Building an ADU in Alameda, California

What you can build in Alameda

Alameda's ADU rules are in Section 30-5.18 of the Municipal Code. ADUs are allowed in any zone where residential use is allowed and the lot has an existing or proposed home. The city says ADUs "are allowed on both single-family and multi-family properties, subject to City regulations." Check your lot's zoning with the city's Citywide Viewer map.

Single-family lots: the current code allows "one (1) accessory dwelling unit and one (1) junior accessory dwelling unit." State law requires more. HCD says that on single-family lots, cities "must allow at least one ADU constructed from existing space, one JADU, and one newly constructed detached ADU." Alameda's own handout notes the one-ADU limit applies "Unless otherwise qualified for more under State law." The 2026 ordinance (below) lists one ADU inside the house or an existing accessory structure, one JADU and one detached ADU of up to 800 sq ft. Confirm your combination with the Planning Division.

Multifamily lots: the current code allows any number of ADUs inside portions of an existing building if each meets state building standards, plus two detached ADUs. State law allows up to eight detached ADUs on a lot with an existing multifamily building, not more than the number of existing units, and the 2026 ordinance would adopt that limit.

An ADU needs its own building permit, separate from any other work on the main house. The city says permit requests "that combine the ADU work with the primary residence work cannot be processed and will be rejected." For the statewide rules, see our California ADU guide. [1][2][4][5][7][8]

The 2026 ordinance update

The City Council held a public hearing on an updated ADU ordinance on September 15, 2026, and final passage was on the council's October 6, 2026 agenda (item 5-L). As of October 10, 2026, the council's online records did not yet show the outcome of that vote. The ordinance says it takes effect when 30 days have passed after final passage, so if it passed on October 6 it would take effect in early November 2026. The October 6 agenda item says the text was not changed when it was introduced. It would:

• list the state-mandated units for single-family lots: one ADU inside the house or an existing accessory structure, one detached ADU of up to 800 sq ft with 4-ft side and rear setbacks, and one JADU
• allow up to eight detached ADUs on a lot with an existing multifamily building, not more than the number of existing units, or two with a proposed multifamily building
• state that "No off-street parking is required for any accessory dwelling unit"
• add a 20-ft front setback for non-state-mandated ADUs, unless that would block a state-mandated unit
• make the city's ADU design standards recommendations instead of requirements
• remove owner occupancy from the JADU deed restriction (state law still requires it when the JADU shares a bathroom)
• measure ADU and JADU size as "interior livable space"
• allow an ADU to be sold separately as a condominium through a subdivision map (new Section 30-5.19)

Until the update takes effect, the code in force is the version last amended in 2022. Ask the Planning Division which version applies to your application. [2][5][6][8][9]

Size, height and setbacks

These limits are from the current code and the city's ADU handout.

• Size: no more than 1,200 sq ft. The code can't stop an ADU of at least 800 sq ft that is 16 ft tall with 4-ft side and rear setbacks.
• Detached height: 18 ft, or 20 ft when the ADU's roof pitch matches the main house. In a FEMA special flood hazard area, the ADU may be taller by the minimum needed to put the floor 1 ft above the base flood elevation, allow up to 8 ft of ceiling height and match the roof pitch.
• Attached height: 25 ft, or the zone's maximum building height if that is lower.
• Setbacks: 4 ft from side and rear lot lines for a new ADU. No setback is required for an existing accessory structure converted to an ADU, or one rebuilt in the same place and size (up to 18 ft tall). The front setback is the same as for the main house.
• Zero setbacks: a detached ADU can go right to the side and rear lot lines if it is at least 75 ft from the front lot line, the neighboring lot's adjoining area is not within 75 ft of that lot's front line, construction within 3 ft of the line is one-hour fire resistive, the ADU is no more than 16 ft tall, and it covers no more than 60% of the required rear yard (at least 600 sq ft allowed).
• Spacing and coverage: the current code requires 6 ft between a detached ADU and other buildings, which the Building Official may reduce with one-hour fire resistive construction. Total lot coverage of all buildings can't exceed 60%, except where that would block an 800 sq ft ADU up to 18 ft tall.
• Conversions: an ADU in an existing accessory structure may add up to 150 sq ft, only for getting in and out.

The handout and code also set design rules: an attached ADU must match the house's materials, colors and style, and its entrance can't be on a street-facing side. A detached ADU within 50 ft of a street must pick up the house's exterior features. The 2026 update would make these recommendations only. [2][4][5]

Parking

The city's ADU handout says: "No additional parking spaces required for an ADU." No replacement parking is needed when a garage, carport or covered parking structure is demolished or converted for an ADU.

If you keep the driveway and curb cut for parking, the driveway must be at least 18 ft long from the property line so a parked car doesn't stick into the street. Shorter driveways must be abandoned as part of the ADU project. [2][4]

Fees

City impact fees: Alameda's Master Fee Schedule (effective July 2025) lists the citywide development impact fee for an "Accessory Dwelling Unit or Accessory Dwelling Unit-Junior" as $0, compared with $17,340 for a new single-family home. The code also exempts ADUs from the city's Improvement Tax.

Other city fees: building plan check and permit fees still apply. If you need a Certificate of Approval to demolish an accessory building (for example, a pre-1942 garage) along with your ADU application, the fee schedule lists "Certificate of Approval with ADU - Demo of Accessory Building Concurrent with an ADU Application" at $1,169.37 in total. The city's planning page links a planning fee calculator for estimates.

School fees: under state law, school districts may charge fees on ADUs larger than 500 sq ft of interior livable space.

Utilities: the city's handout says new or separate utility connections may be required and recommends contacting the utilities early: PG&E (gas), Alameda Municipal Power (electric) and East Bay MUD (water and sewer). The code says an ADU is not a new residential use for city connection fees or capacity charges. Under state law, ADUs converted from existing space and JADUs are not a new residential use for connection fees unless built with a new single-family home. See our ADU cost guide. [2][3][4][8][10]

How long it takes

The code says an ADU application "shall be reviewed ministerially within sixty (60) days from receipt of a completed application without discretionary review or public hearing." State law also requires the city to tell you within 15 business days whether your application is complete.

The city's ADU application instructions say plan review "may be completed within 30 days" if the first submittal meets all codes, and "Each round of review is a 30 day turnaround." No neighbor notice is required. Some related work can add time: a pre-1942 garage needs a Certificate of Approval before demolition, and second-story additions or other non-exempt changes to the main house need Design Review. The city allows the ministerial Design Review and the ADU building permit to be reviewed at the same time. See our ADU permit process guide. [2][4][8][11]

Junior ADUs and garage conversions

A JADU is up to 500 sq ft and must be inside a single-family home, which can include an attached garage. It needs an efficiency kitchen with a cooking appliance, a food preparation counter and storage cabinets, plus its own exterior entrance that isn't on a street-facing side. It may share a bathroom with the house. No additional parking is required.

Before the building permit is issued, you record a Declaration of Restrictions with the Alameda County Recorder. It bars selling the JADU separately from the house and requires rentals longer than 30 days.

Owner occupancy: the current code and the city's January 2025 handout require the owner to live in the house or the JADU. Since January 1, 2026, state law requires owner occupancy only when the JADU shares a bathroom with the house, and the 2026 ordinance removes it from the city's JADU restriction. If your JADU has its own bathroom, confirm with the Planning Division whether the owner-occupancy covenant still applies.

Garage conversions: converting an existing garage or accessory structure needs no setbacks, and you may add up to 150 sq ft for getting in and out. A converted garage must replace the garage door with wall material, color and trim matching the existing building. See our junior ADU guide and garage conversion guide. [2][4][5][8][11]

Renting it out

Alameda requires ADU and JADU rentals to be "for a period longer than thirty (30) days," so short-term rentals are not allowed. An ADU can't be sold separately from the main house except as state law allows.

Rentals are also covered by Alameda's rent program. The city's fee schedule describes "permitted accessory dwelling units on the same lot as a single-family home" as Partially Regulated Units, which are subject to Ordinance 3250 except for the limits on annual rent increases. [2][3][4]

Pre-approved ADU plans

Alameda preapproves detached ADU plans submitted by designers, architects and builders. The city says applications using them get a faster review and "a reduced application fee." Construction and inspection fees still apply. You must contract with the plan's designer, and every plan still needs site-specific plans, studies and engineering. The first plan listed is Alameda Tiny Homes, a 500 sq ft, single-story, one-bedroom detached ADU. See the Preapproved ADUs page. [4][12]

Permit steps in Alameda

1. Check your lot and the rules

   Look up your zoning on the city's Citywide Viewer map, read the city's ADU handout, and call the Zoning Line at 510-747-6805 with questions. [1][4][7]

2. Clear any demolition first

   For a pre-1942 garage or structure, get a Certificate of Approval from the Planning Division, then a separate demolition permit. Newer structures need only a demolition permit. [4][11]

3. Get Design Review if the main house changes

   Work on the main house such as a second-story addition or raising the house may need Design Review; it can be reviewed at the same time as the ADU permit. [4]

4. Apply online for the ADU building permit

   Submit a building permit pre-application on the Accela Citizen Access portal with your plans and the ADU Zoning Checklist. Keep the ADU on its own permit, separate from other work. Apply for solar, panel upgrade, new meter and encroachment permits at the same time if needed. [1][4][11]

5. Record the JADU restriction

   For a junior ADU, record a notarized Declaration of Restrictions at the Alameda County Recorder's Office before the permit is issued. [4][11]

6. Respond to review and get your permit

   Planning checks zoning and Building checks code. The city sends a Hold Notice if corrections are needed or when the permit is ready. [11]

7. Build, inspect and get your Certificate of Occupancy

   Call for inspections at (510) 747-6830. After the final inspection you receive a Certificate of Occupancy. [4][7]

Pre-approved and sample plans

• Alameda Preapproved ADU Plans

  Designer-owned detached ADU plans preapproved by the city, with faster review and a reduced application fee. [12]

Who to call

• Alameda Planning Division (Zoning Line)

  ADU zoning questions

  510-747-6805

  [1]

• City of Alameda Permit Center

  Building permits; open Monday-Thursday, closed Fridays

  (510) 747-6800

  2263 Santa Clara Ave. Rm 190, Alameda, CA 94501

  [7]

• Alameda Building Inspections

  Schedule an inspection

  (510) 747-6830

  [7]

Questions people ask