Check your property's zoning, browse designs & get contractor estimates for your ADU project:
Last Updated 10/13/20
City Hint: The city permitted a total of 13 ADU projects in the past year of 2019, which is below the average compared to other cities in California.
Number of ADUs allowed:
1. Lots with a single family dwelling:
Either one (1) attached accessory dwelling unit constructed at the same time as a new single family dwelling; one (1) attached accessory dwelling unit located within the footprint of an existing single family dwelling, plus up to 150 square feet of additional floor area if limited to accommodating ingress and egress; or one (1) detached accessory dwelling unit located within the footprint of an existing accessory structure, plus up to 150 square feet of additional floor area if limited to accommodating ingress and egress; and
ii. One (1) detached accessory dwelling unit;
2. Lots with an existing multiple family dwelling:
i. Multiple attached accessory dwelling units on a lot containing a multiple family dwelling, not to exceed twenty-five (25) percent of the number of existing dwelling units contained within multiple family dwellings; and
ii. Two (2) detached accessory dwelling units
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.
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
ADU floor area is based on the Size of the lot:
14,999 square feet or less: 850 square feet for one bedroom, 1,000 square feet for a two bedroom
15,000 to 19,999 square feet: 900 square feet for one bedroom, 1,000 square feet for a two bedroom
20,000 square feet or more: 950 square feet for one bedroom, 1,000 square feet for a two bedroom
Attached accessory dwelling units shall not exceed fifty percent (50%) of the gross floor area of the main building, or a gross floor area of 800 square feet, whichever is more, when the main building is already in existence
The maximum gross floor area for a junior accessory dwelling unit shall be 500 square feet.
No greater than a four (4) foot side or rear setback shall be required for an accessory dwelling unit constructed beyond the footprint of an existing building, unless the portion constructed beyond the footprint of an existing building does not exceed 150 square feet and is limited to accommodating ingress and egress
The minimum setbacks and courts shall be waived for an accessory dwelling unit constructed entirely within the footprint of an existing building, and for up to 150 square feet outside of the footprint of an existing building if the additional area is limited to accommodating ingress and egress; however, the accessory dwelling unit must still comply with all applicable provisions of Title 9.
No parking spaces are required
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.
The maximum building height shall be waived in the amount necessary to accommodate an accessory dwelling unit with a building height of up to sixteen (16) feet.
The accessory dwelling unit shall be designed to be architecturally consistent with the main building, including building form, exterior siding and/or trim, roof form and materials, and window placement/type. Any new entrances to an attached accessory dwelling unit shall be located on the side or in the rear of the building.
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
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.
Short term rentals
Short term rentals of 30 days or less require approval of a Conditional Use Permit (CUP).
*** 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.
Residential Building Code:
The California Building Code (CBC) 2019 is adopted.
Walnut Creek Planning & Zoning
1666 North Main Street Walnut Creek, CA 94596 Walnut Creek, CA 94596
ADU Design Library
Browse hundreds of models to find the right fit for your property.
ADU Model 850 sqft
W 25 ft L 17 ft
ADU Model 480 sqft
W 30 ft L 16 ft
ADU Model 300 sqft
W 25 ft L 12 ft
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SELECT ADU SIZE & TYPE
* upon completion of ADU
CONSTRUCTION COST ESTIMATE
* based on local average price per sqft
SELECT ADU SIZE & TYPE
Size: 500 sqft
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)