Before you drill: cables, pipes and studs

Where cables are allowed to run

Electrical Safety First, the charity, puts it like this:

Remember it is required that cables buried in walls are installed either horizontally or vertically from electrical accessories like socket-outlets or switches.

The wiring regulations, BS 7671, set out the zones in Regulation 522.6.202. NICEIC explained it in a technical article in Professional Electrician (14 August, 2023). The regulation covers cables installed in a wall or partition of traditional construction (for example brick, block or timber) at a depth of less than 50 mm from the surface of the wall or partition. For those cables, the zones are any of these:

• within 150 mm of the top of the wall or partition
• within 150 mm of an angle formed by two adjoining walls or partitions
• running straight to a socket, switch or other fitting: a cable must be routed to the point, accessory or item of switchgear, only in a zone running horizontally or vertically.

NICEIC adds: Where the position of an accessory, point or item of switchgear can be determined from the reverse side of a wall or partition less than 100 mm thick, then the zone also extends to the reverse side.

The zones above are for walls of traditional construction. NICEIC says BS 7671 treats walls or partitions containing significant metal parts differently to those with a traditional construction using timber studding.

So, in words: the zones are a band 150 mm deep along the top of a wall, a band 150 mm wide beside each corner that runs the full height of the wall, and strips running straight up, down or across to any socket, switch or other fitting on the wall.

A cable can also run outside the zones. NICEIC says that where a cable is installed outside a prescribed zone, the requirements of regulation 522.6.202 may also be met by complying with one or more of the methods given in regulation 522.6.204. So the zones show where cables are most likely, not the only places they can be: use a detector and take care everywhere on the wall.

Source: NICEIC, in Professional Electrician, Why contractors need to apply due diligence when installing cables embedded in thin walls or partitions. Checked 13 Oct 2026.

What the zones do not tell you

• The zones say where cables are allowed to run, not where the cables in your wall are.
• They are about cables. The sources on this page do not say where water or gas pipes run. B&Q's detector advice, below, covers both.

Check with a detector

B&Q's advice is Before fitting a wall plug, always use a detector to check there are no cables or pipes behind the area where you want to drill. Electrical Safety First adds A quality cable detector can help track buried cables before you start work. It lists Drilling, nailing or screwing close to cables in the wall. among the things to avoid.

A detector has limits. Bosch, which makes them, says A cable must have a current in order to be picked up by the device. Its steps for getting a reading:

1. To ensure the device can find the power supply, switch on electrical items such as a light or vacuum cleaner.
2. Hold the device in one hand. Place the other hand flat against the wall, around 20-30 cm away from the detection device.
3. To avoid confusing the detection device, don't wear any jewellery on your fingers or hands.

Bosch also warns: If there is insufficient grounding, for example, due to insulating footwear, or if you are standing on a conductor, it won’t be possible to detect live cables. So a clear reading does not prove the wall is clear: switch off and take care everywhere.

Sources: B&Q, How to fit wall plugs. Checked 12 Oct 2026; Electrical Safety First, DIY-ers safety advice. Checked 12 Oct 2026; Bosch DIY, Better safe than sorry: take the time to check the walls before you start drilling. Checked 12 Oct 2026.

Switch off, then drill

For any DIY near electrical wiring or power supplies, switch off the power at your fuseboard and, where possible, only use battery-powered tools.

Bosch says the same about its detectors: Please note: for your own safety, after detection you should switch off the power supply completely before you start drilling.

Source: Bosch DIY, Better safe than sorry: take the time to check the walls before you start drilling. Checked 12 Oct 2026.

Studs behind plasterboard

A plasterboard wall usually hides a frame. Wickes: You can tell if you've got a plasterboard wall if it sounds hollow when you knock on it, but these walls are generally supported by a frame so there will be vertical and horizontal sections that feel a little more solid.

Vogel's gives the usual spacing: In most cases, it is recommended that both wooden and metal stud profiles are placed at a centre-to-centre (c.t.c.) distance of 600 mm, although in some cases it may be 450 mm. Vogel's: For wooden profiles, you check this by knocking on the wall until you find a place that sounds less hollow. For metal stud profiles, you use a pipe finder, which allows you to detect the metal profiles.

Hitting a timber stud is useful: B&Q says If you're drilling into a plasterboard wall, you can also check where the timber studs are. If you find a timber stud where you want to drill, you won't need to use a wall plug. Vogel's adds a caution about the frame itself: Please note: you can not be sure whether the upright profiles are correctly fixed to the floor or ceiling. If in doubt, we always recommend consulting an expert.

Sources: Wickes, Where do I start putting up a shelf?. Checked 12 Oct 2026; Vogel's, How to mount a TV on a plasterboard or hollow wall. Checked 12 Oct 2026; B&Q, How to fit wall plugs. Checked 12 Oct 2026.