Two things you cannot see in a wall without a special device — electrical cables and pipes. A detector is one of those tools that costs relatively little but can save you from a serious accident or an expensive repair. Here’s how to use it properly.
Types of Detectors — What’s the Difference
Three main types are on the market:
- Cable / wire detector — locates live and dead cables via electromagnetic field or induction.
- Metal detector — finds metal pipes, rebar, anchors, and screws inside walls.
- Moisture meter — measures the moisture content of a material by resistance (pin method) or electromagnetic wave (pinless method).
Most mid-range consumer devices combine two or three of these functions. Professional models (Bosch D-tect, Leica) cost more but are significantly more accurate — that’s what our technicians carry on the job.
Using a Wire Detector — Step by Step
Safety note: even with a detector, exercise caution when drilling. The device shows approximate location — not millimetre precision.
- Step 1. Hold the detector flat against the wall. Don’t press too hard — it can distort the reading.
- Step 2. Move slowly in horizontal passes, scanning from floor to ceiling in 20–30 cm bands.
- Step 3. When the device signals (beep, LED, vibration) — mark the boundary points on both sides with a pencil. The centre between marks is the centre of the obstacle.
- Step 4. Repeat the scan vertically (top to bottom) and compare results.
- Step 5. Only after two scans, mark a safe drilling point — at least 5 cm from the signal centre.
Using a Moisture Meter
- Pin method (contact) — two probes are pushed into the material. Immediate reading, leaves small marks. Best for timber and plaster.
- Pinless method (induction) — held against the surface, no damage to the material. Less precise, but excellent for quick screening of large areas.
Reference moisture levels for timber: dry below 15%, acceptable 15–20%, wet above 20%. For concrete and plaster the scales differ — check the manual for your specific device.
Common Mistakes When Using a Detector
- Scanning in one direction only — a cable can run diagonally.
- Dismissing a signal in a partition wall — in older Warsaw buildings, pipes are often routed through partition walls.
- Trusting a single reading — always scan at least twice.
- Drilling immediately after a signal — mark, compare, find the safe spot first.
When a Detector Is Not Enough
Consumer-grade detectors have limited penetration depth — typically 3–5 cm. In thick reinforced-concrete walls common in older Warsaw blocks, readings can be unreliable. If you have doubts before a larger drilling job, order a professional survey — our equipment can show a cross-section of the wall without damaging it. Leave a request via the form on this page and we’ll get back to you with details.