Safe Wiring Zones
Wiring zones are designated areas within the building fabric that are designated as safe wiring zones for the installation of concealed/buried electric cables.
With the release of the 18th edition of the Wiring Regulations, “safe zones” were renamed “prescribed zones”.
A safe wiring zone is designed to be areas where electrical cables can be installed and are less likely to be damaged and/or penetrated (i.e. drilled) in those zones.
Because the wiring zones have been predefined by BS 7671, there is an expectation that electrical cables might be installed within those zones, hence a lower risk of being penetrated.
Wiring Zones Around Walls and Ceilings
The prescribed safe wiring zone for walls is up to 150mm out from the corner or edge of the wall. For ceilings the safe wiring zone is up to 150mm down from the ceiling.
BS 7671 Wiring Zones
Prescribed zones in accordance with BS 7671.
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Safe Wiring Zones and Electrical Accessories
The safe wiring zones around electrical accessories such as socket-outlets, light switches, cooker switches etc. extend directly above and below the electrical accessory and directly to the left and right of the accessory.
This zone does not extend around corners or across on to adjacent/adjoining walls, unless a socket (or electrical accessory) is installed on that wall, which in turn would create a new wiring zone.
It is not permitted to install cables between electrical accessories (such as a cooker switch and cooker outlet for example) diagonally between the outlets as this will very likely be outside of a prescribed zone.
Cables in Walls RCD Protection
In addition to the requirement of installing cables within a safe wiring zone, buried cables (buried less than 50mm in the wall, or within a wall containing metal parts irrespective of depth) also require suitable RCD protection if no suitable earthed mechanical protection has been installed to protect the cables from mechanical damage.
SWA (Steel Wire Armoured) cables are said to offer enough mechanical protection (if installed properly) to satisfy this requirement.
It is not permitted to install electrical cables outside of a prescribed zone (safe wiring zone).
Wiring Zone Diagram
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