Code guides · IBC Chapter 7
Fire-resistance ratings
Fire-resistance is the dominant cost driver on assembly types. Pick the wrong rating and you've spec'd the wrong gypsum + framing combination — easy to fix on the takeoff, expensive to fix in the field.
Construction types & ratings (condensed)
- Type I-A: 3-hr structural frame, 2-hr exterior bearing
- Type I-B: 2-hr structural frame, 2-hr exterior bearing
- Type II-A: 1-hr structural frame, 1-hr exterior bearing
- Type II-B: noncombustible (no rating required for many elements)
- Type III-A: 1-hr exterior bearing, 1-hr interior bearing
- Type III-B: noncombustible exterior, no rating interior
- Type IV (Heavy Timber): 2-hr exterior, no interior rating
- Type V-A: 1-hr structural frame, 1-hr exterior bearing
- Type V-B: no rating required (most single-family)
UL / Warnock-Hersey assembly numbers
When the spec calls for a UL-rated assembly (e.g. UL U419 for a 1-hr non-bearing wall), the takeoff scopes the EXACT GWB layers, framing, and insulation that assembly requires. Substituting a thicker single-layer of GWB doesn't satisfy a 2-layer UL design.
Disclosure
This is a plain-English summary for estimating purposes. It is not a substitute for the actual code documents — review for AHJ-specific amendments. Adopted editions vary by jurisdiction; OmniTakeoff applies the edition declared on the project, not a hard-coded default.
Related
Other guides in the same area.
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