California Code of Regulations · Title 24
The California Building Standards Code, explained
The California Building Standards Code (Title 24) is organized into 13 parts — the building, residential, electrical, mechanical, plumbing, energy, fire, green and other codes that govern construction across the state. The 2025 edition is current, effective January 1, 2026.
Pick a part below for a plain-English overview — or ask GoCodebook a question and get the controlling section for your jurisdiction with a citation.
The 13 parts of Title 24
Part 1
California Administrative Code (CAC)
Administrative regulations and procedures that govern how the California Building Standards Code is adopted and enforced.
Learn morePart 2
California Building Code (CBC)
Structural, fire, accessibility and occupancy requirements for commercial and multifamily buildings.
Learn morePart 2.5
California Residential Code (CRC)
Construction standards for one- and two-family dwellings and townhouses up to three stories.
Learn morePart 3
California Electrical Code (CEC)
Electrical installation, wiring and safety requirements based on the National Electrical Code.
Learn morePart 4
California Mechanical Code (CMC)
HVAC, ventilation, exhaust and mechanical system requirements.
Learn morePart 5
California Plumbing Code (CPC)
Plumbing, drainage, venting and water-supply requirements.
Learn morePart 6
California Energy Code
Energy-efficiency standards for residential and nonresidential buildings (Title 24, Part 6).
Learn morePart 7
California Wildland-Urban Interface Code (CWUIC)
Fire-resistant construction requirements for buildings in wildfire-prone (WUI) areas.
Learn morePart 8
California Historical Building Code (CHBC)
Alternative standards that preserve qualified historic buildings while protecting safety.
Learn morePart 9
California Fire Code (CFC)
Fire prevention, protection systems and life-safety requirements.
Learn morePart 10
California Existing Building Code (CEBC)
Repair, alteration, addition and change-of-occupancy provisions for existing buildings.
Learn morePart 11
California Green Building Standards Code (CALGreen) (CALGreen)
Green building, water-efficiency and sustainability requirements.
Learn morePart 12
California Referenced Standards Code (CRSC)
The referenced standards adopted into and enforced under Title 24.
Learn moreWhat makes Title 24 its own thing
Title 24 isn't one book, and it isn't purely a California invention. Four things explain most of the confusion around it.
Model code plus California
Most parts adopt a national model code (the IBC, IRC, NEC, UPC and so on) and then amend it. In the printed codes those state amendments are set in italics — the base text is national, the italics are California.
Some parts are California's own
The Energy Code (Part 6) and CALGreen (Part 11) aren't amended model codes — the state wrote them. They have no national counterpart, and they're where California diverges most from the rest of the country.
A three-year cycle
A new edition is published every three years. The 2025 edition is effective January 1, 2026; which edition governs a given project generally follows the date the permit application was filed.
Cities can amend it
Local jurisdictions may adopt amendments that are more restrictive than the state code where they can justify it. So the state text is the starting point, not always the final requirement.
Which part covers what you're doing
A rough routing table. Most projects touch several parts at once — a kitchen remodel pulls in plumbing, electrical and energy — but this is where to start.
| If you're working on… | Start with |
|---|---|
| A house, duplex, or townhouse up to three stories | California Residential Code (CRC), Part 2.5 |
| Anything else — commercial, multifamily over three stories, mixed use | California Building Code (CBC), Part 2 |
| Accessibility and ADA-equivalent requirements | CBC Chapter 11A/11B, Part 2 |
| Insulation, glazing, HVAC efficiency, solar readiness | California Energy Code, Part 6 |
| Bathroom fixtures, water heaters, gas and drain lines | California Plumbing Code (CPC), Part 5 |
| Panels, circuits, EV charging, service capacity | California Electrical Code (CEC), Part 3 |
| Egress, sprinklers, alarms, occupancy loads | California Fire Code (CFC), Part 9 |
| Water and energy conservation on new construction | CALGreen, Part 11 |
| Additions and alterations to an existing building | California Existing Building Code, Part 10 |
| Building in a high fire-severity zone | Wildland-Urban Interface Code (CWUIC), Part 7 |
Common questions
Which edition of Title 24 applies to my project?
California publishes a new edition every three years; the 2025 edition took effect January 1, 2026. In general the edition in force when your permit application is filed governs the project, so work permitted before an effective date usually stays under the prior edition. Your building department confirms this for a specific permit.
What's the difference between the CBC and the CRC?
The California Residential Code (Part 2.5) covers detached one- and two-family dwellings and townhouses up to three stories. Everything else — commercial buildings, larger multifamily, mixed use — falls under the California Building Code (Part 2). Some projects can be designed under either, and that choice changes which requirements apply.
Why is some code text in italics?
In the parts that adopt a national model code, italics mark California's own amendments to that model text. It's a quick way to see where the state has departed from the national baseline. The state-authored parts, like the Energy Code and CALGreen, don't use that convention.
Can my city require something stricter than Title 24?
Yes. Local jurisdictions can adopt amendments more restrictive than the state code when they make the findings state law requires. That's why a project meeting the state minimum can still fail a local requirement — check the city's adopting ordinance alongside the state code.
Read the enacted text in the Code Library, or see more answered questions.