California ADU Law: SB 1211 and Government Code 65852.2

California ADU law overrides local zoning to guarantee homeowners the right to build accessory dwelling units that meet objective state standards. The rules were originally codified at Government Code Section 65852.2, but Senate Bill 477 reorganized them in 2024. Standard ADUs now live at Government Code Sections 66310 through 66332, and Junior ADUs at Sections 66333 through 66340.¹ Senate Bill 1211, effective January 1, 2025, expanded what’s allowed on multifamily lots and killed replacement parking mandates. Local ordinances that still cite “65852.2” refer to the same substance under the old numbering.

How Many ADUs You Can Build

Single-Family Lots

On a lot with an existing or proposed single-family home, the local agency must allow at least one standard ADU (attached or detached) plus one Junior ADU built within the walls of the primary house. A Junior ADU is capped at 500 square feet of interior living space and must sit entirely inside the existing residence.² So a typical single-family owner can add two units: a full ADU in the backyard and a Junior ADU carved from existing square footage inside the house.

Multifamily Lots

Multifamily properties gained the most under SB 1211. The law creates two independent categories, and owners can use both at once.

Interior conversions: the local agency must allow at least one ADU created from non-livable space within an existing multifamily building, and up to 25 percent of the building’s existing unit count. Non-livable space includes storage rooms, boiler rooms, attics, and basements.³
Detached new construction: on a lot with an existing multifamily building, up to eight detached ADUs are permitted, though the number cannot exceed the total number of existing units on the lot. Lots with a proposed (not yet built) multifamily dwelling are capped at two detached ADUs.²

Before SB 1211, multifamily lots were capped at two detached ADUs regardless of property size.⁴ Under the new formula, a 20-unit apartment complex could add up to five interior conversions (25 percent of 20) plus up to eight detached ADUs on the same site, if the lot physically fits them. The two categories are separate; using one doesn’t shrink the other.

Setback, Height, and Size Standards

Setbacks

Local agencies cannot require side or rear setbacks greater than four feet for a new ADU.⁵ On small lots where five- or ten-foot setbacks would leave no buildable footprint, this rule is what makes construction feasible. Conversions get an even better deal: if you’re turning an existing legally permitted structure like a garage into an ADU, no additional setback requirements apply beyond the building’s current footprint.²

Height

These are floors, not ceilings. Local agencies must allow at least:

16 feet for a detached ADU on any lot with an existing or proposed single-family or multifamily dwelling.
18 feet for a detached ADU on a lot within a half-mile walking distance of a major transit stop or high-quality transit corridor, plus an additional two feet to match the roof pitch of the primary dwelling.
18 feet for a detached ADU on a lot with an existing or proposed multifamily, multistory dwelling.
25 feet (or the local zoning height for the primary dwelling, whichever is lower) for an attached ADU. Local agencies must allow attached ADUs to reach at least two stories.⁵

The 25-foot allowance is for attached units only. A detached backyard ADU near a train station tops out at 18 feet plus the two-foot roof-pitch bonus. If a detached two-story ADU fits these height limits and meets building code, the local agency cannot deny the application on the grounds that primary dwellings in the zone are limited to one story.²

Unit Size and the 750-Square-Foot Fee Threshold

Cities can set minimum and maximum sizes, but state law fences both ends. A local maximum cannot fall below 850 square feet for a studio or one-bedroom, or below 1,000 square feet for an ADU with two or more bedrooms.⁵ Separately, lot coverage and floor area ratio rules cannot be applied in a way that blocks construction of at least an 800-square-foot ADU with four-foot side and rear setbacks.² So even on a heavily built-out lot, you’re entitled to an 800-square-foot unit regardless of what a strict FAR calculation would produce.

ADUs of 750 square feet or less are fully exempt from impact fees charged by local agencies, special districts, and water corporations.² For larger units, impact fees must be calculated proportionally to the size of the primary dwelling instead of charged as a flat fee. Staying at or under 750 square feet can save thousands of dollars upfront, which is why so many ADU plans cluster right at that threshold.

Parking

Parking mandates killed more ADU projects than any other regulation before the state stepped in. Local agencies cannot impose any parking requirement on an ADU located within a half-mile walking distance of public transit, including bus stops, train stations, and ferry terminals.² Parking exemptions also apply when the ADU sits within an architecturally or historically significant district, or when on-street permits are required but not available to the ADU occupant.

SB 1211 closed the last big loophole. When a garage, carport, or covered parking structure is demolished or converted to build an ADU, the local agency cannot require replacement of the lost parking spaces.⁴ The primary residence can lose its off-street parking entirely as a result of ADU construction, and the city has no authority to demand it be restored.

Ministerial Approval and the 60-Day Clock

ADU applications go through ministerial review. The local agency checks the plans against objective standards and either approves or denies. No public hearing, no neighborhood input, no discretionary judgment about neighborhood character, and no environmental review under the California Environmental Quality Act.² If the plans meet the standards, the permit must issue.

The permitting agency has 60 days from receiving a complete application to approve or deny, assuming the lot already has an existing single-family or multifamily dwelling.² Miss the deadline and the application is deemed approved by operation of law. In jurisdictions with backlogged planning departments, applicants have used this provision to force permit issuance.

A denial must come in writing and identify every deficient item plus how to fix each one. A 2026 update to the law also requires permitting agencies to offer a formal appeal process for denials or incompleteness determinations, with a final written decision due within 60 business days of the appeal being filed.²

Owner-Occupancy, Rentals, and Separate Sale

No Owner-Occupancy Requirement for Standard ADUs

Local agencies cannot require owner-occupancy for a standard ADU, and they cannot impose deed restrictions to enforce one either. Government Code Section 66315 prohibits both.² An investor who owns a rental property with a single-family home can build an ADU and rent both units without ever living on the property. Junior ADUs work differently: the property owner must occupy either the primary residence or the Junior ADU as their principal home.⁶

Minimum Rental Term

State law requires any ADU be rented for terms longer than 30 consecutive days.³ That effectively bars short-term vacation rentals through platforms like Airbnb unless the stay runs longer than 30 days. Some cities layer additional short-term rental rules on top of this floor, so check local ordinances before listing.

Selling the ADU Separately

An ADU generally cannot be sold or conveyed separately from the primary residence. Assembly Bill 1033, effective in 2024, allows local agencies to adopt ordinances permitting separate sale of an ADU as a condominium under the Davis-Stirling Common Interest Development Act. The process requires a safety inspection, compliance with the Subdivision Map Act, and written consent from every existing lienholder before a condominium plan can be recorded. This option exists only if your city has opted in.

HOA Restrictions

Homeowners associations in planned developments cannot block ADU construction. Civil Code Section 4751 voids any CC&R provision that would prevent the construction of an ADU or Junior ADU. An HOA can still conduct architectural review, but cannot impose restrictions that unreasonably increase construction costs, effectively prohibit building, or eliminate the ability to construct an ADU. State setback and parking protections override conflicting HOA rules. If association rules require cars to be parked in garages, that rule cannot be used to stop a garage conversion.

HOAs keep some authority over rental terms. Since state law already sets a 30-day minimum, associations can adopt the same restriction in their governing documents for community-level enforcement. Where a lot has both an ADU and a Junior ADU, the HOA can require owner-occupancy consistent with the state’s JADU rules.

Fire Sprinklers

An ADU needs fire sprinklers when the primary dwelling already has a sprinkler system. Building a new ADU by itself does not trigger a requirement to retrofit sprinklers into the existing primary home.⁷ For entirely new construction where the primary dwelling is also being built from scratch, automatic residential sprinkler systems are required in all dwellings, including any ADU on the lot. The applicable standard for detached ADUs on single-family lots is typically NFPA 13D, which covers one- and two-family dwellings, though local amendments can vary. Residential sprinkler installation generally runs $1 to $3 per square foot, so an 800-square-foot ADU absorbs a few thousand dollars rather than a project-killing sum.

Financing an ADU

FHA 203(k) Rehabilitation Loans

The FHA 203(k) program explicitly lists single-family homes with eligible accessory dwelling units as an acceptable property type.⁸ The loan bundles purchase or refinance with renovation costs into a single mortgage. The Standard 203(k) handles major structural work like a new ADU; the Limited 203(k) is for smaller improvements. Both carry FHA’s lower down payment requirements versus conventional construction loans.

Conventional Loans With Projected ADU Rent

Fannie Mae lets borrowers count projected rental income from an existing ADU toward qualifying for a conventional mortgage, subject to conditions. The property must be a one-unit principal residence, and ADU rental income can supply up to 30 percent of the borrower’s total qualifying income.⁹ The transaction must be a purchase or limited cash-out refinance, and only one ADU’s rental income qualifies. The lender will require an appraisal with a Single-Family Comparable Rent Schedule (Form 1007) to document the ADU’s income potential.

VA Loans

Veterans using VA-backed loans can buy properties that include an ADU, though the VA calculates entitlement using the one-unit conforming loan limit even when the property contains additional units.¹⁰ Most eligible borrowers pay no down payment within the loan limit.

1
California Legislative Information. California Government Code 66310
2
California Department of Housing and Community Development. Accessory Dwelling Unit Handbook
3
California Legislative Information. California Government Code 66323
4
LegiScan. California Senate Bill 1211 – Land Use: Accessory Dwelling Units: Ministerial Approval
5
California Legislative Information. California Government Code 66321
6
California Department of Housing and Community Development. Frequently Asked Questions: Junior Accessory Dwelling Units
7
California Department of Housing and Community Development. Accessory Dwelling Unit (ADU) Information Bulletin
8
U.S. Department of Housing and Urban Development. 203(k) Rehabilitation Mortgage Insurance Program
9
Fannie Mae. Rental Income
10
Veterans Affairs. VA Home Loan Entitlement and Limits