California ADU Setback, Height, and Parking Rules

A city can be more generous than that floor. It cannot be stricter where the statute sets a maximum. What follows is the rule a city has to follow for ADUs and junior ADUs on single-family and multifamily lots: setbacks, height, the size a coverage limit cannot block, parking, sprinklers, and the objective standards a city may still write. It is general information from the Government Code and HCD’s March 2026 ADU Handbook, checked November 5, 2026. Your planner, and a licensed designer you hire, still read the lot. The short checklist is the legal guide.

Two approvals, and they do not use the same ruler

Section 66323 is the list a city must approve ministerially even with no ADU ordinance. HCD calls these “66323 units.” The city cannot add an objective standard unless that section authorizes it. On a lot with a proposed or existing single-family home, the list is one ADU inside the house or an existing accessory structure, one junior ADU, and one new detached ADU. On a lot with an existing multifamily building, it is at least one ADU, and up to 25 percent of the existing units, inside space that is not already livable, plus up to eight detached ADUs, not more than the number of existing units. A proposed multifamily building gets up to two detached ADUs.

Section 66314 is the ordinance track: objective standards for parking, height, setback, landscaping, architectural review, and maximum size. They still have to clear section 66321. A conflicting ordinance loses. A city may always be less restrictive. Section 66325.

Side and rear setbacks

For an ADU that is not a conversion, section 66314(d)(7) says the required side and rear setback shall be no more than 4 feet. That is the most zoning can demand. Less, including zero, is allowed. The same sentence requires no new setback for existing living area that is converted, for an existing accessory structure that is converted, or for a new building in the same place and the same dimensions as an existing structure. That third case is the same-footprint rebuild. Move it or enlarge it, and the waiver ends. A detached garage and a shed are accessory structures.

A junior ADU stays inside the proposed or existing single-family residence, and an attached garage counts as part of that residence. It is not placed in a detached shed, so it takes no new yard. The junior ADU guide covers the 500-square-foot cap.

A conversion under section 66323(a)(1) needs its own exterior door. It may grow by no more than 150 square feet past an existing accessory structure, and only for ingress and egress. HCD’s example is a stair. The setback test for that unit is fire and safety, not a new 4-foot yard. Detached units on a multifamily lot also stay within 4 feet of the side and rear. If the existing building is already closer, the city cannot make you move it. Section 66323(a)(4). Four feet is zoning. The building and fire codes still apply, and HCD says a local distance rule cannot unreasonably restrict an ADU unless the code itself requires the distance. A passageway, a path clear to the sky from the street to the ADU door, shall not be required. Sections 66313(j) and 66314(d)(6).

Height: 16 feet, 18 feet, and 25 feet

The state does not cap height. It sets the lowest limit a city may write, in section 66321(b)(4). A city may allow taller. HCD’s March 2026 handbook restates the same floors. The new detached unit under section 66323 uses the detached rows. A conversion keeps the height of the building you started with.

The extra 2 feet only lets the ADU roof match the main roof, and only on the transit row. That row is a half-mile walk of a major transit stop or a high-quality transit corridor under Public Resources Code section 21155. A major transit stop, section 21064.3, is a rail or bus-rapid-transit station, a ferry terminal served by bus or rail, or two major bus routes running every 20 minutes or less in both peaks. A high-quality corridor is fixed-route bus service at least every 15 minutes in the peak. An hourly bus does not raise this floor. HCD names no official map. Ask the metropolitan planning organization, then the city.

HCD says a city cannot turn down a detached two-story ADU that fits the required height and the building code, only because the zone holds the main house to one story. For an attached unit, the handbook says two stories must be allowed when the height and the building standards can fit them. Section 66321(b)(4)(D) does not require a third story.

The 800-square-foot floor, coverage, and the front yard

Livable space, section 66313(e), is space for living, sleeping, eating, cooking, or sanitation. HCD counts bedrooms, bathrooms, kitchens, laundry, closets, and interior stairs. A garage is not living area. Section 66313(f).

Section 66321(b)(3) is the coverage rule. The city cannot use a separate zoning review, another size limit, a percentage of the main house, lot coverage, floor area ratio, open space, a front setback, or a minimum lot size to stop an ADU of at least 800 square feet of interior livable space with 4-foot side and rear setbacks. Section 66314(b)(1) also bars a minimum lot size outright.

A front setback can still exist. It cannot be why that 800-square-foot unit will not fit. HCD says the city may send an ordinance-track ADU to the backyard, and must allow the front setback if that is the only place the 800 square feet fit. On a 66323 unit, section 66323(b) bars a front-setback rule, and HCD says the new detached unit may sit in the front yard.

Keep three numbers apart. 800 square feet is what coverage and the front yard cannot block, and it is the cap a city may put on the new detached unit in section 66323(a)(2). The city may allow that unit to be larger. 850 square feet, or 1,000 with more than one bedroom, is the lowest maximum an ordinance may write. Section 66321(b)(2). Section 66314(d)(4) also caps an attached ADU at 50 percent of the existing main house, and HCD says that percentage still has to leave 850 square feet, or 1,000 for more than one bedroom. 1,200 square feet is the detached cap a 66314 ordinance must include, and the city may allow more. Sections 66314(d)(5) and 66325(b).

The city cannot set a minimum that prohibits an efficiency unit. Section 66321(b)(1). Health and Safety Code section 17958.1 lets a city allow an efficiency unit for no more than two persons, with at least 150 square feet. A 66323 conversion is the space you have, plus the 150-square-foot ingress expansion, and it is not subject to the size caps. Non-livable space in an existing multifamily building includes storage, boiler rooms, attics, basements, and garages. HCD says detached multifamily ADUs must be detached from the main building, and they may touch each other.

Parking

If the city requires parking, section 66314(d)(10)(A) caps it at one space per ADU or per bedroom, whichever is less. A studio adds no bedroom. HCD says guest parking shall not be required. Spaces may be tandem, cars lined up one behind another, and they must be allowed in a setback unless the city finds that infeasible for topography or fire and life safety. Sections 66313(n) and 66314(d)(10)(B).

Section 66322 applies with or without an ordinance. The city shall not impose any parking standard when:

1. The ADU is within a half-mile walk of public transit. Section 66313(m) means a bus, train, subway, or other fixed-route service that charges a set fare and is open to the public. A bus stop counts. This is wider than the major-transit-stop test used for the 18-foot height. Ask which stop the city will measure.
2. The ADU is in an architecturally and historically significant historic district. Ask if the city treats yours as one. A California Register design rule under section 66314(b)(1) is a separate question from this parking exemption.
3. The ADU is part of the proposed or existing primary residence or an accessory structure. Interior conversions and garage conversions land here.
4. On-street parking permits are required, and the city does not offer one to the ADU occupant.
5. A car-share vehicle is within one block. The statute does not turn “one block” into a number of feet. Ask how the city measures it.
6. The ADU application is filed with a new single-family or multifamily home on the same lot, and the ADU or the parcel also meets one of the five cases above. Filing with the new house is not, by itself, an exemption. Section 66322(a)(6). HCD reads it the same way.

HCD says a city may not impose parking on 66323 units, because section 66323(b) bars a standard the section does not authorize. A junior ADU ordinance shall not require additional parking. Section 66334(a).

Replacement parking is the garage rule. When a garage, carport, covered space, or uncovered space is demolished with the ADU, or converted to the ADU, the city shall not require those spaces to be replaced. Section 66314(d)(11). The demolition permit for a detached garage the ADU replaces is reviewed with the ADU and issued at the same time. No placard and no written notice, unless the lot is in an architecturally and historically significant historic district. Sections 66314(e) and (f). The construction steps are in the garage conversion guide.

Fire sprinklers follow the main house

Sprinklers shall not be required in an ADU if the primary residence does not need them, and the ADU shall not trigger sprinklers in the existing house. Section 66314(d)(12). Section 66323(d) says the same for an ADU or junior ADU, and says neither one triggers sprinklers in an existing multifamily building. HCD’s example: an older house that was never required to have sprinklers does not gain that duty because an ADU is added. If a later alteration already required sprinklers in the house, an ADU built after that alteration needs them too. For a fire ordinance, a junior ADU is not a separate new dwelling, though a city may adopt a fire rule that applies the same way to every single-family house in the zone. Section 66337.

What a city can still regulate

Objective means no personal judgment, and a benchmark you and the city can both check before you apply. Section 66313(i). A number, a listed color, a listed material. HCD’s examples of language a city may not use are “compatible with the neighborhood” and “high-quality materials.” Inside that line, a city may:

• Map where ADUs are allowed, based only on water, sewer, traffic, and public safety. Section 66314(a). HCD says that map cannot block 66323 units, and a fire-hazard map alone is not a ban. A safety limit needs findings.
• Set objective height, setback, landscape, design, and size rules inside the floors on this page, plus standards that protect a California Register property. Section 66314(b)(1).
• Keep front setbacks, coverage, floor area ratio, and open space on ordinance-track ADUs, if an 800-square-foot unit with 4-foot side and rear setbacks still fits.
• Require 66323 ADUs and junior ADUs to be rented for longer than 30 days. Sections 66323(e) and 66333(g). Section 66315 bars owner-occupancy as an added ADU standard. HCD notes a narrow exception when an ADU is sold separately under section 66341.
• Require health-officer sign-off on a private septic system, and a percolation test from the last five years, or ten if recertified. Sections 66314(d)(9) and 66323(f).
• Apply the building code. An ADU is not, by itself, a Group R occupancy change unless the building official writes a finding of a specific adverse health or safety impact. Section 66314(d)(8).

In the coastal zone, a certified local coastal program can require a deeper setback. Section 66329 leaves the Coastal Act in place. Bluff, wetland, and view standards are in the coastal zone guide. If the city’s ordinance was never sent to HCD, or the city never answered a finding that it is out of compliance, the ordinance is null and void and the state standards apply until a compliant ordinance is adopted. Sections 66316 and 66326. A junior ADU ordinance has the same duty under section 66333.5.

How to find the rule on your lot

The statute is the floor. The counter’s handout is how the city has tried to meet it. Before you pay for drawings, write down the handout’s side setback, rear setback, front setback, height, size cap, and parking line, and set them next to this page. A side yard over 4 feet, a detached height under 16 feet, a maximum under 850 square feet, or a demand for two ADU spaces is a question, not a number you have to draw. Email the planner: which track applies, 66323 or the ordinance; whether the ordinance went to HCD; and which stop or car-share spot they will accept for a parking exemption or the 18-foot floor. On a coastal lot, ask whether the local coastal program changes the setback.

Local pages on this site already do that comparison for some cities. Start at the city guide index. The Los Angeles guide follows ZA Memo 143 on the 800-square-foot detached unit, the 4-foot yards, and that city’s parking list. The Long Beach guide follows bulletin IB-PZ-001, including a rear setback to an alley centerline. The planning guide is what to measure before you draw. The glossary is the short definition of livable space, tandem parking, and ministerial review.

What changes on January 1, 2027

A permit filed this year uses the rules above. AB 956 (Quirk-Silva), Chapter 791, Statutes of 2026, was approved September 29, 2026, and the chaptered text has no urgency clause. As the 2026 law update explains, it takes effect January 1, 2027. Section 66323(a)(2) then requires two new detached ADUs on a single-family lot, still at 4-foot side and rear setbacks, with the city still allowed to cap each at 800 square feet and to apply the detached height floors. The city does not have to approve a junior ADU on a lot where those two have been built. Later paragraphs of section 66323 move down one letter. The yard, the utilities, and the fire separation still have to work.

SB 1117 (Cervantes), Chapter 809, Statutes of 2026, approved the same day, amends only section 66311.5, the impact-fee count. It does not change setbacks, height, or parking. The fee math is on the law update.

Questions homeowners ask

How close can a new California ADU sit to the side and rear lot lines?

For new construction, no more than 4 feet from the side or the rear. A conversion of existing space, and a same-size rebuild in the same place, takes no new setback.

Does a garage conversion need a new setback or replacement parking?

No new zoning setback if you stay inside the existing walls, and no replacement of the parking you convert or demolish. The building code still applies.

How tall can a California ADU be?

A city must allow at least 16 feet for a detached ADU, 18 feet near a major transit stop or a high-quality transit corridor (plus 2 feet to match the main roof), 18 feet on a lot with an existing or proposed multistory multifamily building, and 25 feet or the main house’s zoning height, whichever is lower, for an attached ADU. The city does not have to allow more than two stories.

Can lot coverage or a front setback block an 800-square-foot ADU?

No. Coverage, floor area ratio, open space, front setbacks, and minimum lot size cannot stop an 800-square-foot ADU with 4-foot side and rear setbacks. A 66323 unit is also free of standards that section does not authorize.

How much parking can a city require for an ADU?

One space per ADU or per bedroom, whichever is less. None within a half-mile walk of public transit, in a qualifying historic district, inside existing space, where the ADU occupant cannot get an on-street permit, or within a block of a car-share vehicle. HCD says 66323 units and junior ADUs are not charged a parking space.

Do I need fire sprinklers in the ADU?

Only if the primary residence is required to have them. The new unit does not, by itself, force sprinklers into the existing house.

Sources

Checked November 5, 2026, on leginfo.legislature.ca.gov and the March 2026 HCD handbook PDF.

• Gov. Code §66313. Livable space, living area, public transit, tandem parking, passageway, objective standards.
• Gov. Code §66314. Four-foot side and rear maximum, conversion and same-footprint waiver, one-space cap, no replacement parking, no passageway, sprinklers, 1,200-square-foot detached cap, 50-percent attached cap, garage demolition. Amended by Stats. 2025, Ch. 67, effective January 1, 2026.
• Gov. Code §66315. No added owner-occupancy standard. Rentals of 30 days or longer may be required.
• Gov. Code §66316 and §66326. Ministerial approval. An ordinance not submitted to HCD, or not defended after HCD’s findings, is null and void.
• Gov. Code §66321. The 800-square-foot floor, the 850/1,000 maximum-size floors, and the 16/18/25-foot height floors. Amended by Stats. 2025, Ch. 520, effective January 1, 2026.
• Gov. Code §66322. Parking exemptions, including transit, historic districts, existing space, permit districts, car share, and an ADU filed with a new home only when another exemption also applies.
• Gov. Code §66323. Mandatory ministerial units, the 800-square-foot detached cap, 4-foot yards, the 150-square-foot ingress expansion, multifamily counts, and sprinklers. Current text until AB 956 takes effect.
• Gov. Code §66325 and §66329. The article beats a conflicting ordinance, and a city may be less restrictive. The Coastal Act still applies.
• Gov. Code §§66333, 66334, and 66337. Junior ADU inside the residence, no added parking, and not a separate dwelling for a fire ordinance. Section links: 66334, 66337.
• Health and Safety Code §17958.1. An efficiency unit a city may allow, for no more than two persons, with at least 150 square feet.
• Public Resources Code §21064.3 and §21155. Major transit stop and high-quality transit corridor, used by section 66321 for the 18-foot floor.
• HCD ADU Handbook, March 2026 (PDF), from the handbook page. No parking and no front setback on 66323 units, the two-story reading, guest parking, the sprinkler example, and the fire-hazard-map note.
• AB 956, Chapter 791 (2026). Approved September 29, 2026. Two detached new single-family ADUs, still at 4-foot setbacks, an 800-square-foot cap, and the detached height floors. No required ministerial junior ADU once those two are built.
• SB 1117, Chapter 809 (2026). Approved September 29, 2026. Amends §66311.5 only. No change to setbacks, height, or parking.

Related pages: the legal guide, the planning guide, the glossary, the 2026 law update, and the city guides.