Duarte Zoning and ADU Guide for Homeowners

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

Duarte regulates accessory dwelling units under Duarte Development Code Chapter 19.60.160, takes preliminary ADU plans by email at Planning@CityofDuarte.ca.gov, and runs a Pre-Approved ADU Program, though the state housing department has flagged parts of the ordinance as inconsistent with state law. This guide explains the size, height and parking rules the city publishes, how its two application paths work, why the city’s page and current state law may not match, and what to do if your home has an older garage conversion or unpermitted unit.

Duarte ADUs at a glance

Ordinance	Duarte Development Code (Title 19), Chapter 19.60.160
Junior ADU size	150 to 500 square feet
Detached ADU	Up to 1,000 square feet
Attached ADU	Up to 50% of the primary dwelling, or the greater of 850 sq ft (one bedroom or less) or 1,000 sq ft (two or more bedrooms)
Conversion ADU	No size limit when created entirely within the footprint of an existing structure
Height	18 feet plus 2 feet for matching roof pitch; two stories maximum, unless built on top of a detached garage
Parking	One off-street space per ADU; none within one-half mile walking distance of public transit
Preliminary review	About 10 business days for an assigned planner

What the city publishes

The city’s ADU page, a quick guide to city and state requirements, gives these figures. A junior ADU is between 150 and 500 square feet. A detached ADU can be up to 1,000 square feet.

An attached ADU can be up to 50 percent of the existing primary dwelling, or the greater of 850 square feet for one bedroom or less and 1,000 square feet for two bedrooms or more.

A conversion ADU created entirely within the footprint of an existing structure has no size limit, though the page says a converted structure can expand by no more than 150 square feet to accommodate ingress or egress, and no more than 50 cubic yards can be excavated.

Height is capped at 18 feet plus 2 feet for matching roof pitch, with a maximum of two stories unless the unit is built on top of a detached garage. The page requires one off-street parking space for each ADU, but none for ADUs within one-half mile walking distance of public transit.

It says owner occupancy applies to junior ADUs with shared sanitation facilities. It does not publish setbacks, fee amounts or a rental term.

Two ways to apply

Standard review

Email preliminary plans to Planning@CityofDuarte.ca.gov. An assigned planner reviews them for about 10 business days, then issues comments, attaches the master application and invoices fees. Once the invoice is paid, the planner reviews revised plans, and the cycle repeats until corrections are resolved.

The Planning Division then issues an approval letter, and you submit a full set of construction plans to Building & Safety in person at the Community Development counter.

Pre-Approved ADU Program

The city offers standard plans already reviewed and approved by Building & Safety. You contact Planning to see whether the plans fit your lot, buy the plan from the selected designer, who helps prepare a site-specific layout, complete the applications and email them to Planning. The page says modifications and customizations are not permitted.

State law and the city page

On March 17, 2026, the California Department of Housing and Community Development (HCD) issued a letter reviewing Duarte’s ADU ordinance, Ordinance No. 916, adopted April 25, 2023, under state ADU law.

The letter identifies several provisions it says conflict with state law, including sections of 19.60.160 on deed restrictions, separate sale, owner occupancy, size, height, floor area ratio, architecture, visibility, fire sprinklers, parking and local development standards.

State law takes precedence over a conflicting local rule, so the figures on the city’s page may not be the final word. Ask Planning which standards it is applying to your lot today, and get the answer in writing.

As general state law, ADUs are also entitled to setbacks of no more than four feet on the side and rear, which the city page does not list. Confirm the current figure with Planning.

State ADU law and Duarte

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 a Duarte 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 Duarte 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 Duarte

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 Duarte page, the Duarte as-is sale page, the Duarte cash offer process and the Los Angeles County hub.

Frequently asked questions

What ADU sizes does Duarte allow?

Per the city’s page: junior ADUs 150 to 500 square feet, detached ADUs up to 1,000 square feet, and attached ADUs up to 50% of the primary dwelling or the greater of 850 or 1,000 square feet depending on bedrooms.

How do I start an ADU application in Duarte?

Email preliminary plans to Planning@CityofDuarte.ca.gov. A planner reviews them for about 10 business days. The city also has a Pre-Approved ADU Program.

Does Duarte require parking for an ADU?

The city’s page requires one off-street space per ADU, but none within one-half mile walking distance of public transit.

Has the state questioned Duarte’s ADU ordinance?

Yes. HCD sent a review letter dated March 17, 2026 flagging provisions of Ordinance No. 916 it says conflict with state law. Ask Planning which standards apply to your lot.

Can I convert my garage to an ADU in Duarte?

The city’s page lists conversion ADUs within an existing footprint with no size limit. Garage conversions are also on the code enforcement list (D.M.C. 19.38), so get a permit.

Can I sell my Duarte 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 Duarte
• We Buy Houses in Los Angeles County
• Los Angeles County Property Tax Guide
• Duarte Building Permits Guide
• Duarte Code Enforcement Guide
• Sell a Duarte House As-Is
• Duarte Cash Offer Process
• Azusa Building Permits Guide
• All California Guides

Sources

• City of Duarte: Accessory Dwelling Units
• California HCD: Review of Duarte’s ADU Ordinance (March 17, 2026)
• City of Duarte: Municipal Code Enforcement

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