RCC Slab and Wall Scanning Before Coring or Cutting

Structural concrete scanning shares equipment with ground survey and almost nothing else. The material is known and uniform, targets are shallow, tolerance is measured in centimetres, and the consequence of error is a structural or electrical event rather than a wet trench. The technique is the same; the discipline is not.

Why clear zone matters as much as detection

Clients frequently ask what is inside the slab when the question they need answered is whether their proposed opening will fit. A 150 mm core needs 150 mm of clear concrete plus a working margin, and a position that clips a bar at its edge is as unusable as one centred on it. We check the opening rather than only reporting the contents, and where the intended position does not work we mark the nearest one that does, so a decision is available on the day rather than deferred to a meeting.

What is delivered

Direct marking on the structure in an agreed colour convention distinguishing reinforcement, conduits, sleeves and clear zones. Photographs of the marked area, sized and referenced so the work can be verified later. A marked-up structural drawing where multiple openings are involved, showing each cleared position. An explicit statement where a slab was too congested for a safe opening, because that is a finding rather than a failure. Cover depth to reinforcement where durability assessment is in scope.

Beyond the basics

Can you distinguish conduit from rebar? Usually, from depth, diameter and the pattern of returns. Where the distinction cannot be made confidently we say so.

Does slab thickness limit the scan? Only if it exceeds the antenna's useful range. On most building slabs the scan covers the full thickness.

How long does one opening take? On a simple slab, minutes. On a congested one, considerably longer, which is why the work is priced per opening rather than per metre.

Can you scan post-tensioned slabs? Yes, and it needs particular care — see our post-tension cable detection page, where that risk is set out in full.

Do you core as well as scan? We scan and mark. Coring is normally the client's contractor, which keeps the checking party separate from the cutting party.

Terms used on this page

Rebar mesh — the reinforcement grid inside concrete, whose spacing and cover the scan establishes. Cover — the depth of concrete over reinforcement, governing durability and safe coring depth. Two-directional scan — passes at right angles, required to resolve bars parallel to a single pass. Clear zone — the area around a proposed opening that must be free of embedded material. Congested slab — a structure with so much embedded material that no safe opening position exists.