Brentwood, CA Accessory Structures: ADU Rules (2026)

050(A) allows one ADU per lot with a proposed or existing single-family or multifamily dwelling, and one JADU per lot with no more than one single-family dwelling, unless a lot qualifies for the expanded "state exempt ADU" counts (up to two on a proposed multifamily lot, or the lesser of eight or the existing unit count on an existing multifamily lot). Height is tiered under subsection E: sixteen feet for a standard detached ADU, eighteen feet within a half-mile of a major transit stop, up to twenty feet to match the primary home's roof pitch, and twenty-five feet (or the underlying zone limit, whichever is lower) for an ADU attached to the house, capped at two stories.

Size is capped under subsection F at 850 square feet for a studio or one-bedroom unit and 1,000 square feet for two or more bedrooms, with an attached ADU further limited to 50% of the existing primary dwelling's floor area. Detached ADUs need at least four-foot side and rear setbacks and four feet of separation from any other building (subsections C and H). 040: the city must approve or deny within sixty days of a complete application (thirty days for preapproved plans), or the application is "deemed approved," with limited tolling for applicant-requested delays or bundled new-construction permits.

Parking is capped at one space per ADU with multiple exemptions (near transit, historic districts, conversions, car-share proximity) and no parking requirement at all for JADUs (subsection M). Impact fees are waived for ADUs under 750 square feet and for all JADUs (subsection J).