California ADU Laws (2026): The Complete, Cited Guide

California's ADU law is among the most homeowner-friendly in the country. It's also scattered across dozens of bills passed since 2016. This page pulls the key rules together, with citations to the Government Code and to the California Department of Housing and Community Development's (HCD) official ADU Handbook, updated March 2026.

Please read this first: this is general information, not legal advice. Local ordinances can be more permissive than state law, and sometimes impose objective standards within state limits. Confirm details with your city or county, and with the statute itself at leginfo.legislature.ca.gov. Where we weren't able to confirm a detail against an official source, we say so.

Where the law lives now: Gov. Code 66310–66342

In March 2024, SB 477 recodified State ADU Law. The old sections (65852.2, 65852.22 and others) were repealed and moved into a new Chapter 13 of Division 1 of Title 7 of the Government Code, sections 66310–66342, effective March 25, 2024. SB 477 was intended as a non-substantive reorganization. HCD's 2026 Handbook notes that 2025 legislation renumbered some sections again. For example, the fee rules formerly at 66324 are now at 66311.5.

The structure:

• Article 1 (66310–66313.5): findings, definitions, fees
• Article 2 (66314–66332): ADUs, including standards, approvals, the 66323 "exempt" units and unpermitted ADUs
• Article 3 (66333–66339.5): JADUs
• Article 4 (66340–66342): sales and separate conveyance

How big can an ADU be?

• Local maximum-size rules must allow at least 850 sq ft, or 1,000 sq ft for more than one bedroom (Gov. Code section 66321(b)(2)).
• Without a compliant local ordinance, the default maximum is 1,200 sq ft for a new detached ADU, and up to 50% of the primary home's floor area for an attached ADU (section 66314(d)(4)–(5)).
• Lot coverage, floor-area ratio and open-space rules can't block an ADU of at least 800 sq ft with 4-foot side and rear setbacks (section 66321(b)(3)).
• Conversions of existing space aren't subject to unit-size limits (section 66323(a)(1)).
• Minimum size can't prohibit an efficiency unit, which can be as small as 150 sq ft (Health & Safety Code section 17958.1).

How many units per lot?

On a single-family lot, HCD's Handbook describes combinations that allow:

• one ADU (converted, attached or detached), plus
• one JADU, plus
• in many cases, an additional detached new-construction ADU of up to 800 sq ft (a "66323 unit")

On multifamily lots:

• ADUs within non-livable space (storage, garages, basements), with at least one and up to 25% of the existing units.
• SB 1211 (effective Jan. 1, 2025) lets lots with an existing multifamily building add up to eight detached ADUs, as long as that number doesn't exceed the number of existing units. A lot with a *proposed* multifamily building is limited to two detached ADUs (section 66323(a)(4)). SB 1211 also defined "livable space," which opens rooms like laundry rooms to conversion.

Setbacks

• Side and rear setbacks for new ADUs can't exceed 4 feet (see sections 66314 and 66321(b)(3)).
• No setback may be required for an ADU in an existing legal structure, or one rebuilt in the same location with the same dimensions.
• Front setbacks: local rules apply, but they can't preclude an 800 sq ft ADU (section 66321(b)(3)). Ask your city.

Height limits

Cities can't set limits below these (section 66321(b)(4)):

• 16 feet for a detached ADU
• 18 feet for a detached ADU within a half-mile walk of a major transit stop or high-quality transit corridor, plus 2 feet to match the roof pitch of the main home
• 18 feet for a detached ADU on a lot with a multistory multifamily building
• 25 feet, or the primary-home limit if lower, for an attached ADU

HCD says a city can't deny a two-story ADU that fits these allowances and the building code. See two-story ADUs.

Parking

• No more than one space per unit or bedroom, whichever is less, and tandem driveway parking must be allowed (section 66314(d)(10)).
• No parking may be required if the ADU (section 66322(a)):
  • is within a half-mile walk of public transit
  • is in an architecturally and historically significant district
  • is part of the existing home or an accessory structure
  • is somewhere on-street permits are required but not offered to the ADU occupant
  • is within one block of a car-share vehicle
  • is applied for together with a new home on the same lot (if other criteria are met)
• No replacement parking when a garage, carport, covered space or, since SB 1211, an uncovered space is demolished or converted for an ADU (section 66314(d)(11)).
• JADUs never require parking.

Owner occupancy

• ADUs: cities can't impose owner-occupancy requirements (section 66315). The narrow exception is ADUs sold under section 66341.
• JADUs: as of Jan. 1, 2026 (AB 1154), owner occupancy may be required only if the JADU shares sanitation facilities with the main home. The owner may live in either part. No owner occupancy is required if the JADU has its own bathroom (section 66333(b)).

The approval clock

• Ministerial review only, with no hearings or discretionary design review.
• 60 days to approve or deny a complete application. If the agency misses it, the application is deemed approved (section 66317).
• New for 2026: a written completeness determination within 15 business days, a list of missing items if the application is incomplete, and an appeal process with a final written decision within 60 business days (section 66317, per HCD's 2026 addendum).
• Coastal zone: the coastal development permit must be approved or denied within 60 days of a complete application.
• Denials must include a full set of comments explaining how to fix the deficiencies.
• Cities can't deny an ADU to force correction of unrelated nonconforming zoning or code conditions that don't threaten health and safety (section 66322(b)).

Fees

Per section 66311.5:

• No impact fees on ADUs of 750 sq ft or less (this came from SB 13, 2019), or on JADUs of 500 sq ft or less.
• Above those sizes, impact fees must be proportional to the square footage of the primary home.
• Generally no separate connection or capacity charges for ADUs within existing space, or for JADUs. For other ADUs, charges must be proportional.
• School fees generally apply only to units over 500 sq ft.

JADU rules

Per section 66333:

• No more than 500 sq ft, entirely within the walls of a single-family home. An attached garage counts.
• A separate entrance, and an efficiency kitchen with a cooking appliance, prep counter and storage.
• A shared or separate bathroom. With a shared bathroom, an interior connection is required and owner occupancy may be required.
• A recorded deed restriction barring separate sale.
• Rentals must be for longer than 30 days.

HOAs

Civil Code sections 714.3 and 4751 void CC&Rs that prohibit or unreasonably restrict ADUs and JADUs on single-family lots. HOAs may impose only reasonable objective standards.

Pre-approved plans (AB 1332)

By Jan. 1, 2025, every local agency had to create a program for pre-approving ADU plans. It must accept submissions from any party and post approved plans online. See our pre-approved ADU plans page.

Unpermitted ADUs (AB 2533)

Since Jan. 1, 2025, cities can deny a permit to legalize an ADU or JADU built before Jan. 1, 2020 only if fixing the violation is necessary to meet the substandard-building criteria in Health & Safety Code section 17920.3. Penalties and most fees are barred (section 66332). See our guide.

Selling ADUs separately (AB 1033)

Section 66342 lets a city or county opt in to allow ADUs to be sold as condominiums. Conditions include:

• Davis-Stirling compliance
• Subdivision Map Act compliance
• a safety inspection
• lienholder consent
• utility notices
• HOA approval where one exists

San Diego County's ordinance for unincorporated areas took effect April 4, 2026. See our AB 1033 guide.

SB 9 (2021): duplexes and lot splits

SB 9 of 2021 (Gov. Code sections 65852.21 and 66411.7) allows two units and/or an urban lot split on most single-family lots. It's separate from ADU law, and lot splits require a three-year owner-occupancy affidavit. Cities may cap units on split lots, including ADUs. See SB 9 vs ADU.

SB 9 (2025): local ordinances

A different bill with the same number, SB 9 of 2025, provides that a local ADU ordinance is null and void if it isn't submitted to HCD within 60 days of adoption, or if the agency doesn't respond to HCD's findings within 30 days. Section 66333.5 applies the same rule to JADU ordinances. When an ordinance is void, only State ADU Law applies.

Other 2025 changes noted by HCD

HCD's Handbook lists 2025 legislation including AB 1154, SB 9, SB 543, AB 462 and AB 130. Changes include the completeness and appeal timelines, coastal-zone processing, and fee clarifications. We've summarized the provisions we confirmed against HCD's addendum. For anything else, read the Handbook addendum directly.

Older milestones, for context

• AB 68 and AB 881 (2019): set up the modern framework, including 4-foot setbacks, the 60-day clock (then shortened from 120 days), multifamily ADUs, and limits on lot-size and owner-occupancy rules.
• SB 13 (2019): removed impact fees for ADUs of 750 sq ft or less, and paused owner occupancy. AB 976 (2023) made the owner-occupancy ban permanent.
• AB 2221 and SB 897 (2022): added the height allowances, front-setback limits and the nonconforming-condition protections.

When a city gets it wrong

Contact HCD's Housing Accountability Unit through the HCD ADU page. HCD can notify the Attorney General when a local agency violates State ADU Law.

Frequently asked questions

This page is general information, not legal, tax or financial advice. Costs vary by property and builder. Images are AI-generated illustrations. Last updated November 2026.