What is the minimum thickness measurement for SFRM on a metal deck with flat plate?

The minimum thickness measurement for Spray-Applied Fire-Resistive Material (SFRM) on a metal deck with a flat plate is indeed 4 inches. This requirement is established to ensure adequate fire resistance, as the thickness of the fireproofing material is critical in achieving the necessary performance during a fire scenario.

In the context of fire resistance ratings, thicker application of SFRM typically enhances the structural integrity of steel elements by providing greater insulation against heat. This helps prevent steel from reaching critical temperatures that could lead to structural failure. The requirement of 4 inches ensures that the fireproofing can adequately perform its intended function in protecting the steel deck from high temperatures during a fire.

Other options imply thicknesses that do not meet the established code requirements or may not provide sufficient protection in fire scenarios, thus highlighting the importance of adhering to the minimum thickness as prescribed by the relevant codes and standards.