Scan Before You Core: Hidden Concrete Risks for Contractors
Treat every core drill as a field-verification task, not a routine cut, because a few inches of concrete can hide rebar, post-tension cables, conduit and plumbing. That is the argument in an Oct. 14, 2026 Construction Executive article by Sofia Brown.
What the Article Says
The article says a strike can lead to injuries, structural concerns, damaged building systems, emergency shutdowns, repair work and delays for multiple trades. A damaged conduit can cause an electrical outage. A severed post-tension cable creates an immediate safety hazard and requires structural engineering review. Damaged reinforcement may need evaluation before work can continue. Even with no injury, one bad penetration can bring repair costs, stoppages, revised sequencing and difficult conversations with owners.
Drawings are the starting point, not the clearance. Structural and MEP drawings can show slab design, reinforcement patterns, tendon layouts and utility routes, and as-builts may show what was actually installed. But renovations, tenant improvements and past repairs can leave conditions that differ from the record set. Older buildings may have undocumented systems or abandoned utilities.
The piece also warns that a scan only clears the area it covered. A penetration moved several inches to dodge ductwork or framing may land in concrete nobody evaluated. On GPR, the article says results still need interpretation. Slab thickness, closely spaced reinforcement, concrete conditions and target depth can all affect signal quality, and some objects produce similar responses. A scan also does not determine whether an unidentified target is safe to cut.
Note the byline: Brown is a digital marketing associate at a GPR scanning company, per the author note (the link points to superiorgpr.com). The guidance reads as practical, but it comes from a vendor.
What It Means for Subcontractors
- Coring and sawing crews: Before scanning, define each penetration’s location, diameter and expected depth. If several locations are in play, put every one in the scan zone. Re-verify any location that moves, even by a few inches.
- Post-tensioned slabs: Identify the slab type, review the structural information and verify tendon locations before coring. If the hole conflicts with a tendon or other significant structural element, move it or send it to the design professional.
- Hold-point sign-off (our inference): The source says findings should go to the person authorizing the cut. A written sign-off at that point would make the handoff traceable and keep one crew from assuming another cleared the spot. Check whether your project or owner already requires a formal hold-point form or permit for penetrations.
- Scanning scope: Ask providers to name the exact slab areas, wall areas or penetration points covered. Require the operator to explain markings, likely targets, limitations and any uncertain locations, and to brief the superintendent, cutting crew and affected trades.
- Electrical, plumbing and low-voltage trades: Conduit, communications lines, plumbing and fire protection lines can all sit in the penetration zone. Share your as-builts and any reroutes before scanning, since the article notes conduit is sometimes rerouted during original construction.
- Cost of a strike: The source does not say who pays. It also does not cite a specific OSHA standard or compare scanning methods. Our inference: settle responsibility for repairs, shutdowns and resequencing in the subcontract and scope letter before the first core, since the article lists those as the typical consequences.
