Hanging a TV bracket, fitting shelves or mounting a boiler controller all start with the same question: what is behind the wall? A stud finder (also called a wall scanner or wall detector) helps you locate timber studs and joists for a secure fixing, and many models also warn you about metal pipes and live cables. This guide explains how to use a stud finder properly, how to read the results and how to avoid the mistakes that lead to a drill through a cable.
What a Stud Finder Detects
Most modern stud finders work by sensing changes in density or electrical properties through the wall surface. Depending on the model and mode, they can detect:
- Timber studs and joists in plasterboard (drywall) partitions and ceilings.
- Metal such as steel studs, pipes, rebar and fixings.
- Live AC wiring carrying mains voltage.
Each detector has its own maximum depth for each material, so always check the specification. Detection depth through solid brick, dense plaster or tiled walls is usually lower than through plasterboard.
Before You Start
- Charge or replace the battery. A low battery is a common cause of unreliable readings.
- Clear the area. Take off pictures and move away from metal objects, and keep your other hand off the wall while scanning.
- Know your wall type. UK homes have a mix of stud partitions, solid masonry and dot-and-dab plasterboard on block. Dot-and-dab adhesive blobs can look like studs, so be prepared to double-check.
How to Use a Stud Finder: Step by Step
- Choose the mode. Select wood/stud mode to find timber, metal mode for pipes and steel, or cable mode for live wiring. Some scanners offer a shallow and a deep wood mode; start with the shallow mode on standard plasterboard.
- Calibrate on a clear spot. Place the scanner flat on the wall where you believe there is nothing behind it, then switch it on or press the scan button. Hold it still until it is ready. Calibrating over a stud will give false results.
- Slide slowly and flat. Move the scanner horizontally across the wall at a steady pace, keeping it pressed flat. Do not tilt or lift it.
- Watch for the signal. As you approach an object, the display and indicator change. When it shows the centre of the target, stop.
- Mark both edges. Mark the point where the signal starts, then scan from the other direction and mark again. The centre of the stud is between the two marks.
- Confirm vertically. Scan up and down along the marked line. A stud runs vertically; a short, isolated reading may be a nail, a pipe clip or an adhesive blob.
- Switch to metal and cable modes. Before drilling, re-scan the same area for pipes and live wiring.
Reading the Results
Studs in UK stud walls are commonly spaced at regular centres, so once you find one, measure across to find the next and confirm it with the scanner. If readings appear everywhere, recalibrate on a different spot or switch to the deep mode. If nothing appears at all on a solid wall, it may simply be masonry, where you fix with wall plugs rather than into a stud.
Safety: Cables and Pipes
A stud finder is a useful aid, but it is not a guarantee. Keep these habits:
- Respect safe zones. In the UK, cables are typically run vertically or horizontally from sockets, switches and other accessories. Avoid drilling directly above, below or beside them.
- Cable detection needs live current. Live-wire modes generally detect energised AC cables. A switched-off circuit or a cable in metal conduit may not be detected.
- Isolate where in doubt. If you are drilling close to a likely cable route, switch off the circuit at the consumer unit first.
- Use a depth stop on your drill so you do not go deeper than needed.
Common Mistakes
- Calibrating over a stud or pipe.
- Moving too quickly, or tilting the scanner.
- Trusting a single reading without scanning from both sides.
- Forgetting to check for cables and pipes after finding the stud.
Stud Finders at EkoDeluxe
- FNIRSI WD-01 Wall Stud and Wire Detector: a rechargeable wall scanner with metal, cable and wood modes. Its LCD shows target depth, centre and material, backed by a coloured indicator and beep, and a centre positioning hole lets you mark the drilling point straight after a scan. Stated maximum depths are 120 mm for ferrous metal, 100 mm for copper, 50 mm for live AC wire and 20 mm (Exact mode) or 38 mm (Deep mode) for wood. It charges via USB Type-C.
Frequently Asked Questions
How accurate is a stud finder?
Accuracy depends on wall type, moisture, mode and calibration. Scanning from both sides and checking vertically gives the most reliable result.
Why does my stud finder beep everywhere?
It was probably calibrated over an object, or the wall is dense or damp. Move to a clear spot, recalibrate and scan again slowly.
Can a stud finder detect live wires?
Many can, in a dedicated cable mode, but usually only when the cable is energised. Always follow safe-zone rules and isolate the circuit if in doubt.
Does a stud finder work on brick or plaster walls?
It can detect metal and live cables in solid walls within its stated depth, but there are no timber studs to find in solid masonry. Use wall plugs for fixings.
How do I find the centre of a stud?
Mark where the signal begins from the left and from the right. The centre of the stud is halfway between the two marks.
Cover photo: “Man Drilling in Wall” by Lisa Fotios, free to use under the Pexels License, via Pexels. Cropped.
