concerned, the cable complying with BS 5467, BS 6346, BS 6724,
BS 7846, BS EN 60702-1 or BS 8436, or
(ii) be of insulated concentric construction complying with BS 4553-1,
BS 4553-2 or BS 4553-3, or
(iii) be enclosed in earthed conduit, trunking or ducting satisfying the
requirements of these Regulations for a protective conductor, or be
mechanically protected sufficient to prevent penetration of the cable by
nails, screws and the like, or
(iv) be installed in a zone within 150 mm from the top of the wall or
partition or within 150 mm of an angle formed by two adjoining walls or
partitions. Where the cable is connected to a point, accessory or
switchgear on any surface of the wall or partition, the cable may be
installed in a zone either horizontally or vertically, to the point,
accessory or switchgear. Where the location of the accessory, point or
switchgear can be determined from the reverse side, a zone formed on one
side of a wall of 100 mm thickness or less or partition of 100 mm
thickness or less extends to the reverse side."
I was just by chance talking to an Electrician who told me that he
covers all cables with plastic cladding when its' a new build
property. He says he does this because Plasterers have often damaged
I just called my local authority re building regs and approvals...
They told me, I have to fill out a form (which he as put in the post)
They will inspect after 1st fixing is complete then again after 2nd
Total cost =A3170 which seems reasonable to me ....
I didn't mention it was a partial rewire but I assume I will be able
to state this on the form so there's no problem when the guy arrives
to inspect 1st fix and finds light fittings and some sockets already
I would phone again and ask what the standard building notice fee is. If
it is less than that you could ask him to explain why they charge more
when it is in direct contradiction to section 1.26 of part P of the
Tried to raise my next question under a new topic but seem to have
failed so I'll raise it here ........
I need to also sort out the earth bonding in the bathroom and kitchen,
I assume that this involves making sure that the Hot and Cold water
supply to sinks, baths and showers are bonded together, but should
there be an earth cable from the bonding in each of these areas back
to consumer unit or can this be connected into the back of the nearest
power socket and what size does the earth cable need to be ?
So, for a cable in a wall:
(i) The cable has to be armoured.
(iii) In an earthed conduit OR physically protected from nails etc.
(iv) In a special zone.
I don't see how any of this is relevant to steel capping, the only
purpose of which is to protect cables from the plasterer.
well metal clad - MICC for example.
Correct... and that is the point at which we came in, highlighting that
Tim's original comment of "Outside of these areas buried cables must
either be capped with a metal protection or be at least 50mm deep." was
only partly on the money since it needs to be earthed protection (or
seriously strong) to serve that purpose.