Cabling and Wiring Methods

it is only bad practice if the cable is likely to be disturbed and is not of a type resistant to damage - so you can put cables there that have a built in earth screen that would trip something if hit my a nail. BS8436 cable is expensive, relatively, but may save the day.

A similar discussion here from a while back.

and the NICIEC view...here
"

Cables conforming to BS 8436 are listed in Regulation 522.6.204 as one of the types of cable incorporating an earthed metallic covering that may be:

● Concealed in a wall or partition at a depth of less than 50 mm from the surface, without being run in one of the prescribed zones"

Mike.

Hi,

So does that basically mean if I was to utilise BS 8436 cabling, it doesn't need to conform to part M? Therefore the safe prescribed zones? What about RCD protection? Appears as though overcurrent is sufficient?

It doesn't need to conform to part M in relation to the minimum height of accessories, as it is not a new build. But the future occupancy of the building might require a minimum height 

Old skirtings in old buildings tend to be quite high anyway so you shouldn't have problems with bent flexes under plugs.

Sockets need RCD anyway as does lighting in domestic.

Routing should be within prescribed zones. 

Thinking whether the panelling extends to the floor behind the skirtings, there could be a massive gap behind if not, as possibly no plaster there either.

Anyone working in the future screwing stuff to the boards may have to read any documentation first, which could outline cable routes, plans, elevations etc

part M and the safe zones for unshielded cables are two different things.
For part M is concerned with the ease of use of the installation to people with limited mobility, and that usually means having all light switches and enough sockets that you might expect them to want to use at sensible heights, sort of between knee and shoulder height. Chat to the building control office as usually in an existing building there is considerable flexibility - and you can always have extra sockets outside that band - even on the ceiling if you want (that is something I have done for real, for projectors and stuff) so long as they do not need to be touched during normal use.
Safe zones require cables less than 50mm from the wall surface and not constructed with an earthed shield to be vertically or horizontal  inline with a fitting or in a corner or run round the ceiling. But a cable in the skirting with an Earthed shield, or a plain cable but deep enough to avoid a 50mm nail, is fine anywhere. As  is any cable in an earthed metal conduit.

Mike

My apologies for not being detailed in my query about Part M. How does part come into effect in terms of obstacles being in the way of part M requirements? If you can't adhere to them? Building regs would have to sign it off then, as being practicable? That was my question but you have answered that query. Do BS 8436 cable a metal conduit behind skirting board installation for cabling?

I'm not sure I understood you in that last bit !
A BS8436 cable has a metal foil screen between the outer jacket and the cores within, and in a sense brings its own very thin flexible earthed conduit with it. It does not stop a nail, where traditional conduit might, but it does trip the power off as the nail goes in, so the regs allow it in those zones where an ordinary cable like T and E  could not be used.
Basically, follow the cable makers instructions in terms of breakers and ratings and so on, and you can route it where and how you like, without regard to 'zones'.

Mike.