The short answer
Use a detector that finds both timber and live wires, and assume there is a cable running vertically above and below every socket and switch and horizontally across from it.
- Use a multi-mode detector and sweep both horizontally and vertically over the whole area.
- Check it against a known stud first, so you know it is working.
- Avoid the safe zones in reverse: cables are permitted to run in a 150mm band from the top of a wall and from each internal corner, and in vertical and horizontal lines from any socket or switch. Treat those areas as occupied.
- Drill slowly and stop the moment resistance changes.
What will ruin it
Detectors are not infallible, especially with foil-backed plasterboard or in solid walls. If a fixing has to go somewhere risky, turn the circuit off at the consumer unit first.
Why it works
Wiring regulations define permitted cable routes precisely so that anyone can predict where a cable probably is. That prediction is more reliable than most cheap detectors.
Gas work requires Gas Safe registration by law and most electrical work is notifiable. Where a tip says to call somebody, that is the advice. Full disclaimer.
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