What is the lowest allowable average mil thickness for a beam requiring 65 mils for TFIFRM?

The requirement for an average mil thickness of 65 mils for a beam indicates that this is the target thickness needed to achieve the necessary fire resistance. In fireproofing applications, the average thickness is important to ensure adequate protection against fire exposure.

Selecting 65 mils as the lowest allowable thickness means that it must meet or exceed the specified requirement precisely. Using a lower average thickness could compromise the performance of the fireproofing material, potentially putting the structure at risk during a fire event. Therefore, maintaining the average thickness at the specified level is essential for safety standards and compliance with fire resistance criteria.

This is why the correct answer reflects the requirement set for TFIFRM to ensure effective fire protection.