Everything homeowners need to know about building an accessory dwelling unit in Concord - size limits, setbacks, permits, and the city's own rebate program that can help offset construction cost.
Last verified: August 2026
8/10 · Very ADU-friendly
1,200 sq ft
Max ADU size
16 ft*
Max height
Not required
Owner-occupancy
By-right
Permit type
This page summarizes Concord Municipal Code Chapter 18.200 (Accessory Dwelling Units) and California's statewide ADU law for general reference - it is not legal advice. Regulations change; always confirm current requirements with the City of Concord Planning Division before designing or applying for permits. See sources below.
Zoning & size requirements
What you're allowed to build
ADU type
Max size
Max height
Notes
Detached (new build or garage conversion)
1,200 sq ft
16 ft, up to 18 ft near a BART station or Clayton Road, or to match the primary home's roof pitch (up to 20 ft in some cases)
4 ft side and rear setback for new construction; conversions of existing legal structures generally don't need added setback
Attached (addition to the primary home)
1,200 sq ft or 50% of the primary dwelling's living area, whichever is smaller
Up to 25 ft, maximum 2 stories
Must meet the primary structure's setbacks
Junior ADU (JADU)
500 sq ft
Same as primary structure
Must be built within the walls of the existing house
Allowed zoning districts
Permitted in R-1, R-2, and R-3 residential districts, and generally in any zoning district where residential use is allowed, citywide. Confirm your parcel's zoning with the Planning Division before designing.
Additional standards
Setbacks, parking & other rules
Setbacks
4 ft from interior side and rear property lines for new construction; front and street-side setbacks follow the underlying zoning district unless the ADU is 800 sq ft or smaller and can't feasibly go elsewhere on the lot
Parking
1 off-street space, waived for garage/structure conversions, JADUs, and ADUs within a half-mile walk of transit
Units per lot
1 ADU plus 1 JADU on a single-family lot; existing multi-family properties may add a conversion ADU plus up to 2 detached units, or use California's newer multifamily allowance for up to 8 detached ADUs
Owner-occupancy
Not required for a standard ADU under state law. Concord's own code has required a recorded deed restriction for JADUs; under 2026's AB 1154, owner-occupancy can only be required when a JADU shares a bathroom with the main house - confirm current local practice with Planning
Rental terms
ADUs and JADUs may not be rented for fewer than 30 consecutive days - short-term rentals aren't permitted
Building code
Must meet current California Building, Residential, Energy, Plumbing, Mechanical, and Electrical Code standards
Ordinance history
How Concord's ADU rules got here
2017Statewide ADU law takes effect. California Government Code section 65852.2 required Concord, like every city in the state, to approve qualifying ADUs ministerially, without discretionary review.
2020State law overhaul forces local updates. A wave of state bills (AB 68, AB 881, AB 587, AB 2299, AB 671) cut minimum lot sizes, reduced setbacks, and eliminated parking requirements near transit, and Concord updated its own ordinance to match.
2023Housing element certified. On October 23, 2023, HCD found Concord's 2023-2031 Housing Element in substantial compliance with state law, while flagging continued implementation of the city's ADU program (Program 1) as an ongoing obligation.
2024Owner-occupancy requirement eliminated statewide. AB 976 permanently barred California cities, Concord included, from requiring owner-occupancy for standard ADUs.
2025ADU rebate program launches. Funded by a $277,226 California Housing Finance Agency grant, Concord began offering rebates of up to $15,000 toward ADU construction, plus free pre-approved building plans.
Worth knowing: Concord is one of relatively few Bay Area cities offering a direct cash rebate for ADU construction, on top of free pre-approved plans - a meaningful offset against the region's high build costs, though funding is limited and awarded first-come, first-served.
Permit process
How Concord ADU permitting works
1
Pre-application check
Confirm your lot's zoning and ADU eligibility with the Planning Division, (925) 671-3152 or zoning@cityofconcord.org, before you design.
2
Choose pre-approved or custom plans
Concord offers free, city pre-approved ADU plans with waived design and plan-check fees. Custom designs follow the standard building permit review process instead.
3
Prepare your submittal
You'll need a site plan, floor plans and elevations, and (for size calculations) floor plans of the existing house.
4
Submit for building permit review
State law requires a ministerial decision within 60 days of a complete application. Instructions to pay the application fee follow within about five business days of submittal.
5
Construction & inspections
Once permitted, schedule the standard framing, plumbing, electrical, and final inspections through the Building Division, (925) 671-3107.
6
Apply for the rebate (optional)
If you want the construction rebate, apply before September 30, 2026, get your building permit within 6 months of that application, and finish construction within 18 months of permit issuance.
Fees, timelines, and rebate availability are approximate and subject to change - confirm current figures with the Planning Division.
Budgeting
What it costs to build an ADU in Concord
Garage conversion
Roughly $70,000-$185,000, the least expensive path since the shell already exists
Basement/addition conversion
Roughly $100,000-$225,000, depending on existing structure and utility access
New detached ADU
Roughly $155,000-$350,000+, with Bay Area labor and material costs pushing many projects toward the higher end
Permit & plan check fees
Roughly $3,000-$10,000 for a custom design; largely waived on pre-approved plans aside from a site-plan review fee
City ADU rebate
Up to $15,000 for income-restricted units, or up to $7,500 for market-rate units, depending on size, while grant funding lasts
These are general ranges from local contractor estimates and regional reporting, not quotes - actual cost depends heavily on lot conditions, finishes, and design complexity. Using the city's free pre-approved plans is the most reliable way to control soft costs.
Before you apply
Tips for a smooth approval
Look at the pre-approved plans first. They skip most of the design and plan-check fees and review time that a custom project requires.
Check your height tier before finalizing a design. Standard detached ADUs cap out at 16 ft, but properties near BART or Clayton Road, or homes with a taller roof pitch, may qualify for 18-20 ft - worth confirming early.
Apply for the rebate before you break ground. The city's ADU rebate program requires an application before the permit process, not after - and funding is limited.
Plan rental terms around the 30-day minimum. Concord doesn't allow short-term rental of ADUs or JADUs, so design and finance the unit as a standard long-term rental.
Budget separately for utility hookups. Extending water, sewer, and electrical service to a detached unit is often one of the larger line items contractors quote separately from the structure itself.
FAQ
Common questions
Do I need to live on the property to build an ADU in Concord?
No, not for a standard ADU. California's AB 976 permanently eliminated owner-occupancy requirements for ADUs statewide as of 2024. A JADU may still require the owner to occupy the property in some cases - confirm current practice with the Planning Division.
How many ADUs can I build on one lot?
A single-family lot can add 1 ADU plus 1 JADU. Existing multi-family properties have more options, including a conversion ADU plus up to 2 detached units, or - under state law - up to 8 detached ADUs on qualifying multifamily sites.
Do I need parking for an ADU in Concord?
Usually one space is required, but it's waived for garage or structure conversions, JADUs, and any ADU within a half-mile walk of public transit.
How long does the permit process take?
State law requires a ministerial decision within 60 days of a complete application. Using the city's free pre-approved plans typically speeds things up further since design review is already done - confirm current timelines with the Planning Division.
What's the maximum size for a detached ADU in Concord?
Up to 1,200 sq ft, with a base height limit of 16 ft (up to 18-20 ft in certain locations or roof configurations).
How much does an ADU cost to build in Concord?
Garage conversions tend to run roughly $70,000-$185,000, basement or addition conversions $100,000-$225,000, and new detached units $155,000-$350,000 or more, based on local contractor estimates and regional reporting - before accounting for the city's rebate program.
Does Concord offer any financial help for building an ADU?
Yes. The city's ADU rebate program, funded by a California Housing Finance Agency grant, offers up to $15,000 for income-restricted units or up to $7,500 for market-rate units, plus free pre-approved building plans, subject to available funding and application deadlines.
Can I rent my ADU out on Airbnb or a short-term rental platform?
No. Concord requires ADU and JADU rentals to run at least 30 consecutive days, which rules out short-term and vacation rental use.
Has HCD found any problems with Concord's ADU rules?
Not that public records show as of this page's last verification. HCD's October 2023 review found Concord's housing element, which includes its ADU program, in substantial compliance with state law, and no separate ADU ordinance non-compliance finding for Concord turned up in HCD's published records. Still, confirm current requirements directly with the city, since local ordinances are periodically amended to track new state law.
