The statewide rules that govern every San Gabriel Valley ADU: sizes, setbacks, approval timelines, fees, and the 2024 to 2026 bills, with each answer cited to the California Government Code.
Statewide ADU Law
California preempts most local ADU rules. A city must approve a code-compliant ADU ministerially, within set timelines, at sizes and setbacks the state fixes. Your city sets only a narrow band of objective standards on top. Below is the statewide floor, verified against the Government Code. Your city's page covers what it adds locally.
This page summarizes California ADU law for general information and is not legal advice. Confirm specifics with your city and the state's source before you build.
The Statewide Floor
No local ordinance can go below these. They apply in Pasadena, Arcadia, El Monte, and every other San Gabriel Valley city.
Approval is ministerial, with no public hearing and no CEQA review. A city can layer objective standards on top, but it cannot drop below this floor.
The Basics
Short answer: An ADU is a full independent home with its own kitchen and bath. A JADU is up to 500 sq ft carved from inside the existing house and can share a bath.
An accessory dwelling unit is an independent living space with its own kitchen, bathroom, and sleeping area. It can be detached, attached to the main home, or converted from existing space like a garage. A junior ADU is smaller and more limited. It must sit within the walls of an existing single-family home, cannot exceed 500 square feet, may share a bathroom with the main house, and requires only an efficiency kitchen.
Short answer: One ADU plus one JADU on a single-family lot, by right.
On a lot with one single-family home, state law guarantees one ADU, either detached or attached, plus one junior ADU inside the house. A city must allow that combination and cannot require a minimum lot size to do it. Lots with existing multifamily buildings follow different, higher counts, covered in the multifamily section below.
Dimensions
Short answer: Every city must allow at least 800 sq ft. Detached units commonly go to 1,200 sq ft; attached is capped at 50% of the main home.
A city has to permit a detached ADU of at least 800 square feet no matter what its local rules say. Most cities set their own ceiling at 1,000 or 1,200 square feet for detached units. An attached ADU is limited to 50 percent of the primary home's floor area, and a junior ADU stays at 500 square feet. A city cannot apply a lot-coverage, floor-area-ratio, or open-space rule that would block at least an 800-square-foot unit.
Short answer: 4 feet from side and rear lot lines. No setback at all for an ADU built inside an existing structure.
State law caps side and rear setbacks at 4 feet for a new detached ADU. A city cannot require more. When an ADU is created inside an existing structure, or rebuilt in the same footprint as a former garage, no setback can be required at all. There is no state-mandated front setback specific to ADUs, so the underlying zone's front setback applies.
Short answer: At least 16 ft for a detached unit, 18 ft near transit or on a multifamily lot, and up to 25 ft or the main home's height for an attached ADU.
A city must allow a detached ADU to reach at least 16 feet. That floor rises to 18 feet if the lot is within half a mile of a major transit stop or has an existing multifamily building, and an extra two feet are allowed to match the primary home's roof pitch. An ADU attached to the main house can rise to 25 feet or the height the zone allows for the primary dwelling, whichever is lower.
Short answer: No minimum lot size, no owner-occupancy mandate, no replacement parking for a garage conversion, and no standard that physically prevents an 800 sq ft unit.
A city cannot impose a minimum lot size, require the owner to live on site, or demand replacement parking when a garage is converted into an ADU. It cannot apply lot-coverage, floor-area, or open-space limits that would make at least an 800-square-foot ADU impossible. And it cannot require correction of unrelated, non-safety code issues on the main house as a condition of approving the ADU.
Process
Short answer: Yes. A code-compliant ADU is approved over the counter, with no hearing and no discretionary review.
State law requires cities to act on an ADU permit ministerially. That means staff check the application against objective standards and approve it if it complies. There is no public hearing, no design board, and no neighbor notice or appeal process. Discretionary review is not allowed for a code-compliant ADU.
Short answer: 60 days from a complete application. Miss the deadline and the permit is deemed approved.
A city has 60 days to approve or deny a complete ADU application. If the application is submitted with the main home, the ADU clock can run with that project's timeline. When a city fails to act within 60 days, the ADU is considered approved by operation of law. The clock only runs once the application is complete, so a city can pause it by issuing a timely, specific list of what is missing.
Short answer: No. Ministerial ADU approvals are exempt from CEQA.
Because an ADU permit is ministerial rather than discretionary, it is not a project subject to the California Environmental Quality Act. A city cannot require an environmental study or use CEQA as grounds to delay or deny a compliant ADU. This is one reason the 60-day clock can hold.
Short answer: Since Jan 1, 2025, every city must run a pre-approved plan program and review a permit using one within 30 days.
AB 1332 took effect January 1, 2025. It requires each city to create a program for pre-approved ADU plans and to accept owner-submitted plans for that program. When a homeowner applies using a pre-approved plan, the city must approve or deny within 30 days rather than 60. Picking a standard, pre-reviewed design is one of the fastest paths to a permit.
Short answer: Only objective standards. No subjective design review, and standards cannot effectively block the unit.
A city may apply objective design standards, the kind that can be measured the same way by any reviewer, such as matching roof pitch, siding material, or window trim to the main home. It cannot use subjective design review, taste-based judgments, or standards so strict they physically prevent a code-compliant ADU. If a project meets the objective standards, approval is mandatory.
Short answer: No. The San Gabriel Valley is inland, so coastal-zone ADU rules do not apply here.
AB 462 and related coastal provisions deal with how ADU law interacts with the Coastal Act in cities inside the coastal zone. Every San Gabriel Valley city, from Pasadena to Diamond Bar, sits well inland of the coastal zone, so a coastal development permit is not part of the ADU process here. The standard statewide rules on this page govern instead.
Costs
Short answer: At most one space per ADU, and none at all in many common cases, including within half a mile of transit.
A city can require no more than one off-street parking space per ADU, and that space can be on a driveway or in tandem. No parking can be required at all when the ADU is within half a mile walking distance of a major transit stop, is part of the existing home, is in a historic district, is a converted garage, or is where on-street permits are required but not offered to the unit. When a garage is converted, the city cannot make you replace the lost covered parking.
Short answer: No impact fees under 750 sq ft. At 750 sq ft and up, fees must be proportional to the main home's size.
Development impact fees cannot be charged on any ADU smaller than 750 square feet. For an ADU of 750 square feet or more, any impact fee has to be charged proportionally to the square footage of the primary dwelling, so a small ADU pays a small fraction. JADUs, which top out at 500 square feet, never trigger impact fees.
Short answer: School districts may charge developer fees on new conditioned floor area, priced per square foot.
School developer fees are separate from city impact fees and are not waived by ADU law. A school district may levy its Level 1 fee on the new conditioned square footage an ADU adds, charged at a per-square-foot rate the district sets. A garage or interior conversion that adds little or no new conditioned area usually owes little or nothing.
Short answer: No new connection or capacity fee for an interior or JADU conversion. For a new detached unit, any fee must be proportional to its size.
For an ADU created within an existing home or for a junior ADU, a city or special district cannot require a new or separate utility connection or charge a related connection or capacity fee. For a new detached ADU, a separate connection may be required, but any connection or capacity charge must be proportionate to the ADU's size or its burden on the system, not a flat full-home fee.
Short answer: Only if the property is on a septic system. Homes on the public sewer cannot be forced into a septic study.
When a home uses a private septic system, the city may require a percolation test or proof the system can handle the added unit before approving an ADU. Almost every San Gabriel Valley property is on the public sewer, where no septic test applies. The rule exists for the small number of lots still on septic, mostly in foothill or unincorporated pockets.
Living & Selling
Short answer: No owner-occupancy rule for ADUs, permanently. A JADU still requires the owner to live on the property.
As of AB 976, cities are permanently barred from requiring the owner to live on the property as a condition of permitting an ADU. You can build an ADU and rent out both it and the main house. Junior ADUs are the exception: because a JADU shares the single-family structure, the owner must occupy either the main home or the JADU.
Short answer: Yes, but not as a short-term rental. Rentals must be 30 days or longer.
An ADU can be rented out, which is what makes it a financing tool. State law lets cities prohibit rentals shorter than 30 days, and most do, so an ADU generally cannot be used as a nightly or weekly vacation rental. A standard month-to-month or annual lease is fine. The ADU cannot be sold separately from the main home unless the city has opted into AB 1033, covered next.
Short answer: Only if the city has opted in to AB 1033. Many cities, including most in the SGV, have not yet.
AB 1033 lets a city choose to allow an ADU to be sold separately from the main house as a condominium. It is local-option, not automatic. A homeowner can sell an ADU on its own title only in a city that has formally adopted AB 1033. As of 2026 most San Gabriel Valley cities have not opted in, so in those cities the ADU stays part of the primary property.
Short answer: Create a condominium plan, notify and get consent from any existing lienholder, and record the condo map.
In an opted-in city, separating an ADU means establishing a condominium under the Davis-Stirling Act, which sets up an association and shared-maintenance terms. Any lender with an existing mortgage on the property must be notified and must consent before the units can be split, since it changes the collateral. The condominium plan is then recorded with the county. This is why financing matters early: the existing loan has a say.
Short answer: A JADU requires a recorded deed restriction on size and owner-occupancy. AB 1033 requires a recorded condominium plan.
Before a junior ADU is finalized, the owner records a deed restriction noting the 500-square-foot limit, the prohibition on separate sale, and the owner-occupancy requirement. It runs with the land and binds future owners. For a separate ADU sale under AB 1033, the parallel recorded document is the condominium plan that legally divides the property. Standard detached and attached ADUs that are not being sold separately do not need a deed restriction.
Other Lots
Short answer: Convert unused space into multiple ADUs (at least one, up to 25% of existing units) plus up to eight detached units.
On a lot with an existing multifamily building, state law allows conversions of non-livable space such as storage rooms, boiler rooms, or hallways into ADUs, at least one and up to 25 percent of the existing unit count. Separately, SB 1211 allows up to eight detached ADUs on the lot, as long as the total does not exceed the number of existing units. These counts are far higher than the one-plus-one allowed on single-family lots.
Short answer: Only if the main house is required to have them. An ADU cannot be held to a higher sprinkler standard than the primary home.
A city cannot require fire sprinklers in an ADU unless they are also required in the primary dwelling. If the existing home was built without sprinklers and is not being required to add them, the ADU does not need them either. Newer homes built under codes that mandate sprinklers will carry that requirement into a new ADU.
Short answer: No outright ban. Under AB 670, HOA rules that prohibit ADUs on single-family lots are void; only reasonable standards are allowed.
AB 670 makes any HOA covenant that effectively bars an ADU or JADU on a single-family lot unenforceable. An association can still apply reasonable restrictions, such as design guidelines, that do not unreasonably increase cost or effectively prohibit the unit. So a homeowners association cannot say no, though it may have a say on objective design within those limits.
Who Decides
Short answer: The state fixes the floor: size, height, setbacks, parking, fees, and timelines. Cities set only objective standards on top, like materials and exact fee schedules.
The state controls the things that decide whether you can build at all: the guaranteed 800-square-foot size, 16-foot height, 4-foot setbacks, the one-space parking cap and its exemptions, the impact-fee and utility rules, and the ministerial 60-day timeline. A city's discretion is limited to objective standards layered on top, such as matching exterior materials, its own published permit fee schedule, and which optional programs like AB 1033 it adopts. When local rules conflict with the state floor, the state floor wins.
2024 to 2026
The bills that changed the rules most recently, in the order they took effect.
Removes the sunset on the rule barring cities from requiring owners to live on site. Owner-occupancy can no longer be a condition of permitting an ADU, permanently.
Lets a city opt in to allow an ADU to be sold separately as a condominium. Where adopted, it opens a path to sell the unit on its own title.
Every city must run a pre-approved ADU plan program and review a permit that uses one within 30 days, half the standard clock.
Raises the cap to up to eight detached ADUs on a lot with an existing multifamily building and bars cities from requiring replacement parking when covered spaces are removed.
Expands the path to legalize ADUs and JADUs built before 2020, blocking cities from denying a permit over code rules that did not apply when the unit was built, unless there is a safety issue.
Get Started
You have the statewide rules. Tell us about your home and your project, and we will come back with the loan options that fit.
