A beam requires a mil thickness of 65 mils for TFIFRM. What is the lowest allowable average mil thickness for the beam?

In fireproofing practices, the specified mil thickness is critical for ensuring adequate protection of structural elements, such as beams, against fire. When the requirement is set at 65 mils, this is typically the standard reference for the minimum protective coating necessary to achieve the desired fire rating and thermal performance.

The lowest allowable average mil thickness is often aligned with the specified requirement. Achieving an average of 65 mils means that the coating must maintain consistency to support the structural integrity in the event of exposure to fire conditions. A coating that meets this thickness ensures that the beam is effectively protected according to design specifications and regulatory standards.

Therefore, the correct answer of 65 mils signifies that the beam requires exactly the specified thickness to ensure fireproofing effectiveness. Any thinner average would potentially compromise the fire protection capability, which is why it is critical for the average thickness to at least meet the specified requirement.