Title 24 California Code of Regulations: Parts and Compliance

Title 24 of the California Code of Regulations, known formally as the California Building Standards Code, is the single set of construction rules that governs every building project in the state. It’s organized into 12 parts covering structural safety, fire protection, energy efficiency, accessibility, plumbing, electrical, mechanical, and green building. If you’re constructing a new home, adding a room, replacing an HVAC system, or building a commercial project, your work has to meet Title 24’s minimum standards. The 2025 edition took effect on January 1, 2026, and applies to any permit application filed on or after that date.¹

The 12 Parts of Title 24

Each part of Title 24 adopts a national model code and then amends it to fit California conditions like seismic activity, wildfire risk, and the state’s energy-reduction goals.²

Part 1 — California Administrative Code, the procedural rules for how the other parts are applied
Part 2 — California Building Code (structural integrity, fire safety, occupancy classifications)
Part 2.5 — California Residential Code, for one- and two-family dwellings and townhouses
Part 3 — California Electrical Code
Part 4 — California Mechanical Code
Part 5 — California Plumbing Code
Part 6 — California Energy Code
Part 7 — California Wildland-Urban Interface Code, a new standalone code created in the 2025 cycle³
Part 8 — California Historical Building Code
Part 9 — California Fire Code
Part 10 — California Existing Building Code
Part 11 — California Green Building Standards Code (CALGreen)
Part 12 — California Referenced Standards Code

Three kinds of standards end up in these parts: provisions adopted directly from national model codes, provisions California has modified, and provisions the state legislature created from scratch.² The parts that generate the most questions for homeowners and developers are the Energy Code, CALGreen, and the accessibility chapters in Part 2.

Energy Efficiency Under Part 6

The California Energy Code is overseen by the California Energy Commission and sets the energy performance floor for essentially every new building, addition, and major alteration.⁴ The 2025 edition expands heat pump requirements for new residential construction and continues pushing California toward all-electric buildings.¹

There are two ways to comply. The prescriptive path is a checklist: insulation must meet a specified R-value, windows must meet a specified U-factor, and so on. Every component has to hit its number. The performance path is more flexible. You run an energy model of the whole building using CEC-approved software, and the model calculates whether total energy use stays below an allowed budget. A less-insulated wall can be offset by a higher-efficiency HVAC system. Most custom homes and commercial projects use the performance path because it leaves more room for design tradeoffs.

Before you can pull a permit, energy compliance forms have to be submitted to the local building department. Residential projects use three: the Certificate of Compliance (CF1R) documents the design and is signed by a licensed architect, engineer, or (where a licensed designer isn’t required) the builder; the Certificate of Installation (CF2R) is signed by the subcontractor who installs each system; and the Certificate of Verification (CF3R) is signed by an energy consultant rater who field-tests the installed work. All three have to be registered and signed before you get final inspection approval.⁵

When a Remodel or Addition Triggers Title 24

Title 24 isn’t only for new construction, and that surprises a lot of homeowners. If you change the building envelope, replace a heating or cooling system, or add conditioned living space, energy compliance documents are required.

For additions, the requirements scale with size. An addition of 400 square feet or less has relaxed glazing limits and is exempt from quality insulation installation verification. Between 400 and 700 square feet, glazing rules tighten. Over 700 square feet triggers the full prescriptive requirements, including quality insulation installation verification for the added area.⁶

Alterations that add no square footage can still trigger compliance. Replacing an air handler, outdoor condensing unit, or heating coil counts as an alteration and brings duct-sealing requirements with it. Replacing 50 percent or more of your roof surface in certain climate zones triggers cool-roof requirements. Replacing lighting can require the new fixtures to meet current standards, though fixtures you don’t touch can stay. Simple maintenance repairs that don’t increase a component’s energy consumption are generally exempt.⁶

CALGreen Requirements Under Part 11

CALGreen is California’s mandatory green building code. It goes beyond energy to cover water efficiency, construction waste, and electric vehicle infrastructure, and it applies to every new residential and commercial building.

For single-family homes with attached garages, CALGreen requires a dedicated raceway from the electrical panel to the garage, sized to support a 40-amp, 240-volt EV charger circuit. For multifamily buildings, the 2025 code raised the share of common parking spaces that must have Level 2 EV chargers from 10 percent to 25 percent. Bicycle parking in new multifamily buildings, hotels, and motels also became mandatory in the 2025 cycle after previously being voluntary.³

CALGreen also requires construction waste diversion, low-water-use plumbing fixtures, and moisture-control measures. These mandatory provisions are a floor. Many local jurisdictions have adopted stricter reach codes on top of them.

Accessibility: Chapters 11A and 11B

California’s accessibility rules live in Part 2 of the Building Code, split across two chapters. Chapter 11A covers housing accessibility for privately funded multifamily residential projects and generally tracks the federal Fair Housing Act. Chapter 11B covers accessibility in public buildings, commercial spaces, and publicly funded housing, and it ties to the Americans with Disabilities Act.⁷

Chapter 11B is where California goes further than federal minimums, requiring a higher degree of accessibility for elements like the path of travel, parking, restrooms, and signage than the ADA alone demands. The Division of the State Architect develops and enforces these standards, and DSA review is mandatory for state-funded buildings, public schools, and community colleges.⁷ Private commercial projects also have to meet Chapter 11B, though enforcement usually runs through the local building department.

One notable 2025 change: newly constructed multifamily dwellings that qualify as public housing were removed from Chapter 11A’s scope and now fall entirely under Chapter 11B’s stricter requirements.⁸

How Compliance Actually Happens

Local city and county building departments administer and enforce Title 24. The sequence is design, plan check, permit, inspections, final sign-off.

You submit construction documents for plan check review. A typical residential submission includes signed architectural drawings, structural calculations, the CF1R energy compliance form, signed CALGreen documentation, and, if the property sits in a wildland-urban interface zone, high-wind area, or flood zone, that flagged on the plans. The department verifies the documents meet all applicable code requirements before issuing a permit.

Construction then becomes subject to mandatory inspections at key stages, typically foundation, framing, mechanical and electrical rough-in, insulation, and final. At each stage the inspector confirms the work matches the approved plans. After a passing final inspection, the department issues a Certificate of Occupancy for a new building, or a Certificate of Completion for an alteration. Without that certificate, occupying the building is a code violation.

Penalties for Non-Compliance

Violations carry real consequences. When an inspector finds work that doesn’t match approved plans or discovers unpermitted construction, the department can issue a stop-work order that halts all activity immediately. Nothing moves until the violation is resolved, which usually means revised plans and additional fees.

Under California Health and Safety Code Section 18874, willfully violating the building standards code is a misdemeanor. Criminal penalties include a fine of up to $400, up to 30 days in county jail, or both. Each violation also carries a civil penalty of $500 per day for as long as it continues.⁹ On a project with multiple violations that persist for weeks, the daily penalties add up quickly.

Licensed contractors face additional discipline from the Contractors State License Board. Failing to obtain a required building permit is itself a violation, and the CSLB can assess civil penalties of up to $5,000 per violation on top of requiring payment of all permit fees and local penalties. Repeated violations can lead to license suspension or revocation.¹⁰

Local Reach Codes Can Go Further

Title 24 sets the floor. Cities and counties are allowed to adopt stricter standards when local conditions justify it. Under Health and Safety Code Section 18941.5, a local government can enact more restrictive standards, including green building standards, if it makes findings that the stricter requirements are reasonably necessary because of local climate, geology, or topography.¹¹

Dozens of California cities have used this authority to adopt reach codes that go beyond the state energy code or CALGreen. Some require all-electric new construction. Others mandate higher levels of solar coverage. If you’re building anywhere in California, checking the local jurisdiction’s amendments matters as much as knowing the state code, because the local ordinance is what actually gets enforced at the permit counter. A local amendment takes effect only for permit applications filed after its effective date.¹²

What Changed in the 2025 Edition

Title 24 updates on a mandatory three-year cycle. State agencies review the latest editions of national model codes, propose California-specific amendments, and the California Building Standards Commission coordinates the process across all contributing agencies. Each new edition publishes mid-year and takes effect the following January 1.³ The edition that applies to your project depends on when your permit application is filed, not when construction starts or finishes.¹

The 2025 edition, published July 1, 2025 and effective January 1, 2026, brought several significant changes beyond the EV charging and accessibility updates above:²

A new Wildland-Urban Interface Code (Part 7) that consolidates fire-hardening requirements previously scattered across the Building Code, Residential Code, and Fire Code into a single standalone code.³
New hospital resilience requirements. Acute care hospitals must have on-site power sources capable of supporting 72 hours of full-demand operation, and emergency water supply and sanitary drainage systems must also support 72 hours of continuous operation.³
CO₂ monitoring in classrooms. New construction for University of California, California State University, and private school classrooms must include carbon dioxide monitoring systems.³
Seismic deadline flexibility. Small, rural, and critical-access hospitals can now seek a delay of up to three years on the January 1, 2030 seismic safety compliance deadline.³

The creation of Part 7 as a standalone wildfire code is probably the most consequential structural change in the 2025 cycle. Pulling fire-hardening, defensible space, water supply, and accessibility requirements for buildings near wildland areas into one code makes compliance easier to navigate than hunting through three separate parts.

1
California Energy Commission. 2025 Building Energy Efficiency Standards
2
Department of General Services. Codes
3
California Department of General Services. 2025 Title 24 California Code Changes
4
California Energy Commission. Building Energy Efficiency Standards
5
California Energy Commission. 2025 Single-Family Residential Compliance Manual
6
California Energy Commission. Chapter 9 – Additions, Alterations, and Repairs
7
Department of General Services Building Standards Commission. 2025 Part 2 Chapter 11B Accessibility to Public Buildings
8
Department of General Services Building Standards Commission. 2025 Part 2 Chapter 11A Housing Accessibility
9
California Legislative Information. California Health and Safety Code Part 2.3 Chapter 11
10
CSLB – CA.gov. Filing a Building Permit Violation Form
11
Department of General Services. Local Amendments to Building Standards – Ordinances
12
California Legislative Information. California Health and Safety Code 18938.5