CodeMandatory
Flame-spread index of interior finishes
IRC R302.9Description
Wall and ceiling interior finishes must have a flame-spread index ≤200 and a smoke-developed index ≤450.
Why this exists
Some decorative finishes accelerate fire spread; minimum performance ratings cap the worst options.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
maxFlameSpread | max | 200 | index | |
maxSmokeDeveloped | max | 450 | index |
Categories
Life safety
Source
ICCno manifest entry
International Residential Code (2024)
Section: R302.9
Published 2024-01-01 · last verified 2026-05-09
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Garage / dwelling fire separation · IRC R302.6
- Habitable space minimum ceiling height · IRC R305.1
- Egress window net opening dimensions · IRC R310.2
- Stair riser, tread, and headroom · IRC R311.7
- Smoke alarms required throughout dwelling · IRC R314
Last reviewed 2026-05-09.