Post-Tension Cable Detection: Why GPR is the Safer Way to Scan
When your project involves coring, cutting or anchoring into concrete slabs, understanding what’s hidden inside that concrete is critical - especially when post-tension cables are involved. These high-strength steel cables are crucial to structural integrity and damaging one can lead to catastrophic failure, worker injury or costly delays. That’s why more construction teams are relying on Ground Penetrating Radar (GPR) to make sure they’re working smart - and safe.
At OmniVueNDT, we’ve completed hundreds of scans across commercial office buildings, parking garages and elevated slab structures to detect and map post-tension cable layouts. Our GPR specialists are often brought in before any penetrations are made, giving the crew a clear go/no-go map that allows them to work with confidence.
Understanding the Risk
Post-tension cables are often installed in a stressed condition within concrete slabs to improve structural performance while reducing material weight. However, they’re also under extreme tension - upwards of 33,000 pounds. Accidentally severing one during drilling doesn’t just risk the structural stability of the slab - it also puts workers in danger of cable whiplash or concrete blowout.
Contractors who rely solely on outdated drawings or assumptions from similar buildings are playing a dangerous game. We’ve seen it firsthand: discrepancies in design documents, unknown retrofits and poorly marked systems can leave even experienced teams at risk.
How GPR Works in the Field
GPR technology uses radar pulses to detect changes in material density beneath the surface. Post-tension cables show up as high-amplitude, hyperbolic reflections in the scan. Our team interprets this data on-site in real time, marking cable locations directly onto the surface or compiling detailed mapping reports upon request.
What sets OmniVueNDT apart is our methodical approach. We typically scan in two directions - perpendicular and parallel to the likely cable orientation - to ensure full coverage and detect any intersecting objects such as electrical conduit or rebar. Our team also cross-verifies findings with existing plans and client objectives to align safety and scope.
Real-World Success
In a recent project, we scanned six floors of a commercial tower scheduled for a full mechanical system upgrade. The original plans showed a standard cable layout, but our scans told a different story. We discovered irregular spacing near beam pockets and identified embedded conduits passing between cable layers - information the facilities team hadn’t accounted for. Thanks to the GPR survey, the client adjusted their coring plan and avoided damaging critical components.
Peace of Mind Before You Drill
Post-tension cable detection isn’t just about compliance - it’s about protecting your workers, your timeline and the integrity of your build. If you’re planning to modify a post-tensioned slab, GPR is a low-risk, high-reward investment.
Partner with OmniVueNDT for fast, reliable and accurate scanning before your next critical cut.