List two common non-destructive test methods for verifying thickness of fireproofing.

• A. Destructive core sampling.
• B. Ultrasonic testing and x-ray.
• C. Visual inspection and moisture measurement.
• D. Calibrated gauges and point measurements across the surface; use of thickness meters.

Answer: (D)

Non-destructive verification of fireproofing thickness relies on getting direct readings from the installed coating without removing material. Two common approaches are using calibrated gauges and thickness meters to take point measurements across the surface. Calibrated gauges let you compare the coating against known thickness standards by placing the gauge on the surface and reading the reference marks, which is quick and straightforward for field checks. Thickness meters provide numeric readings at a given spot, and you can repeat measurements across the area to map variation and ensure the coating meets the required thickness. This combination is practical for on-site inspection, covers irregular surfaces, and avoids damaging the coating.

Other methods either involve removing material (destructive core sampling) or rely on inspection alone or more specialized techniques that aren’t as routinely used for quick field thickness checks.