Accessory Dwelling Unit (ADU) Guidelines

Are ADUs allowed in Concord:


Number of ADUs allowed:

One per primary residence.

Types of ADUs allowed:

Detached, attached and junior ADUs are all permitted.

Lot size:

Refer to State Requirements.

ADU size:

If the lot is less than 12,000 sq. ft. in net area, ADUs are limited to 150 sq. ft. to 640 sq. ft. For lots greater than 12,000 sq. ft. in net area, ADUs can be up to 1,200 sq. ft. An accessory dwelling unit constructed as an addition to an existing residence is limited to 50% of the existing floor area of the primary residence. Additionally, the floor area ratio for an attached ADU must not exceed 50% of the principal dwelling unit.


Depending on zoning districts, ADUs built as a new addition to an existing dwelling or as a newly constructed detached unit must setback a minimum of 15-20 feet from the rear and at least five feet from the side property line. Further information regarding setbacks can be found in the Residential Districts section of the Development Code. For accessory dwelling units proposed as a conversion of existing living space within a dwelling or through the conversion of an existing accessory structure (such as a detached garage), no additional setback is required. For second-story ADUs located above a garage or principal dwelling, a minimum of 5 feet from the side and rear property line is required.


A one bedroom unit requires one covered or uncovered space while a two bedroom unit must provide two spaces. This is in addition to the required off-street parking meant for the principal residence. The parking space (either uncovered or in tandem) can be located in the front yard setback if within an existing paved driveway. If a parking structure (garage or carport) for the primary dwelling unit is demolished as part of the construction of an ADU, the replacement spaces may be located in any configuration on the same lot as the accessory dwelling unit. However, additional parking spaces may not be required in certain situations. Consult the Compliance Checklist for exemptions.

Fire Safety:

Refer to State Requirements.

Shape, materials and style:

ADUs must be subordinate to the primary unit by size, location, and appearance, and should comply with the following guidelines: 1. Roofing and siding materials shall be the same style, color, and materials as the primary structure. 2. Color palettes should be the same color, or be complementary to, the color scheme of the primary structure. 3. Architectural detailing (fascia, window trim, and door trim) should match or complement the trim of the primary structure.


Must follow the underlying zoning code.

Design review:

New construction ADUs require Ministerial Approval and a building permit.

Number of Bedrooms:

ADUs up to 640 sq. ft. are limited to one bedroom while units between 640 sq. ft. to 1,200 sq. ft. can have up to two bedrooms.

Permit Fees:

Please refer to


“An accessory dwelling unit (ADU) is an independent dwelling located on the same lot as an existing single-family residence. The unit may be created by converting existing floor space, converting an existing accessory structure, attaching the unit to the main residence, or building a separate structure.” ADUs are allowed in Concord to provide residential development opportunitites of small rental housing units to meet the special needs of families and individuals.

Allowed Zones:

All single-family residential (RR, RS) districts, low-density residential districts (RL), and in other districts where a legal single family residences exists. ADUs shall meet all criteria of the district in which they are located. For more zoning information refer to

ADU Manual / Guide:

For further information about ADUs in Concord please visit

Potential Rental Income:

According to, an ADU in Corcord, CA can generate $18,000+ per year.

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