Don’t take chances. Locate concrete reinforcing steel before you find it with your drill bit, core barrel or saw. Work safe!

You should always check any concrete for reinforcing steel and other embedded objects before cutting, drilling, sawing or other intrusive works. Whether it’s a concrete slab, beam, column, wall, foundation, footing, retaining wall, pavement, etc., check first!

It’s not only about locating concrete reinforcing steel; it also applies to post-tensioned tendons, prestressing strands, conduits, and services. N.B. It’s not always metallic; it could be glass fibre reinforcement, fibre-optic cables, or plastic pipes.

Why you must locate reinforcing steel

In most cases, professionals are looking for rebar, conduits and post-tension cables to avoid them when cutting or coring concrete. Failure to do so could result in the following:

  • Injuries
  • Damaged equipment
  • Structural problems
  • Delays
  • Additional costs

Determining reinforcing steel distribution, depth of cover and tendon location/profile could also be required for construction verification purposes, structural analysis or materials testing.

There are two main methods of locating rebar and other embedded objects in concrete:

Electromagnetic Methods

Electromagnetic induction methods are relatively low-cost and straightforward; therefore, most rebar detectors are based on this principle. These rebar detectors, commonly referred to as covermeters, range from simple rebar locators to more advanced instruments, such as the Hilti Ferroscan, which will map reinforcement within a scanned area and provide estimates of rebar diameter. – For a more detailed comparison, see our article about Ferroscan and GPR rebar mapping surveys.

Pros and cons

  • Relatively low cost and easy to use
  • Advanced models will provide rebar diameter estimates
  • Systems such as the Ferroscam can produce images of the reinforcement
  • Limited depth penetration, typically <100 mm
  • Usually limited to a single rebar layer
  • Generally suitable for small areas only
  • Detects metal only; will not detect non-metallic materials such as plastic, voids, etc.

Ground Penetrating Radar (GPR) Methods

GPR is our preferred method of rebar mapping and concrete imaging. It uses pulses of electromagnetic radiation to image the subsurface and detect changes in material types rather than specific materials. Find out more about how Ground Penetrating Radar works.

Schematic representation of Ground Penetrating radar being used for rebar mapping to locate two reinforcing layers.
High-resolution rebar mapping using GPR

The advantages of GPR include the following:

  • Penetration depth up to ~450 mm (greater depths are possible but at lower resolution).
  • GPR can usually resolve two layers of reinforcement.
  • Suitable for small local areas or large area.
  • Simple location surveys can be interpreted in real-time and marked-up on-site. More advanced analysis and interpretation can be undertaken by saving the data and processing it off-site.
  • Post-processing can produce pseudo images and models.
  • Detects metallic and non-metallic objects (so will detect rebar, tendons, fibre-optic cables, plastic, etc.)
  • Can determine slab and screed thickness.
Radargram showing detected reinforcement and construction detail
Radargram image showing section view through slab/beam. The dashed purple line indicates the screed/concrete interface, red dots highlight the top rebar, and green dots highlight the bottom rebar. The yellow line indicates the underside of the slab, and the dashed yellow line indicates a down-stand beam.

GPR also has some limitations and disadvantages:

  • GPR will not determine rebar diameter
  • It can be more expensive
  • Easy-to-use all-in-one systems are available, but for best results, we recommend an experienced operator carries out GPR surveys.