What Are Electrical Safe Zones?
Posted: 22/02/2023
4 minute read
What are electrical safe zones?
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What Are Electrical Safe Zones?

Electrical safe zones are areas where cables can be installed so that they are less likely to be damaged accidentally by anyone drilling or hammering through them. 

More recently, the name for electrical safe zones has been altered to ‘prescribed zones’, although you may also see them referred to as ‘permitted zones’. They all mean the same thing: they are simply areas outlined in BS 7671:2018 for the positioning of concealed cables installed at a depth of less than 50mm. 

As well as answering the question of what electrical safe zones are, this month at Surrey Tech Services Ltd, we wanted to provide a little bit of additional context and information. This will include why we actually need these zones and some more detail on what the specific zones are.

What are electrical safe zones?


Why do we need electrical safe zones?

All buildings requiring electricity – so pretty much all homes and businesses – will have cables running through and along walls. In addition, the installation of sockets and power points will require electric cables, and no one wants all of this wiring exposed due to both how it looks and how vulnerable to damage it could be. 

As you can imagine, running cables just behind walls in a haphazard fashion could be equally dangerous. That’s because eventually, someone may want to drill, hammer or cut into the wall, resulting in both a loss of power and the potential for serious injury. 

Until regulations were introduced, cables were installed in a less regimented and less uniform manner, which is why you need to work very carefully in some older buildings. 

The 50mm depth outlined in the regulations is important to note, as this comes from most people wanting to avoid cutting too deep into their walls to install cables. This is because many walls won’t run very deep, risking damage if too much of the wall is chased.


Electric safe zones and building regulations

Let’s take a look at where the electrical safe zones are for walls according to the BSI (British Standards Institution).

  1. Along the top of the wall. This zone runs along the area where the wall meets the ceiling and is a 150mm-thick strip.
  2. Where walls meet. Corners where walls meet are considered safe zones, again at 150mm depth on either side of where they meet, whether they’re internal or external. This zone runs up the length of the wall, from floor to ceiling.
  3. Where electrical accessories are installed. Where an electrical accessory is located, such as a socket or light fitting, the cables should be run in a straight line vertically, both above and below it, or horizontally on either side in a straight line. This applies to the wall on which the installation sits only, it does not carry on around any corners.
  4. Where walls are less than 100mm in depth. If a wall is no thicker than 100mm, the safe zone on one side is also replicated on the other side of the wall.

Other things to note about electrical safe zones:

  • They don’t extend past a doorway. For example, a light switch will have a safe zone horizontally on either side until it reaches a doorway, but this zone is not carried on to the other side of the doorway.
  • It’s common practice to situate cables running horizontally at the same level on different walls so that the zones can continue in connection.
  • If a cable cannot be run in the specified zones for any reason, they will have to comply with a variety of other protective measures.


Here at Surrey Tech Services Ltd, we take electrical safety and adherence to the relevant regulations very seriously. That’s why our clients in London and the Home Counties – including Maidenhead, Guildford and Slough – trust us as qualified commercial electricians. We can provide a variety of electrical services, including electrical installations and electrical office fit outs.

Call today to discuss your electrical requirements or to book an appointment for work to be carried out in your building.

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