STATEWIDE UPDATE: New California ADU Bills SB13, AB68, AB881, AB670 have passed. These laws will create more options for building an ADU in Walnut Creek in 2020. To prepare for the upcoming changes use our ADU Services to learn how these laws will effect your property!
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Walnut Creek ADUs

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Last Updated 08/11/19


The city government of Walnut Creek has updated its local zoning codes to comply with the State ADU mandate.
The California Building Code (CBC) 2016 without amendments is adopted.
Relevant state bill updates for SB13, AB68, AB881, AB670 are shown in green below.


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:

One per primary dwelling.

AB68 & AB881 Update: Properties which convert existing space to create ADUs may be eligible for one ADU -AND- one JADU.

Types of ADUs allowed:

Attached, Detached & junior ADUs.

Lot size:

Lot coverage and other development standards of the zone apply, except for the standards outlined below.

AB68 & AB881 Update: Properties will not be subject to minimum lot standards by ordinance or of the applicable zoning district.

ADU size:

The maximum size for an ADU is 700 square feet of floor area. attached to the main unit cannot exceed 50 percent of the living area of the main unit.

AB68 & AB881 Update: Properties will be allowed up to 850 square feet for a one bedroom or up to 1,000 square feet for a two bedroom ADU.


New construction of an addition; Standard setbacks and Building Code apply except that no more than a 5-foot side is required for an ADU constructed above a detached garage, and at least a 10-foot SIDE setback is required for an ADU constructed above an accessory structure. Conversion of existing structure; Additional setbacks is not required for an ADU located within an existing building, except as mandated by the Building Code.

AB68 & AB881 Update: The maximum required setback for a detached new construction ADU shall be no more than 4 feet from the rear or side property lines.


One parking space will be required for the new construction of an ADU, in addition to the parking required for the main house. Parking can be provided on the lot as either a covered, uncovered and/or tandem space. No parking will be required for an ADU if it is located within one-half mile of a BART station or a public bus stop.

No additional parking is required for an ADU within an existing permitted building. If the ADU is located within a converted garage or carport which provides the required parking for the primary dwelling, the replacement parking may be provided on the lot with a covered, uncovered and/or tandem spaces.

AB68 & AB881 Update: Properties which convert an existing garage will not be subject to replacement parking requirements.

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.


Single family residential districts, no more than one dwelling unit on the parcel shall be rented or leased. A deed restriction attesting to this requirement must be recorded against the property.

SB13 Update: Owner-occupancy requirements for ADUs will be voided statewide for 5 years.

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: 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:

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

AB68 & AB881 Update: ADUs will be allowed statewide in all single-family or multi-family zoning districts.

Residential Building Code:

The California Building Code (CBC) 2016 without amendments 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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Read Walnut Creek Housing Market Update

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Customer since July, 2019

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Costs / ROI


* 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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