CodeMandatory
Mezzanine area limits
IRC R325Description
Mezzanines must be ≤1/3 of the room area below, with ≥7 ft headroom both above and below the mezzanine floor.
Why this exists
Larger or shorter mezzanines reduce egress and habitable space ratios; the 1/3 rule keeps them as accessory space.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
maxAreaRatio | max | 0.333 | ratio | |
minHeadroom | min | 7 | ft |
Categories
Life safetyStructure
Source
ICCno manifest entry
International Residential Code (2024)
Section: R325
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.