Brentwood's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Brentwood, California, there are 3 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

Brentwood must allow Accessory Dwelling Units on any single-family lot under California Government Code Section 65852.2, as expanded by AB 68, AB 881, and SB 13. Detached ADUs up to 800 sq ft with 4-foot setbacks are ministerial approvals processed within 60 days. AB 1033 now allows selling an ADU separately from the primary home.

Key details: Adu Up: ADU up to 800 sq ft allowed ministerially. 4-foot Side/rear: 4-foot side/rear setbacks, 16-ft height minimum. 60-day Approval: 60-day approval timeline required by state. No Impact: No impact fees under 750 sq ft. Ab 1033: AB 1033 enables separate ADU sale.

Contact your local code enforcement office for specific penalty information.

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

Shed Rules

Brentwood follows the California Building Code exemption allowing detached accessory structures under 120 square feet to be built without a building permit. Sheds must still comply with zoning setbacks, height limits, and HOA rules. Structures over 120 sq ft or with utilities require a building permit and Community Development review.

Key details: Permit/License: No building permit required under 120 sq ft. Measurement: Rear or side yard only, 3-5 ft setback typical. Measurement: Height limit generally 8-10 ft. Permit/License: Utilities or habitation trigger full permit. Fees: Cannot be used as a separate dwelling.

Contact your local code enforcement office for specific penalty information.

The rules around shed rules in Brentwood lean permissive, but that does not mean anything goes.

Garage Conversions

Brentwood garages must meet California Residential Code requirements for fire separation, including 5/8-inch Type X drywall on walls and ceilings separating the garage from living space and a self-closing, self-latching 20-minute fire-rated door. Conversion to an ADU is permitted by right under AB 68, and the city cannot require replacement parking for transit-adjacent conversions.

Key details: 5/8-in Type: 5/8-in Type X drywall separating garage from living space. 20-minute Fire-rated,: 20-minute fire-rated, self-closing door to house. Garage Floor: Garage floor must slope to door or drain. Conversion To: Conversion to ADU allowed ministerially. No Replacement: No replacement parking required near transit.

Contact your local code enforcement office for specific penalty information.

The Bottom Line

Compared to many U.S. cities, Brentwood gives residents more room on accessory structures. 2 of the 3 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

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.