Orange County ADU Requirements (2026): City-by-City Rules for Size, Height, Setbacks and Parking

What are the Orange County ADU requirements in 2026?

Answer capsule: Orange County ADU requirements come from three layers: California Government Code §§ 66310–66342 (the floor for every jurisdiction), the local code of your city or the County of Orange, and any overlay such as the Coastal Zone or a homeowners association. State law sets minimums a city cannot go below, including 800 square feet with 4-foot setbacks, a 60-day decision clock, and no impact fees for ADUs of 750 square feet or less.

Three numbers do most of the work on a typical lot. The first is the size cap. A city can set its own maximum for a detached ADU, but state law says it can't be lower than 850 square feet, or 1,000 square feet for a unit with more than one bedroom (Gov. Code § 66321(b)(2) (opens in a new tab)). The state ceiling for a detached ADU is 1,200 square feet (§ 66314(d)(5) (opens in a new tab)). The second is the setback. No city can ask for more than 4 feet from the side and rear lot lines for a new ADU, and a conversion of an existing structure needs no new setback (§ 66314(d)(7)). The third is height. A city must allow at least 16 feet for a detached ADU, 18 feet near major transit, and 2 more feet to match the main house's roof pitch (§ 66321(b)(4)).

Cities can allow more than the floor, and several do. Costa Mesa's code permits a new ADU up to 27 feet or two stories if five conditions are met. Santa Ana allows a detached ADU up to 20 feet or two stories.

The catch. The floor is guaranteed, but the city's own page may not say so. HCD has told Irvine, Costa Mesa and Anaheim that parts of their ordinances conflict with state law, and Newport Beach's handout says its adopted code is out of date. The number on a city website can be lower than the number you're entitled to. We show how to handle that in the section on conflicts, and every row of the table above names the document it came from so you can check it.

Limits to know: the state floor is not unconditional. The statute ties these standards to a qualifying lot (zoned to allow a home, with an existing or proposed dwelling) and still lets agencies apply building, fire and other health and safety codes. Coastal Zone review, fire hazard areas and site conditions can also shape what gets approved. Ask your planner how those apply to your parcel.

Which ADU rulebook applies to your Orange County address?

Answer capsule: The rulebook that applies is the one for the jurisdiction that issues building permits for your address. Incorporated cities such as Irvine, Anaheim, Santa Ana, Costa Mesa, Garden Grove, Huntington Beach and Newport Beach run their own permit counters. Unincorporated areas are handled by OC Development Services at the County of Orange.

How to tell which one you are:

1. 1Search your address on your city's permit or zoning lookup. If no city claims it, the County of Orange is your permit office.
2. 2Look at your mailing address versus your jurisdiction. A “Costa Mesa” or “Irvine” mailing address does not always mean the property is inside that city's limits. The County's flyer covers properties outside incorporated cities.
3. 3Call the planning counter. Irvine's planning team is at planning@cityofirvine.org or 949-724-6308. Huntington Beach's permit center lists 714-536-5511. Anaheim lists ADUAnaheim@anaheim.net.

Our free ADU planning report can help you think through state-level options and broad cost ranges once you know your rulebook. It does not determine your jurisdiction or check your parcel, so use the steps above to confirm which office issues your permit first.

For the statewide picture, including cities outside Orange County, read our California ADU laws guide. For builder comparisons, see our Orange County ADU builders guide. This page covers rules only.

What does California law guarantee in every Orange County city?

Answer capsule: California's ADU statute, Government Code §§ 66310–66342, requires every Orange County city and the County to approve qualifying ADU permit applications ministerially, meaning without a public hearing, and to decide a complete application within 60 days (§ 66317). It also sets a floor of 800 square feet with 4-foot setbacks (§ 66321(b)(3)), height minimums of 16 to 25 feet (§ 66321(b)(4)), and a ban on impact fees for ADUs of 750 square feet or less (§ 66311.5(c)).

The statute was renumbered on March 25, 2024 (SB 477), and some sections were moved again on January 1, 2026 (SB 543). Old city pages that cite Government Code § 65852.2 are citing a section that no longer exists. Here is what each part of the current statute does for you, decoded.

JADU means junior accessory dwelling unit: a unit of up to 500 square feet inside an existing or proposed single-family home. A ministerial approval means staff checks your plans against written standards and approves or denies, with no hearing.

What do the rules say city by city?

Answer capsule: Orange County cities set different size, height and parking rules above the state floor. A detached ADU is capped at 1,000 square feet in Santa Ana and 1,200 in Anaheim, Costa Mesa and the unincorporated County, while Garden Grove caps studios and one-bedrooms at 850. Irvine and Huntington Beach rely directly on state law.

Unincorporated Orange County (County of Orange)

The County's flyer, revised January 2026, covers properties outside incorporated cities. It says a single-family property can have up to three ADUs or JADUs for a total of four dwellings on the lot: one detached ADU, one converted ADU and one JADU, citing Government Code § 66323. A detached ADU can be up to 1,200 square feet with 4-foot side and rear setbacks. A front-setback encroachment is allowed only to the extent needed to fit an 800-square-foot ADU, and then no closer than 4 feet to the front property line. Heights follow § 66321(b)(4): 16, 18 or 25 feet. Parking is one space per ADU unless an exemption applies, such as being within half a mile walking distance of public transit, being a studio, or being a garage conversion. JADUs need no parking.

Other County conditions: the unit can't be used for short-term rentals and must be rented for 30 days or more, and the applicant must show proof of adequate sewer service. You apply through the County's myOCeServices portal. The County also runs a Pre-Approved ADU Plans Program for new detached ADUs, described in the pre-approved plans section below.

Irvine

Irvine's Zoning Code now says, in full, that accessory dwellings “shall be permitted and regulated in compliance with Chapter 13 of Division 1 of Title 7 of the California Government Code (Section 66310 et seq.), as may be amended from time to time.” City Council adopted that wording on September 9, 2025 (Ordinance No. 25-22), replacing Chapter 3-26's local standards. In practice, the size, height, setback and parking rules in the state table above are Irvine's rules.

Irvine's ADU page lists what to file: a completed Residential Accessory Dwelling Unit application and an ADU Verification Form, building plans and calculations, a development standards checklist, a hold-harmless affidavit covenant that is notarized and recorded with the County of Orange Recorder, a developer deposit form, a school fee determination form, a transportation corridor agency form and an address application. You submit through the IrvineReady online permit portal, and staff review the package for completeness in approximately two business days, then email a link to pay fees.

Anaheim

Anaheim's Table 38-A in Municipal Code § 18.38.015 allows a detached ADU of up to 1,200 square feet, a minimum unit size of 150 square feet, 4-foot side and rear setbacks, and a detached height of 18 feet plus 2 feet for roof pitch or the main dwelling's height, whichever is greater. A detached ADU larger than 800 square feet needs 10 feet of separation from the main dwelling. On a single-family lot the code allows one ADU within the existing home or an accessory structure, one new ADU and one JADU, with no more than four units on the lot in total.

The same table says a detached ADU must sit no closer to the front property line than the front-most wall of the main dwelling, unless it is a garage, carport or covered-parking conversion. HCD flagged that language, as we explain in the conflicts section. Parking follows the city's residential parking section (18.42.030), and a garage that is converted or demolished for the ADU does not have to be replaced.

Anaheim also runs ADU Express for properties that pass its eligibility tool: you choose a pre-approved plan, call Anaheim Public Utilities to schedule a free meter spot (the city asks you to request a 400 amp, multi-meter location), meet staff to build your site plan, and, after fees and school fees are paid, the city says staff “should be able to issue your approved building permit, all within one day.” Anaheim lists ADUAnaheim@anaheim.net for questions.

Santa Ana

Santa Ana's ADU rules are in Municipal Code Article II of Chapter 41, §§ 41-194 to 41-194.3, as amended by Ordinance NS-3076, which the City Council adopted on February 4, 2025 to align with SB 1211. Table 41-194.3 sets ADU size at 220 to 1,000 square feet for attached and detached units and 500 for a JADU; detached height at 20 feet or two stories, measured from the lowest adjacent grade to the highest point of the roof; and 4-foot side, street-side and rear setbacks. Separation is 15 feet from the primary building for a detached ADU and 5 feet from accessory buildings. Parking is one space, tandem allowed, with exemptions listed in the table's notes, including studios and ADUs within the existing home.

The code lets an ADU of up to 800 square feet encroach into the front setback and exceed lot coverage, and it exempts conversions of existing structures from size, height, setback and lot-coverage limits. Section 41-194.2 says a single-family lot is “not permitted more than one (1) ADU” and one JADU. Compare that with the combination state law requires a city to allow (§ 66323(a)(1)–(2)), and ask the planning counter how the city applies it to a conversion plus a new detached unit.

Costa Mesa

Costa Mesa's § 13-35 allows, on a single-family lot, one detached new-construction ADU, one conversion ADU and one JADU. A detached ADU can be up to 1,200 square feet. An attached ADU can be the greater of 50 percent of the existing home or 1,000 square feet. The city allows ADUs as small as 150 square feet. Side and rear setbacks are 4 feet, with none for conversions or for rebuilding in the same footprint. The code sets a 6-foot minimum distance between a detached ADU and other structures, unless the California Building Code says otherwise.

On height, no new ADU can exceed 27 feet or two stories. A second-floor ADU or a two-story ADU is allowed on a lot with an existing lawful dwelling only if all five conditions are met, including a 25-foot distance from the front property line for second-floor portions, an interior or compliant stairwell, and no side-facing second-floor windows within 25 feet of a neighbor unless the sill is at least 5 feet high. Parking is optional: the code says the owner “may provide parking,” and replacement parking for a converted garage is not required. The code bars rentals under 31 days.

Garden Grove

Garden Grove's Chapter 9.54, last amended by Ordinance 2966 on August 12, 2025, caps a detached ADU at 850 square feet for a studio or one bedroom and 1,200 square feet for two or more bedrooms. An attached ADU is limited to 850 square feet or 50 percent of the primary dwelling (whichever is less) for a studio or one bedroom, and 1,200 square feet or 50 percent for two or more bedrooms, though a primary dwelling under 1,600 square feet can still support an attached ADU of up to 800 square feet. Detached height is 16 feet, rising to 18 feet within half a mile walking distance of a major transit stop or high-quality transit corridor, or on a multistory multifamily lot. Side and rear setbacks are 4 feet, and a detached ADU needs 6 feet from the primary dwelling and other structures.

A new attached or detached ADU needs one off-street space, which can be in a setback area or tandem on a driveway, unless an exemption applies, such as being within half a mile walking distance of public transit. The code prohibits rentals under 30 days, does not require owner occupancy for an ADU, and does require it for a JADU.

Huntington Beach

Huntington Beach's ADU page says its local ADU section (Zoning and Subdivision Ordinance § 230.10) “is no longer in effect” after the 2020 state laws, that the city provides ministerial review for all ADUs and JADUs, and that Coastal Zone projects may need a coastal development permit. The city offers one pre-approved plan under AB 1332: a one-story, detached, 490-square-foot ADU. The city says modifications to the plan are not allowed. The permit center's phone number is 714-536-5511.

Two Huntington Beach details are worth a call. The city's permit issuance page says additional development impact fees apply to “new homes, ADUs' and additions over 500 sf.” The wording doesn't say whether the 500-square-foot threshold covers ADUs, and state law bars impact fees on an ADU of 750 square feet or less (§ 66311.5(c)). Ask the city what it charges at your planned size. The city's plan review page also says the 2025 California Building Standards Code took effect on January 1, 2026, and that applications still incomplete after March 31, 2026 are voided and must be resubmitted under the new code.

Newport Beach

Newport Beach's ADU summary, revised April 19, 2022, says ADUs are regulated by Municipal Code §§ 20.48.200 and 21.48.200 and reviewed through a Zoning Clearance within 60 days of a complete application. It lists a detached ADU cap of 850 square feet for a studio or one bedroom and 1,000 square feet for two bedrooms, a 16-foot height limit, and 4-foot side and rear setbacks or the base zone's setback, whichever is less. A Coastal Development Permit may also be required in the Coastal Zone.

The handout is candid about its age. A footnote says “Current adopted code is out of date” regarding the rule that lets an ADU and a JADU share a lot, which state law allowed from January 1, 2021. Treat Newport Beach's handout as a starting point and confirm current standards with a planner before you design.

What happens when a city's rules and state law disagree?

Answer capsule: When a local ADU ordinance conflicts with state ADU law, the state law controls, and HCD can issue written findings telling the city to amend its ordinance (Gov. Code § 66326). HCD has done this for three of the Orange County cities on this page: Costa Mesa (September 11, 2024), Irvine (January 7, 2025) and Anaheim (March 24, 2025).

Here is what each letter reviewed, and what it means for you.

An HCD letter does not change your permit overnight. It tells you which parts of a local page deserve a second look. Our reading of the pattern: the numbers most likely to be off are the ones that restrict by percentage of the home, front setback, building separation, and one-ADU-per-lot wording. State law forbids those restrictions when they would stop an 800-square-foot ADU with 4-foot setbacks (§ 66321(b)(3)).

We can't tell you which version a given plan checker will apply to your lot, and some of the city pages we read were last revised years ago. What we can tell you is how to ask. Cite the state section, ask the planner to confirm in writing which standard applies, and keep the 60-day clock in mind: a city that misses it has approved your application by default (§ 66317(a)(3)). If a city denies an application, state law requires a written list of what's defective and how to fix it within that 60 days (§ 66317(b)), and a written appeal process (§ 66317(d)).

Limits to know: the 60-day clock runs from a complete application and has statutory exceptions (for example, it can be tolled at the applicant's request or when the ADU is submitted with a new primary home). Deemed approval does not waive building code compliance. Get advice from a land-use attorney before relying on it.

Owners with an older unit that was never permitted should also read our guide to legalizing an unpermitted ADU in California.

Do Orange County coastal ADUs need a coastal development permit?

Answer capsule: Possibly. State ADU law does not override the California Coastal Act, so an ADU in the Coastal Zone can need a coastal development permit (CDP) in addition to the building permit. Since AB 462 took effect on October 10, 2025, the local government must approve or deny the CDP within 60 days of a complete application, without a public hearing, at the same time as the ADU permit (Gov. Code § 66329 (opens in a new tab)).

If your city has no certified local coastal program, the California Coastal Commission makes the decision within the same 60 days, and a missed deadline means the application is deemed approved (§ 66329(b)). A decision by the local government is not appealable to the Commission under Public Resources Code § 30603 (§ 66329(c)).

Coastal cities on this page mention the requirement directly. Huntington Beach says Coastal Zone projects may need a coastal development permit, and Newport Beach's handout says the same. Ask your planner early whether your parcel is in the Coastal Zone, because the coastal review happens alongside, not after, the ADU review.

Can an HOA block an ADU in Orange County?

Answer capsule: No, not outright. California Civil Code § 4751 (opens in a new tab) voids any HOA covenant or governing-document provision that effectively prohibits or unreasonably restricts an ADU or JADU on a single-family lot that meets state ADU law. An HOA can still impose reasonable restrictions that don't unreasonably increase the cost to build or effectively prohibit the unit.

Two practical points. “Reasonable” is the fight, so ask for the HOA's architectural guidelines in writing before you hire a designer. And § 4751 applies to lots zoned for single-family residential use, so an HOA rule for a condo or townhome building is a different question. For the statewide version, see our California ADU laws guide.

Are there pre-approved plans or fast-track ADU programs in Orange County?

Answer capsule: Yes, in several places. Anaheim's ADU Express offers one-day building permit issuance for eligible properties using a pre-approved plan. Huntington Beach offers a single pre-approved 490-square-foot plan. The County of Orange offers six pre-approved detached plans from 393 to 1,200 square feet, and Irvine lists a pre-approved plans program on its ADU page.

A pre-approved plan is a design the city has already reviewed, so you skip some design review. It doesn't skip the site-specific parts: utilities, fees, setbacks and the Coastal Zone still apply. Huntington Beach's page is blunt that the plan cannot be modified. If your lot or your needs don't fit a 490-square-foot box, you're on the standard track.

For plan libraries elsewhere in Southern California, our pre-approved ADU plans guide is the place to start.

How does the Orange County ADU permit process work, and how long does it take?

Answer capsule: The process runs: confirm jurisdiction and zoning, design the ADU, submit through your city's or the County's online portal, answer a completeness review, then plan check and permit. State law gives the agency 15 business days to tell you whether the application is complete and 60 days to decide a complete one (Gov. Code § 66317(a)(2)–(3)). Construction time is separate.

1. 1Confirm your jurisdiction and zoning. See above.
2. 2Choose a path. Pre-approved plan or custom plan.
3. 3Gather forms. Irvine's list is the longest we found, and it includes a notarized and recorded hold-harmless covenant. The County asks for proof of adequate sewer service.
4. 4Submit online. Irvine uses IrvineReady, Huntington Beach uses its HB ACA portal, and the County uses myOCeServices. Anaheim staff upload materials to an online portal during the ADU Express meeting.
5. 5Pass the completeness check. If the agency says the application is incomplete, it must list what's missing and can't later demand items that weren't on the list (§ 66317(a)(2)(B)–(D)).
6. 6Plan check and permit. Santa Ana's code assigns ministerial approval to the executive director of the planning and building agency. Costa Mesa's code cites § 66317 for approval without a hearing.
7. 7Pay fees. School fees and city fees come due before the permit is issued. For impact fees, check § 66311.5(c) against what your city lists.
8. 8Build and inspect. Anaheim points applicants to its automated inspection scheduling system.

Our ADU permit process guide walks through the same steps for the whole state, and our ADU cost calculator gives you a budget range before you commission drawings.

Which Orange County cities does Nest Tiny Homes list?

Answer capsule: Nest Tiny Homes' service-area page lists these Orange County cities: Newport Beach, San Clemente, Laguna Beach, Huntington Beach, Santa Ana, Garden Grove, Brea, Aliso Viejo, Dana Point, Costa Mesa, Irvine, Westminster, Fullerton and San Juan Capistrano, plus Corona, which is in Riverside County. Anaheim and unincorporated Orange County are not on the list.

Nest describes itself as a design-build firm for detached ADUs, attached ADUs and garage conversions. It's an option if you want one company to handle design, permits and construction in a listed city. It isn't the only option, and we compare eight builders and prefab companies, with prices and licensing, in our Orange County ADU builders guide.

If your city isn't on a builder's list, or you want state-level context and a broad cost range before you talk to anyone, start with the free planning report instead. It won't check your lot; your city or the County does that.

What should you ask the planning counter before you pay for plans?

Answer capsule: Ask ten questions before paying a designer: which jurisdiction issues the permit, which ordinance version applies, whether a conversion plus a new detached unit is allowed together, the size, height and setback numbers for your zone, whether the Coastal Zone applies, whether an HOA reviews it, the parking rule for your address, the impact fees at your planned size, whether a pre-approved plan fits, and the current completeness and review timeline.

1. 01Which office issues the permit for my address: a city or the County?
2. 02Which version of the ADU ordinance do you apply today, and does it reflect Government Code §§ 66310–66342 as renumbered?
3. 03Can I build a conversion ADU and a new detached ADU plus a JADU on my lot, as § 66323 describes?
4. 04What are the maximum size, height and setbacks for a detached ADU in my zone?
5. 05Is my parcel in the Coastal Zone, and does it need a coastal development permit?
6. 06Is there parking required at my address, or does an exemption in § 66322 apply?
7. 07What impact fees, school fees and utility connection charges will apply at my planned square footage?
8. 08Does a pre-approved plan fit my lot and my goals?
9. 09Does the city treat a garage conversion differently from a new build?
10. 10How long does your completeness review take right now, and who is my contact?

Print this list, write the answers in the margin and put the date next to each. If your answers contradict this page, trust the city's current written answer and tell us through our corrections page.

What we verified

Methodology

We pulled each jurisdiction's own published rule, not a third-party summary, and recorded the document name and date next to every number. State law came from the statute text on leginfo.legislature.ca.gov. Where a city page and the statute differ, we show both and don't pick a winner on your behalf. We did not use builder blogs for any rule. Our editorial judgments, such as which restrictions seem most likely to be off, are labeled as ours. We plan to re-check this page quarterly and whenever a city or HCD publishes a change. Corrections go through our corrections page.

Sources

• California Government Code §§ 66311.5 (opens in a new tab), 66314 (opens in a new tab), 66317 (opens in a new tab), 66321 (opens in a new tab), 66322 (opens in a new tab), 66323 (opens in a new tab), 66329 (opens in a new tab): leginfo.legislature.ca.gov
• California Civil Code § 4751 (opens in a new tab): leginfo.legislature.ca.gov
• County of Orange, OC Public Works / OC Development Services, “Accessory Dwelling Units (ADU) – Single-Family” (rev. January 2026) (opens in a new tab); “Pre-Approved Accessory Dwelling Unit (ADU) Plans” (opens in a new tab)
• City of Irvine, Request for City Council Action, September 9, 2025, Ordinance Nos. 25-22 and 25-23: irvine.granicus.com (opens in a new tab)
• City of Irvine, “Project: Constructing an Accessory Dwelling Unit (ADU)” (opens in a new tab)
• City of Anaheim, Municipal Code § 18.38.015 (opens in a new tab) and “ADU Express Process” (opens in a new tab)
• City of Santa Ana, Ordinance No. NS-3076: Municode (opens in a new tab)
• City of Costa Mesa, Municipal Code § 13-35: Residential Districts (opens in a new tab)
• City of Garden Grove, Municipal Code Chapter 9.54 (opens in a new tab)
• City of Huntington Beach, “Accessory Dwelling Units” (opens in a new tab), “Permit Issuance Process,” “Plan Review Process”: huntingtonbeachca.gov
• City of Newport Beach, “Accessory Dwelling Unit Ordinance Summary,” revised April 19, 2022: newportbeachca.gov (opens in a new tab)
• California HCD, ordinance review letters to Costa Mesa (Sept 11, 2024) (opens in a new tab), Irvine (Jan 7, 2025) (opens in a new tab) and Anaheim (Mar 24, 2025) (opens in a new tab)
• Nest Tiny Homes, service areas: via our tracked link Nest Tiny Homes service areas (affiliate link)

Frequently asked questions

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