Brentwood's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Brentwood, California, there are 4 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

ADU Rules

Chapter 17.715 lets one ADU and one JADU onto qualifying lots in the RE, R-1-E, R-1, R-2, R-3, COR, CR and PEC zones. Detached ADUs cap at 16 feet high (up to 20 near transit), size runs 850 to 1,000 square feet, and applications are approved ministerially within 60 days with no hearing.

Key details: Eligible zones: RE, R-1-E, R-1, R-2, R-3, COR, CR, PEC. Detached ADU height: 16 ft (up to 20 ft near transit). Max ADU size: 850 sf studio/1BR, 1,000 sf 2+BR. Review timeline: 60 days, ministerial, no hearing. Parking requirement: 1 space/ADU max, several exemptions.

An ADU or JADU built without permits before January 1, 2020 can often be legalized under § 17.715.050(G)(2) unless the chief building official finds correction of a violation necessary under Health and Safety Code § 17920.3; through 2030, owners facing a correction notice may request a five-year delay in enforcement under subsection G(4). Building or occupying an ADU with no permit at all, outside that legalization path, exposes the owner to the code's general misdemeanor/infraction enforcement under § 1.20.010.

Shed & Carport Rules

Brentwood limits a portable shed in a rear or side yard to 120 square feet of floor area and a height no greater than the adjacent fence, up to 7 feet. Sheds cannot sit in the front yard, must leave a 3-foot gated path to the rear yard, and cannot block windows or exits. Larger accessory buildings top out at 15 feet and one story, and California Building Code permits apply.

Key details: Max shed height: 7 feet (matches adjacent fence). Max shed floor area: 120 square feet. Accessory building height cap: One story, 15 feet. Rear yard coverage cap: 50% of required rear yard. Permit: Building permit required per CBC.

Violations of the accessory-structure standards are enforced like any other Brentwood Municipal Code offense under Section 1.20.010: a first infraction draws a fine up to $100, a second within twelve months up to $200, and a third or later up to $500, with each day the oversized shed or unpermitted structure remains counted as a separate violation. The city attorney can instead charge repeat violations as a misdemeanor, punishable by up to $1,000 and six months in jail.

ADU Impact Fees

Brentwood charges development impact fees on accessory dwelling units through its adopted development fee program, but waives them for any ADU under 750 square feet and for junior ADUs entirely. Larger ADUs pay fees prorated to the primary dwelling's square footage. The fee excludes water and sewer connection or capacity charges, which are billed separately under the ADU chapter's utility rules.

Key details: Small ADU exemption: Under 750 sq ft: no impact fee. JADUs: Always exempt from impact fees. Larger ADUs: Fee prorated to primary home size. Utility fees: Billed separately, not in impact fee. Citation: BMC § 17.715.050(J).

Impact fees are collected before a building permit is issued for the ADU or JADU; the community development department will not issue permits until the applicable fee, calculated under the city's adopted fee resolution, is paid. Because the ADU chapter is part of Title 17, a permit issued in violation of this section is void under Brentwood Municipal Code § 17.890.004, and knowing violations of Title 17 are infractions punishable by a fine of up to $250 per day under § 17.890.007.

ADU Owner Occupancy

Brentwood requires the property owner to live on-site when a junior accessory dwelling unit is added, occupying either the main house or the JADU itself, but the same chapter imposes no owner-occupancy requirement on standalone ADUs. Government agencies, land trusts and housing organizations are exempt from the JADU rule.

Key details: JADU owner occupancy: Required: owner in house or JADU. Standalone ADU: No owner-occupancy requirement. Exempt owners: Government agency, land trust, housing org. Enforcement tool: Recorded deed restriction, BMC § 17.715.050(I). Citation: BMC § 17.715.050(L).

Occupying neither the primary dwelling nor the JADU as required violates the recorded deed restriction under § 17.715.050(I)(2) as well as § 17.715.050(L); the city can pursue this as a Title 17 infraction under § 17.890.007, punishable by a fine of up to $250 for each day the violation continues, and a false owner-occupancy deed restriction can also expose the owner to civil enforcement by the city as beneficiary of the recorded instrument.

If you are coming from a city with tighter rules, you will find Brentwood gives residents more flexibility on adu owner occupancy.

The Bottom Line

Brentwood's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Brentwood is broadly strict or permissive.

Keep in mind that Brentwood can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.