Home / Tools / Concrete Fire Resistance (IBC 722) H · Fire

Calculated Fire Resistance of Concrete — IBC §722.2

Fire-resistance rating of concrete walls, floors and roofs from the equivalent thickness (including ribbed panels), and of concrete columns from the least dimension and cover.

Wall, floor or roof

Aggregate

Minimum thickness t in

Rib spacing s (blank = flat slab) in

Net area over one spacing (projections beyond 2t excluded) in²

Column

Aggregate

Least dimension in

Required rating

Cover to main bars in

Results

Equivalent thickness te · rule—

Wall/floor rating (heat transmission)—

Column rating from size · required size · cover check—

IBC §722.2 · ACI 216.1 · PCI MNL-124Wall and column thickness tables from PCI Designer's Notebook DN-31 (based on MNL-124, which the IBC references; consistent with IBC Tables 722.2.1.1 and 722.2.4); ribbed-panel rule per IBC 722.2.1.2 / ACI 216.1 Eq. 2-1; §722.2.4.2 column cover. The 1½-hour wall values are verified only for sand-lightweight concrete — other 1½-hour wall ratings are not given (conservative).

VerifiedAll tabulated values and the ribbed-panel equation are tested; a 5 in siliceous wall gives 2 h, as quoted in code discussions.

Preliminary calculation tool. Final design requires the full text of the referenced standard (see the sources on this page) and review by a licensed PE.