Rebar location

Rebar in concrete
Don't take chances. Locate rebar in concrete before you find it with your drill bit, core barrel or saw!

You should always check any concrete for rebar 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 usually rebar that you need to locate in concrete, but, 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, fibreoptic cables or plastic pipes.

Why you should locate rebar

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:

  • Injuries
  • Damaged equipment
  • Structural problems
  • Delays

Determining rebar 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 operation; therefore, most rebar detectors are based on this principle These rebar detectors, commonly referred to as Covemeters 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 <100mm
  • 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 location and mapping. It uses pulses of electromagnetic radiation to image the subsurface and detects changes in material types, rather than specific materials. You can find more information about GPR, including how it works, on our Ground Penetrating Radar page.

Click images to enlarge.

  • GPR used to locate rebar
  • GPR can locate and map two layers of rebar
  • GPR radargram showing detected rebar in floor slab at down-stand beam location.

Pros and cons

  • Penetration depth up to ~450mm (greater depths are possible, but at lower resolution)
  • Can usually resolve two layers of reinforcement
  • Suitable for small local areas or large area
  • Simple location surveys can be interpreted in real time. More advanced analysis and interpretation can be undertaken by saving the data and processing the it off-site
  • Can produce 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
  • Will not determine rebar diameter
  • More expensive
  • Easy to use all in one systems are available, but for best results we recommend GPR surveys are carried out by an experienced operator.

Rebar location surveys

To find out more, or to book a survey, please see the following:

Rebar mapping and concrete imaging surveys

Locating Tendon Ducts in Post-Tensioned Concrete

Locating services and conduits in concrete slabs