California Building Standards & Health and Safety Code: Title 24

California Title 24 building standards are the state’s enforceable technical rules for construction, covering structural safety, electrical and plumbing work, energy efficiency, fire protection, and green building. The current version is the 2025 edition, which took effect on January 1, 2026, and applies to permits pulled under its coverage statewide.¹ Whether you are building a new home, remodeling, or hiring a contractor for a smaller job, Title 24 determines what your plans must show, what inspectors will check, and when your project is legally finished.

What Title 24 Covers

Title 24 is not one document. It is a set of separate codes, each handling a different construction discipline, and each project touches only the parts that match its scope.²

California Building Code (Part 2) — structural design, occupancy classifications, and life safety for most building types.
California Residential Code (Part 2.5) — one- and two-family dwellings and townhouses, with simplified prescriptive rules.
California Electrical Code (Part 3) — wiring and electrical safety, based on the National Electrical Code with California amendments.
California Mechanical Code (Part 4) — heating, ventilation, air conditioning, and refrigeration.
California Plumbing Code (Part 5) — water supply, drainage, and waste.
California Energy Code (Part 6) — insulation, lighting, HVAC efficiency, and solar requirements.
California Historical Building Code (Part 8) — flexibility for preserving historic properties.
California Fire Code (Part 9) — emergency access, suppression systems, alarms, and wildfire provisions.
California Existing Building Code (Part 10) — alterations, additions, and repairs to existing structures.
CALGreen (Part 11) — water conservation, construction waste diversion, and sustainable building practices.

If you are remodeling, Part 10 will usually be your reference point. New single-family work pulls in Parts 2.5, 3, 4, 5, 6, 9, and 11 at minimum. Commercial projects run through Part 2 and often the full stack.

How the 2025 Edition Took Effect, and When It Changes Again

California updates Title 24 on a three-year cycle. The California Building Standards Commission reviews proposals from state agencies through public hearings and workshops before adopting a new edition.¹ Health and Safety Code Section 18938 then imposes a mandatory 180-day waiting period before a new edition is enforceable, giving designers, contractors, and local departments time to catch up. Amendments that make a standard less restrictive take effect 30 days after the Commission files them with the Secretary of State.³

Between full cycles, the Commission can publish intervening supplements to fix errors or respond to emerging hazards, using the same public comment process. The practical rule: your project is governed by the edition in force when you apply, so timing matters at the margins of a code cycle.

The Solar Requirement for New Homes

If you are building a new single-family residence, townhouse, or duplex, Section 150.1(c)14 of the 2025 Energy Code requires solar photovoltaic panels.⁴ The mandate first applied in 2020 and continues under the current edition.

There are several ways out. No system is required if the roof has less than 80 contiguous square feet of usable solar access after shading, if the calculated minimum system size would be less than 1.8 kilowatts, or if snow load requirements cannot be met. A qualifying battery energy storage system with at least 7.5 kilowatt-hours of cycling capacity lets you cut the required solar size by 25 percent.⁴ The mandate does not reach additions or alterations to existing buildings; if you are remodeling, it does not apply to you.

When Local Rules Add to Title 24

Cities and counties can go stricter than the statewide code, but only when they make formal written findings that local climatic, geological, or topographical conditions justify the change. Health and Safety Code Section 17958.5 sets that authority, and Section 17958.7 requires the jurisdiction to file both the findings and the amendment with the Building Standards Commission before the amendment is enforceable. The Commission can reject a filing that lacks the required findings.⁵⁶

A Temporary Freeze on Local Residential Amendments

From October 1, 2025 through June 1, 2031, cities and counties generally cannot adopt new local amendments affecting residential units. The legislature left narrow exceptions: amendments substantially equivalent to those already filed and in effect as of September 30, 2025; emergency standards the Commission deems necessary for health and safety; amendments related to home hardening; and certain administrative streamlining measures such as reducing permit processing times. The Commission must reject residential amendments that do not fit one of these.⁵⁶ If you are building a residential project through 2031, expect the statewide code to govern almost everything, with far fewer local add-ons than in past cycles.

Federal Rules That Sit on Top of Title 24

Some construction is subject to federal law in addition to, or instead of, Title 24.

Manufactured Housing Is Federal, Not State

Factory-built manufactured homes are governed by federal HUD standards under 42 U.S.C. Chapter 70, which expressly preempts state and local building codes: no state or local government may enforce a construction or safety standard for manufactured homes that differs from the federal standard. California retains authority over foundations and stabilizing systems for homes sited in the state, but those standards must be consistent with the manufacturer’s design.⁷ Federal installation standards under 24 CFR Part 3285 set the baseline for initial setup, and California operates its own installation program that must equal or exceed the federal model.⁸ If you are buying or siting a manufactured home, Title 24 is largely not your reference.

ADA Accessibility for Commercial and Public Buildings

The Americans with Disabilities Act requires commercial buildings and facilities open to the public to meet the 2010 ADA Standards for Accessible Design. These apply to new construction, renovations that affect usability, and, in some cases, existing buildings. Title II obligates state and local government facilities to provide program access; Title III requires private businesses to remove architectural barriers when doing so is readily achievable.⁹

Enforcement includes private civil lawsuits for injunctive relief and U.S. Attorney General actions where there is a pattern of discrimination. Federal regulations set civil penalties up to $75,000 for a first violation and $150,000 for subsequent violations, subject to inflation adjustments.¹⁰ California’s own accessibility rules in Title 24 often exceed ADA minimums, and your project must meet whichever standard is more protective.

Stormwater on Larger Sites

Any construction project that disturbs one acre or more of land must obtain a Construction General Permit through the National Pollutant Discharge Elimination System under the Clean Water Act. Smaller sites that are part of a larger development ultimately disturbing one or more acres are also covered.¹¹ Operators must develop a Stormwater Pollution Prevention Plan and file a Notice of Intent at least 14 calendar days before earth-disturbing work begins.¹²

What Compliance Looks Like: Documents, Permits, and Inspections

A permit application has to prove on paper that the project meets every applicable part of Title 24. At minimum you will prepare architectural plans with the correct occupancy type and construction classification, structural calculations from a licensed engineer, Title 24 energy compliance reports showing the design meets Energy Code requirements (including solar for new homes), and a site survey showing property lines, setbacks, utilities, and the proposed structure’s location.

The numbers on your application — square footage, occupancy classification, project valuation — have to match your drawings exactly. Mismatches are a common reason plan check sends an application back.

Once the plans pass review, the local department issues the building permit. Review timelines vary widely. A simple residential remodel might clear in a few weeks; a commercial project in a busy jurisdiction can take months. Construction then runs through a sequence of inspections timed so problems get caught before they are buried behind finished surfaces:

Foundation and underground plumbing, before concrete.
Structural framing, before insulation or drywall.
Rough-in mechanical, electrical, and plumbing, while still exposed.
Insulation and energy, before walls are closed.
Final inspection, confirming everything works and the building is safe for occupancy.

Passing the final inspection produces a certificate of occupancy, the document that legally authorizes anyone to live or work in the building.

Permits Expire if You Sit on Them

Under Health and Safety Code Section 18938.6, a building permit stays valid as long as work begins within 12 months of issuance.¹³ Let a year pass without starting, and you may have to reapply under whatever code edition is current then. For long projects, steady visible progress is what keeps the permit alive.

Challenging a Building Official’s Decision

If a building official reads the code in a way you believe is wrong, you can appeal to the local appeals board — the board or agency the city or county has authorized to hear building disputes. Section 113 of the California Building Code allows appeals on three grounds: that the code was interpreted incorrectly, that its provisions do not fully apply to the situation, or that an equally good or better construction method is proposed. The board cannot waive code requirements, only decide how they are applied. Where no appeals board exists, the city or county governing body itself serves in that role.

Insurance for Code-Upgrade Costs

After a covered loss, the building department will require you to rebuild to the current Title 24 edition. If the original structure predates modern energy, seismic, or fire safety rules, the upgrade cost can be significant, and many homeowners find out too late that their policy does not automatically pay for it.

California Insurance Code Section 10103 requires residential property policies with replacement cost coverage to include at least 10 percent of the dwelling coverage limit as additional building code upgrade coverage, and that amount cannot deplete the main dwelling coverage. Policies that lack this coverage have to display a prominent notice on the declarations page saying so. Where coverage is included, the insurer must disclose the limits and any restrictions on a separate form attached to the declarations page. Check your policy before you ever need it, and ask whether 10 percent is enough to fund a true code-compliant rebuild of your particular home.

Hiring a Contractor Who Can Legally Do the Work

Most construction in California requires a licensed contractor. As of January 1, 2025, an unlicensed person may only perform work where the total price for labor and materials is under $1,000, no building permits are needed, and no workers are hired.¹⁴ Anything above that threshold, or any project that pulls a permit or uses employees, requires a license in the appropriate classification.

Penalties for unlicensed contracting include administrative fines up to $15,000, jail time up to six months, and criminal fines up to $5,000. Repeat offenders face a mandatory 90-day jail sentence and a fine of $5,000 or 20 percent of the contract price, whichever is greater.¹⁴ Contracts performed by unlicensed contractors are generally unenforceable, so the contractor may not be able to collect on completed work — and your project’s legal standing in any later dispute depends on who did the job.

1
California Department of General Services. 2024 Triennial Code Adoption Cycle
2
California Department of General Services. Codes
3
California Legislative Information. California Health and Safety Code 18938
4
California Energy Commission. 2025 Single-Family Solar PV
5
California Legislative Information. California Health and Safety Code 17958.5
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California Legislative Information. California Health and Safety Code 17958.7
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Office of the Law Revision Counsel. 42 USC 5403 – Construction and Safety Standards
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eCFR. Model Manufactured Home Installation Standards
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ADA.gov. ADA Design Standards
10
ADA.gov. Title III Regulations
11
U.S. Environmental Protection Agency. Stormwater Discharges from Construction Activities
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U.S. Environmental Protection Agency. Construction General Permit Frequent Questions
13
California Department of General Services. Part 2 Chapter 1 Scope and Administration
14
Contractors State License Board. Handyperson Exemption to Increase to $1,000 in 2025