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Concord, California: ADU Regulations

Date Updated:



ADUs in single- and multi-family residential (including R, NTS, CO, CMX, NC, DP, and DMX). Junior ADUs in single-family only (including R, NTS, CO, and CMX).

Types of ADUs allowed:

Attached (Large and Small), Detached (Large and Small), Conversion, Junior.

Lot size:


ADU size:

Junior ADU – 500 sq.ft.
Studio/One Bedroom – 850 sq.ft.
Two Bedroom – 1,000 sq.ft.
Attached ADUs shall not exceed 50% of the existing living area of the principal dwelling.

Lot coverage:







Junior ADUs require an efficiency kitchen.


Attached and detached ADUs shall provide independent sanitation facilities.
Junior ADUs may include separate sanitation facilities or share them with the existing residence.


One off-street parking space is required per ADU, unless (a) the ADU is located within one-half mile radius of public transit, (b) the ADU is located within an architecturally significant historic district, (c) the ADU is a conversion and located within the existing walls of the principal dwelling or an existing legal accessory building, (d) when on-street parking permits are required but not offered to the occupant of the ADU, (e) when there is a car share vehicle site located within one block of the ADU.


Side and Rear: 4’
Corner side yard: 4’ (ADU cannot be closer to the property line than the proposed/existing primary residence)

Note: The minimum setbacks shall be waived for an ADU constructed entirely within the footprint of a legally constructed principal residence or accessory building, and for up to 150 sq.ft. outside of the footprint of said principal residence or accessory building if the additional area is limited to accommodating ingress and egress; however, the ADU must still comply with all applicable Building Code Regulations.


Detached: 16'.
Attached: commensurate with primary residence


Must be subordinate to primary residence

Rear Yard Coverage:

Must comply with underlying zoning regulations.


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.

Note: Historic Neighborhoods or Districts should be assessed on a project by project basis.

Source Code: (Note that as of December 2020 the municipal code does not have the most current ADU regulations)

Important Note: Rules and regulations are updated and changed frequently. It’s one of our jobs to be up to speed and navigate those regulations. Let us know if our website isn’t up to date or if you have any information that could help. Cheers!