jar546
CBO
A recent code interpretation confirms that a fire-resistance-rated floor or ceiling assembly cannot be classified or used as a horizontal fire wall under the International Building Code (IBC), even if it has a listed fire-resistance rating.
The clarification, which applies to both the 2021 and 2024 editions of the IBC, addresses a common misconception: whether a fire-rated horizontal assembly—such as a floor/ceiling system—can be used to subdivide a multistory structure into separate buildings in the same way a vertical fire wall can.
The answer is no.
Per Section 706.2 of the 2021 IBC, a fire wall must maintain structural stability during a fire to the extent that construction on either side of the wall can collapse independently without bringing down the wall itself. This is a core principle of firewall design and function.
In the case of a horizontal assembly, such as a fire-rated floor/ceiling system between two stories, that requirement cannot be met. If the lower story collapses due to fire or other structural failure, the horizontal separation would also collapse—along with the upper stories above it. This would violate the IBC’s requirement that a fire wall remain standing and intact to preserve the fire separation between structures or portions of a structure.
Because of this fundamental difference in performance expectations, the ICC has made it clear that a fire-resistance-rated horizontal assembly cannot serve as a fire wall, and therefore cannot be used to create separate buildings within a multistory structure.
Design professionals and code officials should take this distinction seriously when evaluating separation requirements for multistory construction. While horizontal assemblies play a critical role in passive fire protection, they cannot fulfill the code-defined function of a fire wall. Only vertical assemblies that meet the structural integrity requirements of Section 706.2 may be classified and used as fire walls under the IBC.
The clarification, which applies to both the 2021 and 2024 editions of the IBC, addresses a common misconception: whether a fire-rated horizontal assembly—such as a floor/ceiling system—can be used to subdivide a multistory structure into separate buildings in the same way a vertical fire wall can.
The answer is no.
Per Section 706.2 of the 2021 IBC, a fire wall must maintain structural stability during a fire to the extent that construction on either side of the wall can collapse independently without bringing down the wall itself. This is a core principle of firewall design and function.
In the case of a horizontal assembly, such as a fire-rated floor/ceiling system between two stories, that requirement cannot be met. If the lower story collapses due to fire or other structural failure, the horizontal separation would also collapse—along with the upper stories above it. This would violate the IBC’s requirement that a fire wall remain standing and intact to preserve the fire separation between structures or portions of a structure.
Because of this fundamental difference in performance expectations, the ICC has made it clear that a fire-resistance-rated horizontal assembly cannot serve as a fire wall, and therefore cannot be used to create separate buildings within a multistory structure.
Design professionals and code officials should take this distinction seriously when evaluating separation requirements for multistory construction. While horizontal assemblies play a critical role in passive fire protection, they cannot fulfill the code-defined function of a fire wall. Only vertical assemblies that meet the structural integrity requirements of Section 706.2 may be classified and used as fire walls under the IBC.
