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Where’s the Rebar?

Updated: Jan 31

Where’s the Rebar?

One Survey, three outputs to suit your budget and timescale!

Concrete reinforcement (rebar) is located in both ground slabs and within the walls of many buildings. With so many refurbishment projects underway, we are often asked ‘where is the rebar?’

SUMO uses high frequency Ground Penetrating (GPR) to locate these individual rebars, along with a cover meter which can estimate the diameter of the individual bars.

Data is either recorded and/or interpreted on site, depending on your requirement, budget and timescales, to produce 3 survey outputs…

1. Mark out survey 2. Mark out survey with basic reporting 3. Post processed Survey with full reporting.

Output 1: Mark Out Survey

A basic mark out survey is where a GPR survey is interpreted on site and the location of the rebar is marked in situ. A cover metre may also be used to estimate the depth to the rebar, which is also noted on site. Whether on walls, floors or columns, this method is ideal if intrusive work is planned shortly after the survey, meaning that the contractor knows exactly where to avoid when drilling.

There is no permanent record made and so this is only appropriate for the construction phase and not planning stages. This is the cheapest and quickest survey output available.

A mark out rebar survey

Above: A mark out rebar survey on a 3rd floor exterior wall, ahead of drilling for a secure platform. A crane and crane bucket were used to access the area.

Output 2: Mark out survey with basic reporting

This option is employed where intrusive work is scheduled soon after the survey, but the site is too complex to warrant a simple mark out survey. It also gives you a permanent record of what was surveyed at that time.

In the example below, a GPR survey was conducted over 6 columns on the fifth floor of a hospital in order to investigate reinforcing and understand the load bearing of the columns before constructing an additional floor above. The location of the surveyed columns was marked on site, then recorded on a digital plan, along with the position of the rebar within those columns.

Mark out survey with basic reporting

Above left image : Blue circles - surveyed column. Above right image : Column 029 - Reinforcement depth 45mm.

Output 3: Post processed survey with full reporting

A full desk-based analysis of the data and production of a full report is useful at the design and planning phase and/or the site is more complex.

In the example below, two layers of rebar have been located (inner mesh and outer mesh). The data is displayed both as radargram (section views of the data) and as a digital plan interpretation. The results indicate that the outer mesh has a cover depth range of 15 - 20mm and the internal, inner mesh cover depth is typically between 50 -70mm. Cover meter readings indicate that the both horizontal and vertical rebars of the outer mesh appear to have an indicative diameter of 7mm.

Section view of the GPR data

Above: Section view of the GPR data (Radargram) showing two layer of rebar.

Interpretation of rebar mesh, plotted in AutoCAD

Above: Interpretation of rebar mesh, plotted in AutoCAD.


Want to learn more?

Please pick up the phone and speak to Simon Haddrell or Richard Fleming who will happily suggest the right output for your site.

01684 592266

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