Section 722.1/Calculated Fire Resistance
IBC 722 permits fire-resistance ratings to be determined by calculation methods in addition to standard fire test (ASTM E119), covering concrete, steel, wood, and masonry assemblies.
IBC 722 provides calculation methods for determining fire-resistance ratings as an alternative to laboratory testing per ASTM E119. Section 722.2 covers concrete assemblies, where the rating is based on the equivalent thickness of concrete and the type of aggregate. Section 722.3 covers steel assemblies, where the rating is based on the weight-to-heated-perimeter ratio (W/D) and spray-applied fireproofing thickness. Section 722.5 covers wood assemblies using the component additive method (CAM), which sums contributions of the membrane (gypsum board), framing, and insulation. Section 722.4 covers masonry. These calculated ratings are used when the actual assembly does not exactly match a tested design, allowing the designer to demonstrate compliance through engineering analysis referenced to Table 601 requirements.
Why this section exists
Standard fire tests are expensive and test only specific assemblies. When an actual construction assembly differs from a tested design, calculated fire resistance provides a code-compliant path to demonstrate the required rating without retesting. For concrete, the critical factor is heat transmission through the material thickness. For steel, the critical factor is the time to reach the critical temperature (1000 degrees F for columns, 1100 degrees F for beams) based on the mass of steel relative to the exposed surface area.
What plan reviewers look for
Plan reviewers check the construction type and verify that fire-resistance-rated assemblies are documented with either a tested design (UL design number, GA manual number) or a calculated rating per Section 722. For concrete assemblies, they check the equivalent thickness against Table 722.2.1.1 for the aggregate type. For steel, they verify the W/D ratio and fireproofing thickness. For wood, they check the component additive method against Table 722.5.1.