Rancho Cucamonga, CA Accessory Structures: ADU Rules (2026)

100, adopted by Ordinance No. 1049 on December 3, 2025, sets the citywide framework for ADUs and JADUs on any lot zoned for single-family or multi-family use. 050-1: an attached ADU has a 220-square-foot minimum and a maximum of 50 percent of the main dwelling's size or 1,200 square feet, whichever is less, capped at 25 feet in height; a detached ADU runs from a 350-square-foot minimum up to 1,200 square feet, capped at 16 feet, or 18 feet within a half mile of a major transit stop or high-quality transit corridor.

Setbacks are addressed in subsection (H): ADUs must maintain at least a four-foot setback from side and rear property lines and otherwise follow the underlying zone's front-yard standard, unless that standard would block an 800-square-foot, 16-foot-tall ADU built at the four-foot side/rear minimum, in which case the front standard is relaxed. No setback at all is required for an ADU built inside an existing structure or one rebuilt in the same footprint. 040 separately allows a Category 2 detached ADU of up to 800 square feet with only a four-foot side and rear setback regardless of the underlying zone's standard setback, and a Category 4 program permits up to eight detached ADUs on a lot with an existing multi-family building.

Parking under subsection (I) requires one space per newly built detached ADU unless the unit qualifies for one of several exemptions, including sitting within a half mile of transit. 030 gives the city 60 days to approve or deny a complete application.