Elevated Floor Slab 3D Scanning: Ensuring Safe Demolition and Structural Confidence

Before any demolition or structural modification, understanding what’s inside a concrete slab is essential. For one construction team preparing to cut a new staircase opening in an elevated floor slab, uncertainty about interior reinforcement posed serious challenges:

• Unknown reinforcement layout

• Possibility of post tension cables or tendon systems

• Risk of cutting or coring into critical structural elements

Without accurate internal data, the contractor faced multiple high risk consequences. Cutting into a live post tension cable could cause violent recoils with potential for catastrophic injury, while accidental damage to primary reinforcement could compromise structural integrity. Additionally, unnecessary rework, schedule delays and cost overruns were imminent if crews encountered unknown subsurface conditions during demolition.

To mitigate these risks and provide construction and structural engineers with actionable information, the client engaged OmniVueNDT to perform an advanced 3D elevated floor slab scan. The image below shows the area marked for scanning, where the planned staircase opening would be cut. The blue boundary outlines the zone that required detailed 3D radar analysis to identify structural supports like joists, girders and beams, as well as all floor slab reinforcement and any post tension cables.

How OmniVueNDT Approached the Challenge

OmniVueNDT’s technicians began by conducting a thorough Ground Penetrating Radar (GPR) survey of the target slab area. Unlike conventional 2D scanning, which provides only planar slices, the 3D process captures depth information and structural geometry across the entire slab thickness.

Key steps included:

• Calibration of GPR equipment to the specific concrete thickness and expected reinforcement densities

• Systematic grid scanning of the marked staircase footprint

• Collection of high resolution radar scans in both longitudinal and transverse directions

• Time slice interpretation to visualize reinforcing bars (rebar), mesh layers and potential post tension cables at different depths

The scan results are visualized below in a plan view radar time slice. Each joist beneath the concrete slab appears as a distinct linear feature, color-coded for clarity. This 3D radar image reveals the spacing, orientation and depth of structural supports that were completely hidden from visual inspection.

The collected data was processed into a three dimensional model and cross referenced with a LiDAR based site capture to create a hybrid deliverable. OmniVueNDT scanned both the floor and the job site with a LiDAR scanner to recreate a virtual model of the space, capturing the real dimensions of the scanned area. The 3D radar image was then overlaid onto the LiDAR imagery, as shown below, providing the design and engineering team with a comprehensive information system that shows both the physical space and the hidden subsurface conditions with precision.

Deliverables That Drove Decision Making

OmniVueNDT provided the client with:

• 3D reinforcement maps illustrating rebar orientation, spacing and depth

• Post tension or tendon identification or confirmation of absence where present

• Time slice visualizations highlighting key depth layers within the slab

• Accurate measurements for joist spacing and slab thickness variations

Each structural element was clearly defined, enabling engineers to place reinforcements in their design models and contractors to map cutting paths that avoid hazards.

Why This Matters: Risk Avoidance and Project Assurance

Without this detailed subsurface intelligence, the contractor faced serious risks that could have resulted in:

• Safety hazards — Striking a tensioned cable could result in explosive force and severe injury

• Structural compromise — Damage to critical reinforcement could weaken the slab, requiring costly remediation

• Schedule impacts — Delays caused by unexpected obstructions and redesigns

• Budget overruns — Reactive field modifications inevitably increase costs

In contrast, with OmniVueNDT’s scanning and mapping data, the project team was able to:

• Plan precise cutting paths that avoided all primary reinforcement

• Provide structural engineers with accurate as built conditions for design integration

• Maintain schedule integrity with confidence and reduced uncertainty

The value of knowing what lies inside a structural slab before cutting cannot be overstated — it’s a proactive safeguard against risk, cost and loss.

Cut With Confidence, Design Without Risk

If your project involves demolition, coring, cutting or structural modification of concrete slabs, you can eliminate uncertainty with a comprehensive 3D scan. Contact OmniVueNDT today to secure the subsurface insight you need to protect your team and your schedule.