What Is GPR Concrete Scanning?
Complete 2026 Guide for Engineers & Builders
Ground Penetrating Radar (GPR) concrete scanning is the industry-standard non-destructive method for mapping everything embedded inside concrete structures — before a single drill or blade touches the surface. At Delco Industries, we've performed over 5,000 GPR concrete scanning engagements across Gold Coast, Brisbane, and South East Queensland.
Quick Answer
GPR concrete scanning uses radar pulses to create a subsurface map of embedded objects inside concrete — including rebar, post-tension cables, conduits, and voids — without any cutting or drilling. It is used to prevent dangerous and costly strikes before penetrative work begins. In Queensland, Delco Industries performs GPR scanning with ±5mm accuracy and same-day engineer-certified reporting.
How Does GPR Concrete Scanning Work?
A GPR scanner emits short pulses of electromagnetic energy (radar) into the concrete surface. When these pulses hit a material with a different dielectric constant — steel rebar, a plastic conduit, an air void, or a post-tension cable — part of the signal reflects back to the antenna. The time it takes for that reflected signal to return determines the depth of the object. The strength of the reflection indicates the material type.
Modern GPR systems like those used by Delco Industries operate at frequencies between 400MHz and 2.6GHz, achieving depth penetration up to 600mm (and beyond in dry concrete) with accuracy of ±5mm in ideal conditions.
GPR Scanning Process — Step by Step
- 1Site Preparation: The scanning area is cleared and measured. The GPR antenna is calibrated to the concrete type, density, and thickness. Delco technicians assess moisture content and slab type before scanning begins.
- 2Grid Scanning: The antenna moves across the surface in a systematic grid pattern — typically 150–300mm line spacing — generating hundreds of scan lines across the target area.
- 3Data Interpretation: Raw hyperbolic reflections are identified and converted to precise object positions and depths. Delco's structural engineering team — not just technicians — interprets every scan.
- 4On-Site Mark-Up: Embedded elements are marked directly on the concrete with chalk or paint — showing safe and unsafe drilling/cutting zones, with depths noted.
- 5Report Delivery: A certified report with plan drawings, depth data, photographic documentation, and engineer sign-off — delivered same day or within 24 hours. Accepted by all QLD councils.
What Can GPR Concrete Scanning Detect?
Post-tension (PT) cables
Critical — severing causes structural collapse and serious injury
Reinforcing steel (rebar)
High — structural damage and project delays
Electrical conduits & cables
High — electrocution risk
Plumbing & hydraulic pipes
High — flooding and damage
Voids & honeycombing
Structural integrity compromise
Prestressed tendons
Critical in bridges and car parks
Drainage pipes
Service disruption and damage costs
Data/communications conduits
Business interruption
What GPR Scanning Cannot Detect
- → Objects in heavily saturated concrete (water attenuates radar signals)
- → Very thin objects smaller than the antenna's resolution (~5–10mm)
- → Objects beyond the system's penetration range (typically 600–900mm in dense reinforced concrete)
- → Metallic objects directly beneath other metallic objects (shadowing effect)
Delco's team always advises which areas are high-confidence and where supplementary methods (X-ray or acoustic testing) may be appropriate.
GPR vs Traditional Methods
| Feature | GPR Scanning | Rebar Locator | Concrete X-Ray |
|---|---|---|---|
| Detects post-tension cables | ✅ Yes | ❌ No | ✅ Yes |
| Detects plastic conduits | ✅ Yes (good conditions) | ❌ No | ✅ Yes |
| Detects voids | ✅ Yes | ❌ No | ✅ Yes |
| Depth accuracy | ✅ ±5mm | ⚠️ ±20–50mm | ✅ ±2mm |
| 3D subsurface map | ✅ Yes | ❌ No | ❌ No |
| Safe for occupied buildings | ✅ Yes | ✅ Yes | ❌ No (radiation) |
| Same-day results | ✅ Yes | ✅ Yes | ❌ No |
| BIM-ready data export | ✅ Yes | ❌ No | ⚠️ Limited |
| Typical cost | $$ | $ | $$$$ |
When Is GPR Concrete Scanning Required in Queensland?
Under the Work Health and Safety Act 2011 (Queensland), you are legally required to identify all hazards before penetrative work. GPR scanning is the industry-accepted method. It is required or strongly recommended:
- → Before any core drilling — even a single 50mm hole
- → Before concrete cutting or sawing — floors, walls, or structural elements
- → Before excavation adjacent to or beneath concrete structures
- → Pre-demolition surveys to identify embedded services
- → Before anchor or bolt installation into concrete
- → Post-tension and prestressed slab renovations — critical structural failure risk
- → Heritage building investigations — where drawings are unavailable or unreliable
- → Tunnel and underground structure assessments
How Much Does GPR Concrete Scanning Cost in Queensland?
Free, fixed-price quotes within 2 hours. The cost of a GPR scan is always a fraction of the cost of striking a post-tension cable — one strike can cost $50,000–$400,000 in remediation, not counting safety incidents.
Darren Lee — Director, Delco Industries
25+ years structural and civil engineering experience. 5,000+ GPR concrete scanning and NDT projects across Queensland and internationally. Specialist in GPR scanning, pile integrity testing, NDT structural analysis, and concrete assessment.
Related Services
GPR Concrete Scanning — Frequently Asked Questions
GPR stands for Ground Penetrating Radar. It refers to a geophysical method that uses radar pulses to image the subsurface of a material — in this case, concrete — detecting embedded objects such as rebar, post-tension cables, conduits, and voids.
Need GPR Scanning in Gold Coast or Brisbane?
Free quote within 2 hours. Same-week site visits. Engineer-certified reports accepted by all Queensland structural engineering firms.
Delco Industries — GPR Concrete Scanning specialists serving Gold Coast, Brisbane, Sunshine Coast, and all of South East Queensland. ABN 70 169 258 128.