Statewide Update: New California ADU Bills AB68, SB13, AB881, AB670 have passed. These laws create more options for building an ADU in 2020. Use ADU Services to learn how they affect your property!

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Union City ADUs

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PLANNING OFFICE The city planning office is not open to the public at this time, but is accepting ADU permit questions and applications.

The city government of Union City will approve ADUs under California's statewide mandated regulations.
The California Building Code (CBC) 2019 is adopted.
Relevant state bill updates for SB13, AB68, AB881, AB670 are shown in green below.

Last Updated 03/27/20


City Hint: The city has not yet responded to requests for ADU permit volumes for the past year, but they will be provided here once response has been received.


Number of ADUs allowed:

According to state law, all single-family homes are allowed at least one Accessory Dwelling Unit (ADU). Additionally, single-family lots which are owner-occupied may create one Accessory Dwelling Unit (ADU) and one Junior ADU. Also, multi-family lots may now add one ADU per every four existing residential units, so long as they were legally established.

As of January 1st, 2020

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are permitted. ADUs may be new construction or converted from existing space. JADUs must be converted from existing space.

Lot size:

Residential properties will not be subject to any minimum lot size for ADUs by ordinance or of the underlying zoning district. ~ AB68

As of January 1st, 2020

ADU size:

Residential properties will be approved to build up to 850 sqft for a one bed ADU or up to 1,000 sqft for a two bed ADU, regardless of the underlying zoning standards of the property. A Junior Accessort Dwelling Unit (JADU) is approved up to 500 sqft. According to Califronia Residential Code, the minimum size of any living unit is 150 sqft (including Accessory Dwelling Unit (ADU)s and Junior Accessort Dwelling Unit (JADU)s). ~ Updated: State Law AB-68

As of January 1st, 2020


The maximum required setback for a detached new construction Accessory Dwelling Unit shall be no more than 4 ft from the rear and side property lines. Setbacks will not be required for Accessory Dwelling Units and Junior Accessort Dwelling Unit (JADU)s converted from existing space that was legally eastablished. Attached Accessory Dwelling Units and conversions from existing space to be expanded will be required to comply with the setbacks of the underlying zone. ~ Updated: State Law AB-68

As of January 1st, 2020


Replacement parking shall not apply to parcels which convert an existing garage to an Accessory Dwelling Unit (ADU) or JADU. ~ AB68

As of January 1st, 2020

Fire Safety:

Per state minimum requirements.

Shape, materials and style:

Accessory units must be clearly subordinate to the main house in terms of size, location and appearance.
 The exterior appearance and character of the accessory unit shall reflect that of the main house.
 Outside stairways must meet setback standards and shall not be visible from the public street.
 If a manufactured home is proposed as an accessory unit, it must be identical to the main house in terms of siding and roof materials, roof pitch, roof eaves and color.


Detached accessory units are limited to one story unless the ADU will be added over a garage consistent with state law.

Design review:

 Attached accessory unit: A building permit is required if the accessory unit is proposed to be attached to the main house, located on the ground floor, and complies with all applicable requirements. Administrative Site Development Review approval by the Planning Division is required prior to building permit issuance if the accessory unit is proposed as a second-story addition or as part of a new principal dwelling.
 Detached accessory unit: Administrative Site Development Review approval by the Planning Division is required prior to building permit issuance if the accessory unit is proposed as a detached structure.

Number of Bedrooms:

Not specified by State Standards.


Owner-occupancy will not be required for new Accessory Dwelling Units (conversion and new construction) built between 2020 and 2025. ~ SB-13

As of January 1st, 2020

Utility connections:

Adequate water and sewer service must be available to support the ADU. Separate or combined utilities are allowed.

Permit Fees

SB13 Update: As of January 1st, 2020, local impact fees for ADUs will be reduced substantially statewide.

Allowed Zones:

*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***

ADUs are permitted on single family lots with one dwelling and multi-family lots with one dwelling. Modular/manufactured units are allowed, as long as they meet all City requirements (Planning and Building).

As of January 1st, 2020

Kitchen / Bath:

Accessory units must include a complete independent living facility for sleeping, cooking, and sanitation purposes. A kitchen and bathroom must be permitted for the sole use of the unit.

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

Union City City Planning Offices

Union City Planning Department

34009 Alvarado-Niles Road Union City, CA 94587 Union City, CA 94587

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Kerry Worden

American Mortgage Management

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Union City ADU Marketplace

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* upon completion of ADU


* based on local average price per sqft


* estimated by location


* 30 years / 5% interest rate / 20% down payment


Appreciation Estimate = (Base Value: $) / (Home's Living Space: sqft) * (ADU's Living Space: sqft)

Rental Estimate = (Rent Per Sqft: $3.68) * (ADU's Living Space: sqft)

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