Arcadia Zoning and ADU Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Arcadia’s Development Code sets ADU and junior ADU rules in section 9102.01.080, with Planning reviewing ADU applications at (626) 574-5423 and a pre-approved ADU program available to homeowners. This guide summarizes the size, height, setback and parking rules in the city’s ADU standards document, how review works and what to do with an older garage conversion.

The city has amended its code more than once, so confirm current numbers with Planning before you design or sell.

Arcadia ADUs at a glance

Code section	Arcadia Development Code section 9102.01.080, Accessory Dwelling Units
Units on a single-family lot	One ADU and one junior ADU, plus a limited detached new-construction ADU
Junior ADU	Up to 500 square feet; owner occupancy required
Detached new-construction ADU	800 square feet or smaller; 4-foot side and rear setbacks
Detached height	16 feet; up to 18 feet near major transit; up to 20 feet to match the main roof pitch
Parking	One space generally required, with listed exceptions such as within half a mile of transit
Rental term	No ADU or JADU may be rented for less than 28 days
Review	Ministerial; approve or deny within 60 days of a complete application
Planning phone	(626) 574-5423

Size, height and setbacks

The city’s ADU standards document breaks the rules down by type of unit.

Size

A junior ADU can be no more than 500 square feet. A detached, new-construction ADU on a single-family lot is 800 square feet or smaller.

Units permitted under subsection F can be 850 square feet for a studio or one-bedroom and 1,000 square feet for two or more bedrooms, and an attached ADU is limited to 50 percent of the floor area of the existing primary dwelling.

The document says size limits, floor area ratio, front setback, lot coverage or open space rules cannot require an ADU smaller than 800 square feet.

Height

A detached ADU may not exceed 16 feet, or 18 feet on a lot within one-half mile walking distance of a major transit stop or high quality transit corridor, with up to two more feet (a 20 foot maximum) if needed to match the main roof pitch. An attached ADU may not exceed 25 feet or the zone’s limit, whichever is lower, and may not exceed two stories.

Setbacks

A converted ADU or JADU needs side and rear setbacks sufficient for fire and safety. A new detached ADU on a single-family lot needs at least four feet on the sides and rear. No setback is required if the ADU is built in the same location and to the same dimensions as an existing structure.

Parking, owner occupancy and rentals

The standards generally require one off-street space per ADU, which can be in a setback or tandem.

They list exceptions, including lots within half a mile walking distance of public transit, historic districts, conversions of existing space, areas where on-street permits are required but not offered to the ADU occupant, and lots within one block of a car share stop.

If a garage or carport is demolished or converted for an ADU, the replacement spaces are not required. ADUs created on or after January 1, 2020 carry no owner-occupancy requirement, but JADUs do. No ADU or JADU may be rented for fewer than 28 days.

Review, fees and fire rules

ADU applications are approved without a discretionary hearing, and the city must approve or deny a complete application within 60 days. The document says the ADU permit processing fee is set by council resolution.

No impact fee applies to an ADU under 750 square feet, and larger ones are charged in proportion to the main home’s size. A converted ADU on a single-family lot does not need a new utility connection, while other ADUs generally do.

Fire sprinklers are required in the ADU if they are required in the primary residence, but building an ADU does not trigger sprinklers in the existing house.

The city’s Development Code also says a lot may hold no more than two detached accessory structures, counting ADUs, so a shed and a detached ADU may already use up the allowance.

Pre-approved plans and the permit step

Arcadia has a Pre-Approved Accessory Dwelling Unit program page. It says all pre-approved plans still require a site plan, and it points to a submittal checklist for using a pre-approved plan. After Planning clears the project, the building permit follows the process in our Arcadia building permits guide.

Garage conversions and older units

The city’s ADU document covers conversions, and it says converted units must still comply with local building code requirements. A garage turned into living space years ago without a permit is a common find in older neighborhoods. A buyer or lender will ask for the permit record, and unpermitted space may not count toward the appraisal. Our Arcadia code enforcement guide explains how Code Services handles complaints.

State ADU law and Arcadia

California’s ADU statute, Government Code section 66314 and following, sets a floor that every city must follow, and local ordinances fill in the details.

The state requires ministerial review within 60 days of a complete application, bars a city from requiring more than a limited set of standards, and generally allows an ADU or conversion inside existing space without added setbacks.

The California Department of Housing and Community Development (HCD) publishes a handbook and keeps a list of the state requirements. Because state law changes often, treat the city’s current ordinance and handout as the final word on size, height, parking and fees for your lot.

ADUs, garage conversions and selling an Arcadia house

Many older homes have a converted garage or a backyard unit built without permits. Buyers and lenders ask about them, and California sellers generally disclose known unpermitted work. Our guide to selling as-is with unpermitted work explains the rules, and our Prop 13 guide explains how new construction can affect property tax. Before you list:

• Check city records for permits on any ADU, conversion or addition.
• Ask Planning whether the structure could qualify under current rules.
• Estimate plans, fees and corrections needed to legalize it.
• Compare that with selling as-is and letting a cash buyer take on the legalization.

Questions to ask Planning before you design

• Does my lot and zone allow an ADU, a junior ADU, or both?
• Is a pre-approved or pre-reviewed ADU plan available?
• What are the current impact, utility and school fees for the size I am considering?
• Can my existing garage or accessory structure be converted without changing its footprint?
• Are there fire, slope, easement or utility constraints on my lot?

Junior ADUs and garage conversions in more detail

State law treats a junior ADU as a unit of up to 500 square feet created inside the walls of an existing or proposed single-family home, with an efficiency kitchen and a recorded restriction that keeps it from being sold apart from the house.

A garage conversion is a different path: the unit replaces the garage, and state law generally does not require the city to demand replacement parking. Both are common sources of unpermitted space in older Arcadia neighborhoods, which is why buyers’ agents and appraisers ask for the permit record.

If a conversion was done without a permit, the usual fix is to submit as-built drawings, pay the fees and pass inspection, which can take months and cost real money.

Fees, utilities and property tax

State law limits the impact fees a city can charge on smaller ADUs and on conversions of existing space, and it limits when a separate utility connection can be required.

Larger new units can still carry impact fees, school fees and water or sewer connection charges, so ask for an itemized estimate before you commit to plans. New construction is generally reassessed for property tax under Prop 13, which means an ADU can raise the bill for the whole property. Our Prop 13 guide explains how reassessment works.

Why ADUs matter for resale

A permitted ADU can add rental income and appeal for some buyers, but an unpermitted one can complicate financing and appraisal. Lenders typically want permitted living area, and an appraiser may not count unpermitted space.

Because an ADU generally cannot be sold separately from the main home, its value comes through the sale of the whole property.

If you inherited a house with an old backyard unit, or bought one with a converted garage, check what the city has on file before you decide how to sell. Our probate home sale guide covers inherited property.

How to sell a house in Arcadia

1. Ask the city for the permit record on any ADU or conversion.
2. Collect plans, inspection records and any city notices.
3. Request a no-obligation cash offer for the house as it stands.
4. Choose your closing date.
5. Close with no repairs, legalization or showings required.

See also our Arcadia page and the Los Angeles County hub.

Frequently asked questions

What is the maximum size of a junior ADU in Arcadia?

The city’s ADU standards say a junior ADU can be no more than 500 square feet.

What setbacks apply to a detached ADU in Arcadia?

A new detached ADU on a single-family lot needs side and rear setbacks of at least four feet. A conversion needs setbacks sufficient for fire and safety.

Does an Arcadia ADU need parking?

Generally one off-street space, with exceptions such as lots within half a mile walking distance of public transit, and parking removed for a garage conversion need not be replaced.

How long does the city have to review an ADU application?

Per the city’s standards, it must approve or deny a complete application within 60 days.

Can I rent my ADU short term?

The city’s standards say no ADU or JADU may be rented for fewer than 28 days.

Can I sell my Arcadia house with an unpermitted ADU or garage conversion?

Yes. You can disclose it and sell as-is, including to a cash buyer. Our statewide guide explains the disclosure rules.

More guides

• We Buy Houses in Arcadia
• We Buy Houses in Los Angeles County
• Los Angeles County Property Tax Guide
• Arcadia Building Permits Guide
• Arcadia Code Enforcement Guide
• All California Guides

Sources

• City of Arcadia: Accessory Dwelling Units
• City of Arcadia: Accessory Dwelling Unit standards (Development Code)
• City of Arcadia: Pre-Approved ADU Programs
• City of Arcadia: Building Services

This guide is general information from public sources, not legal advice. Confirm current rules, fees and hours with the city.