Lancaster, CA Accessory Structures: ADU Rules (2026)

Municipal Code Sec. A governs ADUs on single-family lots, limiting each legal parcel to one ADU and one JADU. An attached ADU (new construction joined to the primary structure) cannot exceed 850 square feet for a studio or one-bedroom unit, or 1,200 square feet for a unit with two or more bedrooms, and cannot exceed 25 feet in height or two stories; front setbacks run 25 feet, side and rear setbacks 4 feet each, though the code guarantees the front-setback and lot-coverage rules alone cannot shrink an ADU below 850 square feet.

A detached ADU carries the same size caps but a lower height ceiling of 18 feet, extendable to 20 feet to match a roof pitch aligned with the primary dwelling, using the same 25-foot front and 4-foot side/rear setbacks. 5, RR-1, SRR, R-15000 and R-10,000; 50% in R-7,000, MDR and HDR; and 60% in mixed-use zones. On multi-family lots, Sec. B allows interior ADUs converted from up to 25% of existing units (minimum one) plus up to two detached ADUs per lot, with detached units following the same 850/1,200 square-foot caps, 18-to-20-foot height limit and 25-foot front, 4-foot side/rear setback pattern. Interior (converted-space) ADUs must instead maintain independent exterior access and side/rear setbacks adequate for fire and life safety under Sec. 2.