Ground penetrating radar (GPR) concrete scanning is the most reliable non-destructive method for locating rebar, post-tensioned cables, conduits, voids, and other embedded objects within concrete structures before you drill, core, or cut.
NDTScan is a specialist GPR concrete scanning company based in Oxford, serving construction, civil engineering, and infrastructure clients across a 100-mile radius including London, Birmingham, Bristol, Reading, Milton Keynes, and Cambridge.
What GPR Concrete Scanning Detects
GPR works by transmitting electromagnetic pulses into the concrete surface and recording reflected signals from subsurface objects and interfaces. A trained operator using specialist processing software can identify and map the following:
- Rebar and mesh location and depth — accurate to ±10mm in normal conditions
- Post-tensioned cables and tendon ducts — critical for safe coring in PT slabs
- Conduits and embedded services — electrical, data, heating pipes within slabs
- Slab thickness — where accessible from one side only
- Cover depth to reinforcement — supporting structural assessment and carbonation surveys
- Voids and delamination — loss of substrate contact, particularly in overlaid slabs
- RAAC (Reinforced Autoclaved Aerated Concrete) — detection and mapping of this problematic structural material
Standards and Methodology
All GPR scanning is conducted to the principles set out in BS EN 12504 (testing concrete in structures) and CIRIA C748 (safe intrusive investigation of structures). Pre-drill and pre-core scanning follows the methodology recommended by the Concrete Society and the UK Concrete Scanning Standards (UKCSS). Reports are formatted for engineering acceptance and include annotated site plans, depth data tables, and photographic records.
When Do You Need GPR Concrete Scanning?
- Pre-drill and pre-core surveys — mandatory on post-tensioned structures, strongly recommended on all reinforced concrete
- Structural assessment — when rebar configuration, spacing, or depth is unknown or undocumented
- Refurbishment and fit-out — before fixing through floors, walls, or ceilings
- RAAC surveys — school, hospital, and public building stock built 1950–1990
- Void investigation — where settlement or delamination is suspected beneath a slab
- Cover depth surveys — combined with half-cell potential and carbonation testing for a full concrete condition report
Equipment We Use
NDTScan operates GSSI SIR and Mala GPR systems alongside Hilti PS ferroscan equipment, providing complementary verification of rebar location data. All equipment is maintained and calibrated to manufacturer specifications.
What the Report Includes
Every GPR concrete scanning report includes: scaled annotated plan drawings showing all detected targets, depth measurements for each identified feature, photographic site record, equipment details and calibration confirmation, and a written interpretation statement. Reports are issued in PDF and DWG formats as standard.
Coverage Area
Based in Oxford, NDTScan provides GPR concrete scanning services across a 100-mile operational radius including: London, Birmingham, Bristol, Reading, Swindon, Milton Keynes, Northampton, Cambridge, Luton, Southampton, and Gloucester.
Frequently Asked Questions
How deep does GPR penetrate into concrete?
Typical penetration depth in reinforced concrete is 300–500mm, depending on reinforcement density, moisture content, and antenna frequency. In low-loss conditions, penetration can reach 600–800mm.
Can GPR locate post-tensioned cables?
Yes. GPR is one of the most reliable methods for locating post-tensioned tendon ducts in slabs and beams. Pre-core scanning on PT structures is critical — a tendon strike can cause structural failure.
What is the minimum area you can scan?
There is no defined minimum area. We conduct targeted pre-drill scans on single fixing points as well as full-floor surveys covering thousands of square metres.
How long does a concrete GPR scan take?
A typical pre-drill survey for 10–20 fixing positions takes 1–2 hours on site. A full floor plate scan of 500m² takes approximately half a day including data processing.
Do I need to prepare the surface before scanning?
In most cases, no. GPR can be conducted on standard concrete finishes, screed, and many types of floor covering.