Concrete scanning vs X-ray. The honest 95/5 answer.

For locating and mapping rebar, yes — ±5 cm positional accuracy with reliable depth estimates, in minutes, from one side. X-ray's advantage is image-grade detail when multiple embeds crowd within centimetres of each other, which matters on a small minority of penetrations. On routine clearance work the technologies agree; one just costs several times more and empties the floor.

Radiography needs the film or detector on the far side of the concrete from the source. A slab poured on soil has no accessible far side — so X-ray is physically impossible there. GPR, reflecting energy from one surface, has no such constraint; slab-on-grade is its home turf.

GPR emits low-power radio-frequency energy — comparable to a phone or Wi-Fi router, orders of magnitude below any harm threshold and non-ionising by nature. No badges, no permits, no exclusion zones. X-ray uses ionising radiation that demands licensed handling and evacuated exposure areas.

When a critical penetration lands in genuinely congested embedment — layered mats, bundled conduits, anchors — and misidentification would be expensive or dangerous, with both faces accessible. That's the honest 5%. We flag it during the GPR survey rather than selling X-ray jobs we'd profit from elsewhere; we don't operate radiography and have no incentive to oversell it.

GPR distinguishes conduit from rebar by signature, depth, and spacing — but it cannot confirm whether a conduit is energised. Standard practice: anything identified as conduit is treated as live, and where confirmation matters we pair the scan with electromagnetic detection, which senses energised cables directly.

GPR: typically $350–$500 for a single-visit clearance scope, with multi-point TI scopes from $500–$1,500. X-ray: commonly several times that per shot once licensed crew, evacuation coordination, and processing are counted — and night/weekend premiums apply because occupied floors must empty. The cost gap is the main reason the 95/5 split exists.

GPR clears a core location in 15–30 minutes with marks on the slab before the crew finishes coffee. X-ray needs setup on both faces, exposure time, and image processing per location — and scheduling around an evacuation. For multi-point scopes the difference compounds from hours into days.