Concrete scanning is a loose term which covers a range of non-destructive techniques to establish detail within the concrete subsurface. It is much more than just rebar location.

A range of survey techniques can be used, including, but not limited to:

  • Ground Penetrating Radar (GPR)
  • Ferroscan
  • Cover Meter
  • Ultrasound
  • Impact echo

All these techniques penetrate the concrete surface and can locate objects and anomalies. Each has advantages and disadvantages and work within specific depth ranges.

In this article, we concentrate on GPR scanning; however, references are made to the other techniques.

GPR Concrete scanning

Concrete scanning of column using GPR
Concrete scanning using GPR

Sandberg specialises in the use of Ground Penetrating Radar concrete scanning within the construction and Civil Engineering industries.

GPR is arguably the best technique for scanning concrete. It offers deeper penetration than Ferroscan, and the Cover Meter, better resolution and its detection is not limited to metallic objects. It works by detecting changes in the subsurface and can detect most materials including plastic, wood and voids. Find out more about how GPR works.

The term “ concrete scanning” is often used to describe the detection of reinforcing steel (rebar) in concrete; however, it covers much more. Read on to see what it does cover:

Rebar location

Concrete scanning is probably most commonly used for rebar location. It is essential to locate reinforcement and other features in concrete before cutting or drilling. In most cases, the surveyor only scans the area where the intrusive works will be carried out, marking up detected rebar, and other features in-situ. In this type of scenario, it is not necessary to determine the full distribution of the reinforcement.

Find out more about rebar location and site mark-up surveys.

Rebar mapping

Schematic representation of concrete scanning using GPR for rebar mapping
GPR concrete scanning can map several layers of reinforcement

Rebar mapping describes more detailed surveys to determine reinforcement distribution. They can take several different forms:

  1. Determine the general rebar distribution, including the number of reinforcement layers and bar centres.
  2. Identify variations in rebar distribution and changes in construction.
  3. Determine the position of every bar and plot their position in CAD.

Rebar mapping is often undertaken as part of structural analysis, e.g. to determine load capacity, or to verify as-built drawings.

Find out more about rebar mapping surveys.

Concrete imaging

Although concrete imaging often includes rebar location or rebar mapping, it does not necessarily have to be reinforced concrete. It can include imaging of construction details such as mass concrete, reinforced concrete (slabs, beams and columns), concrete thickness, clay pot construction, precast concrete planks, screed layers formed voids and detection of insulation layers.

Radargram showing detected reinforcement and construction detail
GPR concrete scanning used to image a suspended concrete slab. The dashed pink line indicates a screed/concrete interface, the top rebar is indicated by red dots, bottom rebar indicated by green dots, the underside of the slab is indicated by the solid yellow line and a down-stand beam by the dashed yellow line.

Tendon location

Whether you need to locate tendons to asses their condition, verify their presence, or accurately locate them before cutting or drilling concrete, GPR is probably the most reliable concrete scanning method for detecting tendons.

Tendons can be deep and are usually behind a layer of reinforcement, which can be dense, particularly near anchors. Consequently, most other techniques can’t detect them.

Find out more about GPR concrete scanning to locate tendon ducts.

Underfloor heating pipes

Underfloor heating pipes are nearly always plastic. Consequently, a cover meter and Ferroscan are unable to detect them. On the other hand, GPR provides a fast and efficient NDT means of locating underfloor heating pipes. It can detect and locate both metal and plastic pipes.

Underfloor heating pipes being covered with screed
GPR can detect plastic underfloor heating pipes

Find out more about locating underfloor heating pipes.

Thickness surveys

GPR can provide thickness readings for concrete slabs, screeds, walls, road construction, etc. Variations in thickness and construction detail can also be detected. Typically, only one-sided access is required.

Find out more about wall and slab thickness measurement.


The term concrete scanning covers a wide range of concrete scanning applications. We have seen that Ground Penetrating Radar is a very capable concrete scanning technique. It is very flexible and suitable for most concrete scanning applications. It is also non-destructive.

N.B. Although this article is about concrete scanning, GPR is not limited to scanning concrete. It is equally suitable for scanning brickwork, asphalt, screed, mortar, plaster and many more materials.

Need more information?

Contact our GPR experts to find out more about concrete scanning and also how our surveys could help you. Our experts will be happy to advise you about the most suitable survey methods for your specific requirements.

Telephone: 0207 565 7056