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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Walnut Creek 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 Walnut Creek has updated its local zoning codes to comply with the State ADU mandate.
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 permitted a total of 21 ADU project(s) in the past year of 2018, which makes it above average for ADU production compared to other cities statewide.


Number of ADUs allowed:

Under state law, each single-family home may now build at least one Accessory Dwelling Unit (ADU). Owner occupied single-family lots may build one Accessory Dwelling Unit (ADU) and one Junior ADU. Multi-family lots, per every four existing residential units, may build one Accessory Dwelling Unit (ADU), so long as the existing units were legally established.

As of January 1st, 2020

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are allowed. Accessory Dwelling Units may be new construction or converted from existing space. Junior Accessort Dwelling Unit (JADU)s must be converted from existing space.

Lot size:

ADU projects on single family or multi-family residential parcels will not be subject to the minimum lot size of the underlying local zoning code or by special ordinance. ~ AB68 & AB881 Update

As of January 1st, 2020

ADU size:

Residential lots will be permitted to construct up to 850 sq. ft. for a one bedroom ADU or up to 1,000 sq. ft. for a two bedroom ADU, regardless of the underlying zoning standards of the property. A Junior Accessory Dwelling Unit is permitted up to 500 sq. ft.. According to Califronia Residential Code, the minimum size of any living unit is 150 sq. ft. (including Accessory Dwelling Unit (ADU)s and Junior Accessory Dwelling Units). ~ AB-68

As of January 1st, 2020


Setbacks for a detached new construction Accessory Dwelling Unit shall be no more than 4 ft from the rear and side lot lines. No setbacks shall be required for Accessory Dwelling Units and Junior ADUs converted from legally eastablished existing space. Attached new construction Accessory Dwelling Units and conversions from existing space to be expanded must comply with the setbacks of the underlying zone. ~ According To AB68

As of January 1st, 2020


Replacement parking shall not apply to properties which convert an existing garage to an Accessory Dwelling Unit or Junior Accessory Dwelling Unit. ~ According To AB68

As of January 1st, 2020

Fire Safety:

Per state requirements.

Shape, materials and style:

ADUs must be designed to be architecturally consistent with the primary dwelling, including form, exterior siding and/or trim, roof materials and window placement and type. Any new entrances to an attached ADU must be located on the side or rear of the building.


Detached ADUs are limited to 1 story with a maximum height of 18 feet unless they are built over a garage or accessory structure, when standard height limits apply.

Design review:

ADU applications do not require a public hearing and are reviewed through the Building
Permit process. Some projects may also require a Site Development Permit or Tree Removal Permit. If an addition would trigger the Oversized Home Ordinance or Hillside Performance Standards, then an ADU is only permitted through the conversion of existing floor area.

Number of Bedrooms:

Not specified by State Standards.


Between between 2020 and 2025, owner occupancy requirements will not apply to new Accessory Dwelling Units. (applicable to new construction and conversion units) ~ According To SB13

As of January 1st, 2020

Utility connections:

New construction or additions; Local utilities may only impose a connection fee or capacity charge if it is proportionate to the burden of the proposed ADU upon the water or sewer system, based on either its size or the number of its plumbing fixtures. This fee or charge cannot exceed the reasonable cost of providing service. Contact the utility districts listed below for more information.

Conversions; Local utilities are prohibited from requiring a separate utility connection for the ADU or imposing a related connection fee or capacity charge. Contact the utility districts listed below for more information.

Permit Fees

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

Short term rentals

Short term rentals of 30 days or less require approval of a Conditional Use Permit (CUP).

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 allowed in all residential districts with a single family home on the lot with no more than one ADU permitted per lot.

As of January 1st, 2020

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

Walnut Creek City Planning Offices

Walnut Creek Planning & Zoning

1666 North Main Street Walnut Creek, CA 94596 Walnut Creek, CA 94596

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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: $4.42) * (ADU's Living Space: sqft)

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