CALIFORNIA • STATE-LEVEL RESEARCH
California ADU Laws: Find the Rule Behind Your Planning Decision
Start with the statewide guidance, then check the agency and property conditions that apply to your project. This hub connects the existing permit and JADU guides with official sources and practical worksheets.
2026 PLANNING YEAR
What changed in California ADU law for 2026?
California HCD’s March 2026 ADU Handbook incorporates several recent laws. The dates matter: some took effect January 1, 2026, while others became effective in 2025 but now shape 2026 projects.
| Law | Effective | What changed | What a homeowner should check |
|---|---|---|---|
| SB 543 | Jan. 1, 2026 | Adds a 15-business-day completeness determination, strengthens appeal procedures, and bases key size and fee thresholds on interior livable space. | Record the date your application was received, keep any completeness notice, and confirm how the agency measures interior livable space. |
| AB 1154 | Jan. 1, 2026 | For JADUs, owner occupancy is required when sanitation facilities are shared with the primary structure; it is not required when sanitation is separate. JADU rentals must be longer than 30 days. | Confirm whether the JADU will share sanitation and whether your intended rental arrangement complies. |
| SB 9 (2025) | Jan. 1, 2026 | Clarifies HCD oversight of local ADU ordinances: certain failures to submit or respond to HCD can make a local ordinance null and void, leaving State ADU Law to govern. | If a local rule conflicts with state law, ask the agency for the current ordinance and check HCD’s ordinance-review materials. |
| AB 462 | Oct. 10, 2025 | Clarifies coastal-zone processing, including 60-day action on a completed coastal development permit application in specified circumstances and concurrent processing with the ADU application. Coastal Act protections still apply. | Do not assume a coastal ADU is exempt from coastal review; identify the certified Local Coastal Program and the responsible reviewing agency. |
Primary reference: California HCD ADU Handbook, updated March 2026. This table is a homeowner planning summary, not a substitute for the current statute or parcel-specific local review.
California ADU planning guides by decision
Application and permit review
Understand submission, completeness review, corrections and the distinction between a legal deadline and a project schedule.
Comparing JADU vs. ADU Design Constraints
Compare the project types and the requirements to investigate before choosing a configuration.
Find Your California City or County Planning Authority
Build a jurisdiction file and use the available Los Angeles and San Diego starting points. A county name is not a substitute for identifying the responsible city or county agency.
Record the evidence
Track application requirements, agency notices, corrections and approvals in the permit worksheet.
Compare pre-approved ADU plans
See verified California city programs, plan options and the site-specific review that still applies.
What are California’s ADU application-review deadlines?
Completeness review and the permit decision are separate steps. Neither is a construction-completion promise.
- 15 business days — completeness. The permitting agency must send a written determination after receiving an ADU application. An incomplete notice must identify missing items and how to remedy them. A corrected resubmission receives the same review period; the agency cannot introduce new completeness items. Missing the determination deadline means deemed completeness for this section.
- 60 days — approve or deny. With an existing single-family or multifamily dwelling on the lot, the decision is due within 60 days after receipt of a completed application. This is not 60 business days. Denial must include written deficiencies and remedies within that period.
- Exceptions and missed deadlines. An accompanying application for a new primary dwelling can delay the ADU decision. An applicant-requested delay pauses the clock. The statute provides deemed approval when the applicable decision deadline is missed; obtain written confirmation and resolve permit requirements before starting work.
Source: Government Code §66317(a)–(b), amended by SB 543, effective January 1, 2026. Read the detailed California permit-process guide.
How should you check a legal claim?
- Find the current source. Start with the California HCD ADU Handbook, then locate the cited provision in California Legislative Information.
- Check the version and scope. Record the effective date, project type and exceptions. A proposed bill is not the same as an operative requirement.
- Check the local materials. Record the permitting agency, adopted ordinance, application checklist and fee schedule.
- Resolve uncertainty before committing. Ask the responsible agency for the applicable citation or written clarification. Keep that response with your project records.
Older code references need care: HCD notes that California ADU and JADU Government Code sections were renumbered in March 2024. Do not assume an older article cites the current section. See HCD’s notice and resources.
Old-to-current code reference table
This is a topic-level crosswalk, not a claim that whole sections were replaced one-for-one. SB 477 reorganized the law in March 2024; SB 543 made further moves effective January 1, 2026.
| Older citation | Where to look now | Topic |
|---|---|---|
| §65852.2 (multiple subdivisions) | Distributed across Chapter 13; use the specific topic below | Not a single replacement section |
| §65852.2(a)(3), (a)(7) | §66317 | ADU application review |
| §65852.2(c) | §66321 | Size and development-standard limits |
| §65852.2(f) → §66324 in 2024 | §66311.5, effective 2026 | Fees and utility charges |
| §65852.22 | §§66333–66339 for the 2024 JADU crosswalk; definitions also in §66313 | JADU requirements; current Article 3 extends through §66339.5 |
| §65852.23 → §66332 in 2024 | §66311.7, effective 2026 | Previously unpermitted ADUs and JADUs |
Sources: HCD’s 2024 statutory conversion table, final page; current statutes linked above; current JADU article. Sections 66340–66342 concern ADU sales, not the JADU rules. Read the current text: renumbering does not mean the wording stayed unchanged.
Can a pre-2020 unpermitted ADU be legalized?
AB 2533 expanded the permitting protections for unpermitted ADUs and JADUs built before January 1, 2020. The operative provision is now Government Code §66311.7, formerly §66332.
The provision limits denial based on the listed building-standard and ADU-rule violations. It is not blanket amnesty: an agency may find correction necessary under Health and Safety Code §17920.3, and buildings deemed substandard under that section are excluded. Before applying, homeowners may obtain a confidential third-party code inspection from a licensed contractor. Ask the local agency for its substandard-condition checklist and what documentation it needs.
Sources: AB 2533 and current §66311.7(a)–(d). Use our AB 2533 legalization guide and printable evidence checklist to screen a pre-2020 unit before applying.
What if the property is in the coastal zone?
Do not assume an ADU is exempt from coastal permitting. Use the current HCD handbook and ask the responsible agency which process applies. Our dedicated coastal-permitting guide is not yet published.
Does the 750-square-foot impact-fee exemption apply?
California Government Code § 66311.5(c)(1) prohibits the covered local-agency, special-district and water-corporation impact fees for an ADU with no more than 750 square feet of interior livable space. For larger ADUs, covered impact fees must be proportional to the primary dwelling’s square footage. Read § 66311.5(c).
This is not a waiver of every project fee. Subdivision (c)(2) excludes connection fees and capacity charges from its impact-fee definition. School fees have separate provisions; do not apply the 750-square-foot threshold to them. Ask each agency for an itemized fee estimate and its legal basis before entering an amount in your budget.
Fee summary checked against § 66311.5 on September 2, 2026. This section is guidance, not a fee calculator or a project-specific determination.
Continue your planning
Local rules and planning research · Arroyo Grande ADU Planning & Permit Guide · Yuba City ADU Planning & Permit Guide for Permit Planner and jurisdiction checks · Morro Bay ADU Coastal Planning & Permit Guide · Chico ADU Guide for pre-approved designs and City-supported site-plan preparation · Tools and worksheets · Budget, financing, contractor and construction guides
Directory and linked official starting points checked September 2, 2026. This is not a fresh legal audit of every linked guide. Each guide’s scope, sources and review status must be considered separately. Editorial standards.