Section 803.1/Interior Wall and Ceiling Finish
IBC 803 regulates interior wall and ceiling finish materials based on flame spread index and smoke-developed index, with required classes varying by occupancy, sprinkler protection, and location.
Interior wall and ceiling finishes must be classified by flame spread index (FSI) and smoke-developed index (SDI) tested per ASTM E84 or UL 723. Class A finish has a flame spread index of 0 to 25 and smoke-developed index of 0 to 450. Class B has FSI 26 to 75 and SDI 0 to 450. Class C has FSI 76 to 200 and SDI 0 to 450. Table 803.11 specifies the required class for interior finishes based on occupancy group and location within the building. Exit enclosures and exit passageways generally require Class A. Corridors require Class A or B depending on occupancy. Rooms and enclosed spaces generally permit Class A, B, or C. In buildings equipped with an automatic sprinkler system, the required finish class may be reduced by one class (Class A to B, or Class B to C) in specific locations.
Why this section exists
Interior finishes are one of the primary contributors to fire spread within buildings. Wall and ceiling materials with high flame spread ratings allow fire to travel rapidly across surfaces, filling corridors and exit paths with smoke and heat before occupants can evacuate. The flame spread index measures how fast fire travels across the material surface, while the smoke-developed index measures smoke production. The graduated requirements (Class A in exits, lower classes in rooms) reflect that fire growth must be most restricted along egress paths where occupants are most vulnerable.
What plan reviewers look for
Plan reviewers check the finish schedule and specifications for interior finish classifications. They verify that exit stairway enclosures, exit passageways, and corridors have finishes meeting the required class from Table 803.11 for the building's occupancy classification. They check that the sprinkler reduction is applied only where the building is fully sprinklered. They look for high-risk materials such as FRP panels, wood paneling, and acoustic treatments that may require specific FSI/SDI documentation.