Which statement about SFRM thickness testing is correct?

• A. A metal deck with a flat plate requires 4 thickness measurements.
• B. A drill bit is used for thickness testing low density SFRM.
• C. The lowest allowable thickness for a wide flange column with a 2 inch requirement is 1-1/2 inch.
• D. The maximum drying temperature for density testing is 130 degrees F.

Answer: (A)

In SFRM thickness testing, you verify that the spray-applied fireproofing actually meets the required thickness across the surface by taking multiple readings rather than relying on a single point. For a metal deck with a flat plate, four thickness measurements are used to capture how the coating lays down across the area—typically spaced in a simple square pattern or near the corners and one in the center. This sampling approach helps ensure there aren’t thin spots that could compromise fire resistance and allows you to confirm both the average thickness and the minimum thickness meet the specified value.

The other methods described don’t align with how thickness is typically assessed. Using a drill bit is not a standard thickness gauge for measuring SFRM; drilling is more about sampling material for density or other analyses, not mapping thickness. Minimum thickness values for columns or girders, like a 2-inch requirement with a stated 1-1/2 inch minimum, are design- and project-specific and not a universal rule. And density testing has its own procedure for drying temperatures that isn’t universally capped at 130 degrees F.