A commercial building inspector is reviewing plans for a new 5-story Group B office building of Type II-A construction. The plans indicate the use of a Class B flame spread index for interior wall and ceiling finishes in the corridors. Is this acceptable?
- AYes, but only if the building is fully sprinklered.
- BNo, corridors in Group B buildings always require a minimum Class C flame spread index.
- CNo, Class A flame spread index is always required for corridors in multi-story buildings.
- DYes, Class B is generally acceptable for corridors in sprinklered Group B buildings.
Show answer & explanationAnswer & explanation
Correct answer: D. Yes, Class B is generally acceptable for corridors in sprinklered Group B buildings.
According to IBC Table 803.11, for corridors in Group B occupancies, a Class B flame spread index is permitted for interior wall and ceiling finishes. The presence of an automatic sprinkler system may allow for further reductions or maintain the Class B requirement where Class A might otherwise be needed, but Class B is the standard for Group B corridors.
Why the other options are wrong
- A. While sprinklers can influence flame spread requirements, Class B is the base requirement for Group B corridors, and the question implicitly assumes a standard code application.
- B. Class C is typically permitted in general rooms/spaces or for lower hazard occupancies, not corridors in Group B buildings.
- C. Class A is required for corridors in certain high-hazard or institutional occupancies, but not 'always' for multi-story buildings.
Interior Finish Flame Spread Index (Corridors)
The flame spread index for interior finishes in corridors is a critical life safety requirement, controlling the rate at which flame spreads across surfaces during a fire. It is classified as Class A, B, or C, with Class A being the most fire-resistive, and varies based on occupancy group and location within the building.
- Controls flame spread rate.
- Class A, B, C ratings.
- Corridors are critical egress paths.
- Requirement depends on occupancy and sprinkler system (IBC Table 803.11).
Memory trick: The 'Finish Fire Check' ensures walls don't help fire run fast.