Downey Zoning and ADU Guide for Homeowners and Sellers

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team. Information comes from City of Downey ADU and Planning pages; sources are listed at the end.

Downey publishes ADU standards, fact sheets by property type and a planning contact, and the city says it updated its ADU and junior ADU rules in June 2026. Check current requirements with the city before you build, legalize or sell a unit.

Downey ADU resources at a glance

What rules apply to an ADU in Downey?

The city points homeowners to Municipal Code Section 9414 for the standards that apply when planning and designing an ADU. Because the city changed its rules in 2026, do not rely on older summaries. Ask the Planning Division which version applies to your lot.

Does Downey have pre-approved ADU plans?

The city has a program for pre-approved detached ADU plans under Assembly Bill 1332, but its page states that as of July 28, 2026 no pre-approved plans were available. The city is inviting design professionals to submit plans to join the program.

Even when plans are posted, they are only about 80% complete and always need site-specific changes, and the designer keeps the copyright, so you would contract with the designer directly. Check the page before assuming a stock plan is ready to use.

How an ADU or garage conversion affects selling a house in Downey

A permitted ADU can be a selling point. An unpermitted one is a problem buyers’ lenders and inspectors notice. In California, sellers generally must disclose known unpermitted work. On a traditional listing, you can try to permit the unit, remove it, price it in, or offer a credit. All take time.

How to sell a Downey house with an unpermitted ADU

1. Check the city’s records. Ask Building and Safety what is permitted at the address.
2. Gather what you have. Plans, receipts, inspection cards.
3. Compare options. Legalize, remove, or sell as-is.
4. Disclose honestly. A cash offer does not change disclosure duties but removes repair steps.

We buy Downey houses as they are. See selling as-is in Downey, our Downey building permits guide and code enforcement guide.

Questions about a unit on your property? Call (424) 435-2326 or request a cash offer. There is no cost and no obligation.

Downey single-family ADU standards from the city’s fact sheet

The Planning Division publishes a fact sheet for the R-1 single-family zone. It is an overview, not a replacement for the ordinance, and the city says other regulations may apply to a specific project.

Because the city also reports changing its ADU rules in 2026, treat the numbers below as what the fact sheet showed when we read it and confirm them with Planning at (562) 904-7154 or planning@downeyca.org before you design or buy.

Other fact-sheet requirements include a separate exterior entrance, new mechanical equipment at least 5 feet from side and rear property lines, and permanent washer and dryer connections for units over 500 sq ft. For ADUs over 800 sq ft the sheet adds design rules: a street-facing front entrance for new construction, exterior materials, colors and roof slope that match the main home, and obscured or frosted glass in second-story windows and doors.

A JADU needs at least an efficiency kitchen, access to a shared restroom through an interior door if it has no bathroom of its own, and a deed restriction requiring owner occupancy in one of the units.

How to submit ADU plans in Downey

1. Read the fact sheet for your property type. The city has separate sheets for single-family and multi-family lots.
2. Register for Accela Citizen Access. All ADU plans must be submitted electronically through the city’s portal, and you can track review status there.
3. Prepare the digital package. The city’s handouts explain orientation, scale and upload instructions, and the Building and Safety forms page has submittal checklists.
4. Plan for fire review. The Fire Department’s ADU Fire Plan Guide covers fire department access, sprinkler and hydrant requirements, egress and emergency escape, and smoke alarms.
5. Ask about the address. For the pre-approved program, the city says to submit a new address request at plan submittal to avoid delays.

What an unpermitted ADU or garage conversion means for a Downey sale

If a previous owner turned a garage, patio or storage room into a unit without permits, the unit may not meet the setbacks, parking, egress or fire requirements above. A buyer’s lender may treat the space as unfinished, and an appraiser may leave it out of the value.

Under California Civil Code section 1102.1, an as-is sale does not waive the transfer disclosure statement, and your duty to disclose material facts stays in place.

If you know about an unpermitted conversion, raise it with your agent or escrow officer early, because section 1102.3 lets a buyer cancel within three days of in-person delivery, or five days of mailing, when a disclosure arrives after an offer.

Options include permitting the unit, which means meeting the standards above; restoring the space to its original use; pricing the house with the condition in mind; or selling to a cash buyer who takes it as it stands. See the Downey building permits guide for how the city handles permit records.

Downey zoning and ADU FAQ

Which Downey code section covers ADUs?

The city’s ADU page cites Downey Municipal Code Section 9414.

Did Downey change its ADU rules recently?

The city says it updated its ADU and JADU rules in June 2026. Confirm details with the Planning Division at (562) 904-7154.

Can I sell a Downey house with an unpermitted ADU?

Yes. It must be disclosed, but a cash buyer can purchase the property as it is.

How many ADUs can a single-family lot have in Downey?

The city’s R-1 fact sheet lists one JADU converted from existing space plus up to two ADUs, one new construction and one conversion of existing space. Confirm with Planning, since the city says its rules changed in 2026.

What is a JADU in Downey?

The city’s fact sheet describes a junior ADU as a unit of no more than 500 square feet contained entirely within a single-family residence, with at least an efficiency kitchen.

Does Downey require parking for an ADU?

The fact sheet calls for one uncovered space per ADU, with exemptions including within half a mile walking distance of public transit. No parking is required for a JADU, and no replacement parking is required when a garage is converted.

Are pre-approved ADU plans available in Downey?

The city’s page said that as of July 28, 2026 it had no pre-approved plans available and was inviting design professionals to submit plans for the program.

Sources

• City of Downey: ADU Information & Resources
• City of Downey: Pre-Approved Standard Plans for Detached ADUs
• City of Downey: Planning

This guide is general information, not legal advice. Zoning rules change; confirm with the City of Downey.