In what circumstances does electrical cable need to be protected when
buried in plaster? I am guessing that wires leading up from under the
floor directly to the socket do not need any kind of protection (steel
conduit for example). Is that right? I mean it would take a complete
idiot to start drilling under a socket! Or maybe we have gone so far
down the health and safety route that all buired cable needs
All buried cable does need protection now, unless it's RCD'd
Or to put it the other way, RCD protection is now required for all
buried cables unless they are in conduit or have an continuous earthed
This may change with an amendment to the Regs, especially for minor
alterations to existing installations.
Had to tease a mate of mine once for nailing a picture rail back on a
wall with masonry nails - right into the new plaster that was filling a
cable chase drop to a light switch!
(by fluke it seemed he missed the cable!)
In my parents old house - putting up a shelf or cabinet or something. I
plugged an electric drill into a socket and then proceeded to drill a
hole in the wall above the socket......
No, I have no idea what possessed me either.
Oh um yes WHAT? You don't need to empty the bowl until the job's
done. Come to think of it, you don't even need a bowl. Just empty
the U bend into the sink. With the plug in place.
Then clean out the U bend in said sink, with plenty of water.
Just remember to re-connect the bend before pulling the plug!
There's nothing particularly moot about this; the regs are quite clear.
No mechanical protection  is needed for cables that are in the 'safe
zones'  AND are 30 mA RCD protected.
If you want to stray outside the safe zones you need mechanical
protection, or one of the prescribed protected types of cable. The RCD
is than optional from the point of view of cable protection, but may be
required for other reasons - circuits feeding general-purpose
socket-outlets, high earth fault loop impedance, etc.
The use of top-hat capping (metal or plastic) is good practice and
protects the cables during construction and plastering, but it does not
constitute mechanical protection in the sense of this thread.
 Prescribed 'self-protected' cable types, or earthed conduit or
trunking, or measures to prevent penetration by nails or screws
(generally interpreted as min. 3 mm thick mild steel).
 Horizontally or vertically to a visible electrical fitting or wiring
accessory (which can be on the 'other' side of the wall if this is
accessible), or within 150 mm of a corner, or within 150 mm of a ceiling.
OK, it is all making more sense now, but there is one thing I just
My situation is that I am planning to add a socket in a stud wall, my
idea is to add an extra noggin with a cut out in the noggin to fit a
metal back box. The cut out will be exactly the right depth so the
mounting box is flush with the wall surface.
As the cable needs to be in an earthed metal conduit, I could use
But how to "connect" this to the mounting box and satisfy the earthing
Although my main problem is that with this conduit in place there is
no longer any room for the plasterboard! The conduit needs to be at
least 12.5 mm from the front of the mounting box, and obviously this
isn't so. So how to do it?
Incidentally are there any guidelines about how to prevent someone
drilling from the other side of the stud wall straight through the
mounting box and into the socket itself. If a plastic drywall box had
been used then this is easily do-able with a SDS drill. It seems daft
to go to all this trouble to protect the cable when the actual fitting
is quite defenceless. This is why I have chosen a metal mounting box.
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