Pasadena, CA Accessory Structures: ADU Rules (2026)

Municipal Code Section 17.50.275 governs both ADUs and Junior ADUs citywide. Under Section 17.50.275.B.1, ADUs are permitted by-right in every zoning district that allows single-family or multifamily residential use, on any lot with at least one existing or proposed dwelling. A single-family lot may add one detached new-construction ADU, one attached or detached conversion ADU, and one Junior ADU at the same time (Section 17.50.275.B.2.a.1). Size is scaled to unit type: the minimum ADU is 150 square feet (Section 17.50.275.D.1.a.(1)); an 'Exemption ADU' new-construction unit tops out at 800 square feet with four-foot side and rear setbacks; a non-exemption new-construction detached ADU can reach 1,200 square feet, while an attached new-construction ADU is capped at 850 square feet for a studio or one-bedroom and 1,000 square feet for anything larger (Section 17.50.275.D.1.a.(3)).

Height follows the same split: attached new-construction ADUs may rise to 25 feet and two stories, matching the underlying zone if that's lower, while detached new-construction ADUs are generally limited to 18 feet and two stories, dropping to 16 feet in Hillside Overlay Districts, Landmark or Historic Districts visible from the street, or for Exemption ADUs in the front-yard setback (Section 17.50.275.D.3.c). Non-exemption ADUs must keep at least six feet of building separation, eave to eave, from any other structure on the lot (Section 17.50.275.D.3.b).

Applications are reviewed ministerially, not through a public hearing: the Director must approve, conditionally approve, or deny the permit within the timelines set by Government Code Sections 66317, 66320, and 66335 (Section 17.50.275.A.2).