In California's CRC, R310 Is Smoke Alarms — Not Egress Windows
IRC-trained checkers expect R310 to be the egress window. In California's 2025 code it's smoke alarms — here's the real Chapter 3 map.
Open the model International Residential Code to Chapter 3 and the muscle memory is automatic: R310 is emergency escape and rescue openings, R311 is means of egress, R312 is guards and window fall protection. Anyone who learned residential numbering from the IRC knows that trio cold.
Here's the thing: none of it holds in California.
The 2025 California Residential Code — Title 24, Part 2.5, effective January 1, 2026 — numbers the front half of Chapter 3 differently from the model IRC. California slotted its own sections in early, and everything after them sits lower than it does in the IRC. So the exact numbers you reach for point at completely different rules.
The same three numbers, three different subjects
In the CRC, R310 through R312 have nothing to do with egress:
- R310 is Smoke Alarms.
- R311 is Carbon Monoxide Alarms.
- R312 is Minimum Room Areas.
Verified against the 2025 California Residential Code, Chapter 3: the section headers read "SECTION R310—SMOKE ALARMS," "SECTION R311—CARBON MONOXIDE ALARMS," and "SECTION R312—MINIMUM ROOM AREAS."
Cite "R310" on a bedroom that's missing an egress window and you've written a smoke-alarm correction by accident. In the IRC that citation is right. In California it's a different part of the same book.
Where the egress rules actually live
The topics didn't disappear — they moved:
- Emergency escape and rescue openings — the egress window — is R319, not R310.
- Means of egress, including the required egress door and interior stairways, is R318, not R311.
- Guards and window fall protection is R321, not R312.
Verified against the 2025 CRC: Section R319 carries a California ([CA]) amendment requiring an operable emergency escape and rescue opening in "every sleeping room," and stairways are covered at Section R318.7.
Notice the pattern on stairways. In the IRC, stairways sit at R311.7, under Means of Egress. California keeps stairways as subsection ".7" under Means of Egress — it just renumbered the parent from R311 to R318. So the CRC's stairway section is R318.7. The internal logic tracks; the leading number doesn't.
The California Chapter 3 map, ready to bookmark
Here's the stretch that trips people up, straight from the section headers:
| Section | California CRC (2025) |
|---|---|
| R308 | Site Address |
| R309 | Automatic Sprinkler Systems |
| R310 | Smoke Alarms |
| R311 | Carbon Monoxide Alarms |
| R312 | Minimum Room Areas |
| R313 | Ceiling Height |
| R317 | Garages and Carports |
| R318 | Means of Egress (stairways at R318.7) |
| R319 | Emergency Escape and Rescue Openings |
| R320 | Handrails |
| R321 | Guards and Window Fall Protection |
The offset isn't even uniform, which is the real trap — you can't add a fixed number to the IRC citation and land in the right place. The emergency-escape section moved from IRC R310 down to CRC R319, a nine-section slide; guards moved from IRC R312 to CRC R321; means of egress went from IRC R311 to CRC R318. You have to look each one up.
Why this bites in the redline
A correction notice is only as good as its citation. Quote the wrong section and three things follow: the applicant's designer can't find the rule you mean, a sharp permit expediter can push back that your cited section says something else entirely, and the correction is weaker if it's ever challenged. On a code-accuracy basis, "R310" for an egress window in California is simply the wrong section.
This is also why edition matters. Which code governs turns on timing — which Title 24 edition applies is set by your permit application date. And before you assume a section even applies to your project and agency, the matrix adoption table at the head of each chapter tells you who adopted it. If your title block still carries model-IRC numbers, you're not alone — and renumbering isn't unique to Chapter 3; other parts of Title 24 saw sections move in the January 2026 cycle.
Always confirm against your local jurisdiction's adopted edition and any local amendments before you finalize a correction — cities can and do amend Title 24. This isn't legal advice; it's a nudge to cite the section that actually says what you mean.
What CrossBeam does with it
CrossBeam reads plans against the California code that actually applies, so corrections point at the real section — R319 for the egress window, not R310. It flags wrong-section and renumbered citations before they land in a redline, so your notices hold up the first time.