Why You Must Scan Concrete Before Drilling or Cutting
Striking a post-tension cable mid-drill takes less than a second. The consequences — catastrophic structural damage, site closures, injury, and remediation bills exceeding $500,000 — can take years to resolve. GPR scanning costs a fraction of that risk.
Industry Reality
Post-tension cable strikes are one of the most common and costly construction incidents in Australia. Many occur because GPR scanning was skipped to save time or money — a decision that almost always costs far more in the end.
What's Hidden Inside Concrete?
Modern concrete structures — particularly floors, slabs, and walls built from the 1980s onwards — contain a complex array of embedded elements that are completely invisible from the surface:
The Consequences of Striking a Post-Tension Cable
Post-tension cables are the highest-risk embedded element. These high-strength steel tendons are held under enormous tension — when struck, they can:
Immediate catastrophic deflection
A severed tendon releases stored energy explosively. The affected slab section can deflect dramatically within seconds, risking collapse.
Progressive structural failure
In unbonded post-tension systems, severing one cable redistributes load to adjacent tendons — potentially triggering a chain of failures across the slab.
Site shutdown and evacuation
Any suspected PT strike triggers immediate site closure, structural assessment, and WorkSafe investigation — halting the entire project.
Remediation costs of $100,000–$500,000+
Repairing post-tension damage requires specialist structural engineers, access scaffolding, temporary propping, and tendon replacement or supplementary reinforcing.
Legal and liability exposure
Contractors who drill without scanning face significant liability exposure to building owners, engineers of record, and injured parties.
How GPR Concrete Scanning Works
GPR concrete scanning is a non-invasive, non-destructive technology that uses electromagnetic pulses to map the internal structure of concrete elements in real time.
The GPR antenna is moved across the concrete surface in a grid pattern.
Electromagnetic pulses penetrate the concrete and reflect off embedded objects.
Reflected signals are processed to create a subsurface map showing location and depth of all embedded elements.
A technician marks safe drilling/cutting zones directly on the slab surface.
A report documenting findings is provided for project records.
A typical slab scan takes 30–90 minutes depending on area. The cost is a small fraction of the risk it eliminates.
Liability Implications for Structural Engineers
For structural engineers specifying or supervising work involving concrete penetrations, GPR concrete scanning is increasingly a professional due diligence requirement. Engineers who specify or approve core drilling or cutting works without requiring GPR pre-scanning may face professional liability exposure in the event of a strike.
Many Queensland structural engineering firms now include GPR concrete scanning Brisbane and GPR concrete scanning Gold Coast as mandatory prerequisites in their construction specifications and scope-of-work documents. We recommend all engineers adopt this practice.
Delco's GPR Scanning: What's Included
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