Santa Ana | ADUs and SB 9

Santa Ana ADUs and SB 9 Two-Unit Projects: City Rules and the State Laws That Override Them

An accessory dwelling unit (ADU) is a second, smaller home on a lot with a house or apartment building. A junior ADU is a unit of no more than 500 square feet inside a single-family house. An SB 9 two-unit project uses the 2021 state law that lets an owner build two main homes on a single-family lot. Santa Ana writes its own rules for all three in Chapter 41 of the Municipal Code, Supplement 33 Update 1. Several of those rules are stricter than state law, and where they conflict, the state law controls. This page sets out both. The Santa Ana overview sums up the guide.

Santa Ana's ADU Ordinance

Santa Ana's ADU rules are Sections 41-194 to 41-194.7. The current text dates from Ordinance NS-2986 of April 7, 2020, with changes by NS-3030 of December 6, 2022 and NS-3076 of February 4, 2025. Section 41-194 says the rules apply to ADUs and junior ADUs "as defined in this section and in California Government Code sections 66310, et seq."

ADUs and junior ADUs "may be permitted in all zoning districts where residential or mixed-use development is permitted" (Section 41-194.2 (A)). The Executive Director of the Planning and Building Agency approves or denies each permit as a ministerial decision, which means staff check the plans against fixed rules with no hearing and no discretion. A non-refundable review fee must be paid. Section 41-194.6 gives one route to challenge a denial: an application for a minor exception, a small change to a standard decided under Article V.

The number of units depends on what stands on the lot. A lot with a house, or with several detached houses, "shall not be permitted more than one (1) ADU" (Section 41-194.2 (C)). A house lot may also have one junior ADU, which may be carved from the house or an attached garage; a lot with several detached houses may not have one (Section 41-194.2 (G)). An apartment lot may convert unused space into at least one ADU and up to 25 percent of its homes, and may add up to eight detached ADUs, never more than the existing homes (Sections 41-194.2 (D) and (E)). A lot planned for a new apartment building may add up to two detached ADUs (Section 41-194.2 (F)). The City's ADU standards page gives an example: "An existing 12 unit apartment complex can develop a maximum eight (8) detached units, with an additional three (3) conversion units (12 x 25%) from existing, attached non-habitable space, for a total of eleven (11) ADUs."

An ADU may be sold apart from the house only when a qualified nonprofit built both under Government Code 65852.26 and signs an affordable housing agreement with the City (Section 41-194.2 (H)). ADUs on historic properties must follow the federal Secretary of the Interior's standards for historic buildings (Section 41-194.4).

The ADU Size, Height and Setback Table

Sources: Santa Ana Municipal Code Section 41-194.3 and notes (A) to (M); Government Code 66314, 66321 and 66322.

The notes under the table carry the details. An attached ADU "shall not exceed fifty (50) percent of the size of the habitable space of the primary residence," but it may go past that to reach 800 square feet, and never past 1,000 (note A). An existing accessory building may become an ADU and grow by up to 150 square feet without meeting the rules for new ADUs (note C). Converting space inside the house or an existing accessory building is exempt from the size, height, setback, coverage, open space and separation limits (notes D to K). Height for a detached ADU is measured "from the lowest adjacent grade of the structure to the highest point of the roof" (note E).

Several limits give way so that an 800 square foot ADU always fits. The ADU may reach into the front setback, exceed the district's lot coverage, shrink the 1,200 square foot open space and come closer than 15 feet to the house "to permit an ADU up to eight hundred (800) square feet in size" (notes F, H, I and K). That matches Government Code 66321, which bars limits on "lot coverage, floor area ratio, open space, front setbacks, and minimum lot size" that would block "an accessory dwelling unit with at least 800 square feet of interior livable space and with four-foot side and rear yard setbacks." The R1 rear yard and accessory building limits also exclude ADUs (Sections 41-236 and 41-239).

Parking is one space per ADU, which may be tandem, one car behind another in a driveway. Note (L) lists seven cases with no parking at all, including an ADU "within one-half (½) mile walking distance of public transit," in "an architecturally and historically significant historic district," inside the house or an existing accessory building, near a car share vehicle, or "constructed as a studio, without bedrooms." When a garage or parking space is converted or torn down for an ADU, "replacement of those off-street parking spaces shall not be required" (note M). The City page says "No parking is required for a JADU."

Where the ADU Code and State Law Differ

Santa Ana's ADU text was last changed in February 2025. State ADU law was amended again by SB 543 and AB 1154, effective January 1, 2026. Where a city ADU rule is stricter than state law, state law controls. Four points matter.

• How many ADUs on a house lot. Section 41-194.2 (C) says a house lot "shall not be permitted more than one (1) ADU." Government Code 66323 requires ministerial approval of "any combination" of one ADU and one junior ADU within the house or an existing accessory structure, and "One detached, new construction, accessory dwelling unit," which the city may limit to 800 square feet. So a house lot may have a converted ADU, a junior ADU and a new detached ADU.
• Owner occupancy for junior ADUs. Section 41-194.5 requires a covenant that the house or the junior ADU be owner-occupied, and the City page says "Owner occupancy is required." Government Code 66333 says owner occupancy "shall not be required if the junior accessory dwelling unit has separate sanitation facilities."
• Incomplete applications. Section 41-194.2 (B) says incomplete applications "will be rejected." Government Code 66317 requires a written decision on completeness within 15 business days and a list of what is missing, then a decision within 60 days of a complete application when a home stands on the lot.
• ADUs with Transit Zoning Code duplexes. Section 41-2031 (j) says "Accessory dwellings shall not be permitted" with the duplex, triplex and quadplex building type, while Section 41-2020 says ADUs follow Section 41-194. Government Code 66323 requires ADUs on lots with existing or proposed multifamily buildings.

Fees follow state law too. Government Code 66311.5 bars impact fees on an ADU of "750 square feet of interior livable space or less" and requires larger ADUs to be "charged proportionately in relation to the square footage of the primary dwelling unit." Santa Ana's fee schedule lists an ADU review at $1,940, an over-the-counter ADU review at $594 and a pre-approved plan review at $524. The City's ADU page offers pre-approved plans, ready-made designs for detached studio, one-bedroom and two-bedroom ADUs.

SB 9 Two-Unit Projects: Santa Ana Article XX, Division 3

Division 3 of Article XX, added by Ordinance NS-3013 of December 21, 2021, carries out Government Code 65852.21. A "two-unit project" means "the development of two (2) primary dwelling units or, if there is already a primary dwelling unit on the lot, the development of a second primary dwelling unit on a legally subdivided lot" (Section 41-2112). The applicant must hold "a certificate of compliance with the Subdivision Map Act" for the lot (Section 41-2113 (c)), and the Executive Director of Planning and Building approves or denies the project "ministerially, ... without discretionary review" (Section 41-2114).

Source: Santa Ana Municipal Code, Chapter 41, Article XX, Division 3 (Sections 41-2111 to 41-2117), Supplement 33 Update 1.

A lot that was not created by an urban lot split may have the two-unit project "plus any ADU or JADU that must be allowed under state law and the city's ADU ordinance" (Section 41-2115 (f)(1)(B)). An older house larger than 800 square feet stays at its size and "may not be expanded," and a smaller one may grow to 800 square feet. The project may not tear down more than 25 percent of the existing outside walls "unless the site has not been occupied by a tenant in the last three (3) years."

The design rules are long. A new home must match the existing one in "exterior materials, color, and dominant roof pitch." Shiny or mirror-like roofing is banned, outdoor lights must point down, and "No window or door of a dwelling that is constructed on the lot may have a direct line of sight to an adjoining residential property," though a fence, plants or privacy glass may screen it. Section 41-2115 (f)(9)(F) adds that any part of a home "less than thirty (30) feet from a property line that is not a public right-of-way line" must use high windows, with the glass at least 6 feet above the floor, or frosted glass. Common living space must be at least as large as the bedroom space, and water heaters and laundry may not sit outside the home.

The lot stays in one ownership. The homes "may not be owned or conveyed separately from each other," and condominiums are not allowed (Section 41-2115 (g)). Unless the lot came from an urban lot split, the owners "must occupy one (1) of the dwellings on the lot as the owners' principal residence and legal domicile." The recorded deed restriction bars rentals under 30 days and "requires that any net new unit created be deed restricted for affordable housing," with rentals to very low or low income households and sales to moderate income households.

Where Santa Ana's SB 9 Text and State Law Differ

Division 3 dates from 2021, and Government Code 65852.21 was last amended by SB 1426, effective June 30, 2026. Where they conflict, the statute controls. Ask the Planning Division how it applies Division 3 today.

• Uniform standards. The statute says a city "shall not impose objective zoning standards, objective subdivision standards, and objective design standards that do not apply uniformly to development within the underlying zone." Santa Ana's 800 square foot cap, the 30 foot window rule and the 22 foot height limit apply to SB 9 homes only.
• Owner occupancy and affordability. The statute's text for two-unit projects contains no owner occupancy requirement and no affordability covenant. Santa Ana requires both.
• Grounds for denial. Section 41-2116 allows denial for a specific adverse impact "on either public health and safety or on the physical environment." The statute allows denial only for a specific adverse impact "upon public health and safety."
• Deadline and old violations. The statute requires a decision "within 60 days" of a complete application, after which "the application shall be deemed approved." Division 3 sets only a 30-day notice of incompleteness, and Section 41-2115 (f)(11) approves a project only "if all nonconforming zoning conditions are corrected."
• Historic exclusion. The statute excludes historic districts and properties listed by state inventory or local ordinance. Section 41-2115 (d) also excludes a "structure of merit" judged by five criteria, which reaches buildings no ordinance has listed.

The lots and subdivisions page covers the urban lot split in Division 2, and the state SB 9 page and ADU law page explain the statutes.

Where to Go Next

Related on VanPlex: the California ADU law page, the SB 9 page and the Santa Ana overview.

Frequently Asked Questions

Official sources (checked October 2026)