Berkeley, CA Accessory Structures: ADU Rules (2026)

306 implements California Government Code Sections 66314 through 66339 locally. 306-1; multifamily lots may add up to 8 new-construction ADUs outside the Hillside Overlay, capped at the number of existing units, with at least one interior ADU required for up to 25 percent of existing units. 306-2 sets the development standards: maximum gross floor area is 1,200 square feet outside the Hillside Overlay, dropping to 850 square feet for a studio or one-bedroom and 1,000 square feet for two or more bedrooms inside it. New detached or attached construction outside the Hillside Overlay tops out at 25 feet in height; inside it, detached units are capped at 20 feet and attached units at 25 feet or the height limit of the existing building, whichever is lower.

Minimum lot line setbacks are 4 feet on the rear, interior side, and street side. ADUs are treated as an accessory use that does not count toward allowable density and are exempt from any local growth-control ordinance. Permit review runs through a Zoning Certificate rather than discretionary approval: the Zoning Officer must approve or deny within 60 days of a complete application, and a Zoning Certificate cannot be denied for an ADU that meets Government Code Section 66323 or for failing to correct an unrelated nonconforming zoning condition on the lot.