Reading Table 803.13
IBC Table 803.13 sets the minimum interior wall and ceiling finish class by occupancy group and location. Each row gives three locations, in this order: interior exit stairways (with ramps and exit passageways), then corridors, then rooms and enclosed spaces. Each location has a sprinklered value and a nonsprinklered value. Reading the columns in the wrong order is a common error.
Groups B, E, M and R-1
- Sprinklered: B in interior exit stairways, C in corridors, C in rooms
- Nonsprinklered: A in interior exit stairways, B in corridors, C in rooms
So a sprinklered Group B office needs Class B in its interior exit stairways. Class A is the nonsprinklered stairway value, and Class C is the sprinklered value for corridors and rooms, not exits. A nonsprinklered Group M store needs Class B in its corridors; Class A there belongs to the exit stairways and Class C to rooms. No restriction is the Group U entry and applies to nothing else.
Group I-3 does not relax in exits
The trap is assuming sprinklers give a blanket one-class reduction everywhere. They do not. A Group I-3 detention facility requires Class A in interior exit stairways even when sprinklered throughout with NFPA 13. Only its rooms and enclosed spaces drop to Class C. Class B in a sprinklered exit is the Group B, E, M and R-1 value, not I-3.
What counts as sprinklered
The sprinklered column applies only to a building protected per Section 903.3.1.1 or 903.3.1.2, meaning an NFPA 13 or NFPA 13R system. A partial system, such as sprinklers in storage rooms only, does not qualify. The nonsprinklered column then governs, so a Group B building with sprinklers only in its storage rooms still needs Class A in its interior exit stairways. Class B would apply only if the building were fully sprinklered. The table has no provision for splitting the requirement by sprinklered floor.