What's hiding in the slab
Most commercial slabs and many newer Texas homes are post-tensioned. Cutting a tensioned cable is dangerous and expensive to repair. Slabs can also hold rebar, electrical conduit, plumbing, radiant tubing and voids.
The checklist
- Mark every core and cut location on the slab before the scan.
- Confirm whether the slab is post-tensioned (look for stamps or ask the building engineer).
- Scan both sides of elevated decks where possible.
- Have the scan results marked directly on the concrete, not just in a report.
- Keep a clearance buffer from marked cables and conduit.
- Scan again if locations move.
How GPR scanning works
Ground-penetrating radar sends pulses into the concrete and records reflections from anything that differs from the surrounding concrete: steel, conduit or voids. A trained technician reads the data on site and marks locations and depths on the surface.
Questions
Can GPR tell post-tension cables from rebar?
An experienced technician can often tell them apart by pattern, depth and profile, and marks them accordingly.
How deep can concrete scanning see?
It depends on the concrete and equipment, but typical slab scanning covers the depths where tendons, rebar and conduit sit.