Santa Ana, CA Accessory Structures: ADU Rules (2026)

2(A). Minimum unit size is 220 square feet for attached, detached, and junior units alike. Maximum size climbs to 1,000 square feet for attached and detached ADUs and 500 square feet for a JADU, though footnote (A) caps an attached ADU at 50 percent of the primary residence's habitable floor area unless the unit is 800 square feet or smaller, in which case the 50-percent cap doesn't apply. Detached ADUs also carry their own height ceiling: footnote (E) limits them to two stories or twenty feet in height, measured from the lowest adjacent grade to the highest point of the roof, while attached ADUs and JADUs may match the primary building's height.

Setbacks are uniform across unit types: 4 feet for side yard, street-side corner-lot setback, and rear yard, while front yard setback matches whatever the primary building's zoning district requires, though footnote (F) lets an ADU up to 800 square feet encroach into that front setback. Separation from the primary building must be at least 15 feet for detached ADUs, and lot coverage generally may not exceed what the underlying zoning district allows, subject to the same 800-square-foot exception. 2(B), not a discretionary design review.