ADU Regulations in Concord, California

Zoning

Allowed ADU Types

State law requires cities to allow, on a single-family lot, one ADU converted from existing space, one JADU, and one new detached ADU of up to 800 sq ft. Multifamily lots can add up to 8 detached ADUs (not more than the number of existing units) plus conversions of non-livable space for up to 25% of existing units.

ADUs are permitted by right on all residential lots. Concord uses functional zone names (SFR = Single-Family Residential, LDR/MDR/HDR = Low/Medium/High Density Residential). The former Naval Weapons Station redevelopment area is planned for mixed-use development; ADU rules in that area will follow standard residential regulations once built out.

Source: City of Concord: Accessory Dwelling Units · Concord Municipal Code Section 18.200.180

Dimensions

Size & Setback Requirements

Setbacks

ADU size limit is the lesser of 50% of the main home or 1,000 sq ft on lots under 12,000 sq ft, or 1,200 sq ft on larger lots, but never below 800 sq ft. Minimum size is 150 sq ft. Concord's post-war tract neighborhoods offer consistently sized lots (typically 6,000–8,000 sq ft) that comfortably accommodate detached ADUs while meeting setback requirements. Neighborhoods near the Pleasant Hill/Contra Costa Centre BART station, which straddles the Concord/Pleasant Hill border, are particularly desirable for transit-oriented ADUs.

Permitting

Permit Process

Concord maintains a dedicated ADU webpage with submittal requirements and fee schedules. The city participates in Contra Costa County's countywide ADU resource program. Plan check is handled jointly by Planning and Building; inspections are managed by the Building Division. Concord Fire Department reviews fire/life-safety.

Infrastructure

Utilities & Requirements

Financials

ADU Costs in Concord

Concord's BART connectivity is its strongest ADU value driver. Units within a half-mile of the Concord or Pleasant Hill/Contra Costa Centre BART stations consistently command rents at the upper end of the range and experience minimal vacancy. Bay Area housing costs continue to push renters outward, sustaining strong demand in Contra Costa County.

State Law

California Rules That Apply in Concord

Concord can be more generous than state law but not stricter. These statewide minimums were last reviewed September 30, 2026.

Units per lot

Single-family lots can have one ADU converted from existing space, one JADU, and one new detached ADU (up to 800 sq ft). Multifamily lots can add up to 8 detached ADUs (never more than the number of existing units) plus conversions for up to 25% of existing units. Gov. Code §66323; SB 1211 (2024)

Size

Cities must allow at least an 800 sq ft ADU with 4 ft side and rear setbacks. Local maximums can be no lower than 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more bedrooms). JADUs are capped at 500 sq ft of interior livable space. Gov. Code §§66321, 66333

Height

Detached ADUs: at least 16 ft; 18 ft within half a mile of major transit (plus 2 ft to match the roof pitch of the main home) or on a lot with a multistory multifamily building. Attached ADUs: 25 ft or the zone height limit, whichever is lower. Gov. Code §66321(b)(4); AB 2221 and SB 897 (2022)

Setbacks

Side and rear setbacks for new ADUs can be no more than 4 ft. Conversions of existing legal structures need no extra setback. Front setbacks cannot block an 800 sq ft ADU. Gov. Code §66314(d)(7); AB 2221 (2022)

Permit timeline

The city has 15 business days to say whether an application is complete, or it is deemed complete. It must then approve or deny a complete application within 60 days, with no public hearing. Gov. Code §66317; SB 543 (2025)

Impact fees

No impact fees on ADUs under 750 sq ft; larger units pay fees proportional to the main home. ADUs and JADUs of 500 sq ft or less are exempt from school impact fees. Gov. Code §66324; SB 543 (2025)

Owner-occupancy

Cities cannot require the owner to live on site for an ADU. For a JADU, owner-occupancy can be required only if the JADU shares a bathroom with the main home. JADUs cannot be short-term rentals. AB 976 (2023); AB 1154 (2025)

Parking

No parking is required for an ADU within half a mile walk of public transit, in a historic district, or for a conversion, and garage parking lost to an ADU does not have to be replaced. Gov. Code §66322

Fire sprinklers

Sprinklers cannot be required in an ADU unless the main home is required to have them. Gov. Code §66314(d)(12)

Pre-approved plans

Every city must offer a program for pre-approved detached ADU plans, and plans matching a pre-approved design must be approved or denied within 30 days. AB 1332 (2023); Gov. Code §65852.27

Selling an ADU

Cities may choose to let owners sell an ADU separately as a condominium. It is a local opt-in, so check whether your city has adopted it. AB 1033 (2023)

Unpermitted ADUs

ADUs built without permits before 2020 can be legalized. Cities cannot deny them for code violations unless the unit is a health and safety hazard, and fees are limited. AB 2533 (2024)