Imperial County, CA Accessory Structures: ADU Rules (2026)

ADUs in unincorporated Imperial County are governed by Title 9, Division 4, Chapter 5 of the Land Use Code (Sections beginning 90405). The local code permits one ADU on lots zoned for single-family (R-1) or multifamily (R-2) use that contain an existing single-family dwelling, limits detached ADU floor area to 1,200 square feet, requires no setback for an existing garage converted to an ADU, and allows a maximum five-foot side and rear setback for an ADU built above a garage (Section 90405.03). A junior ADU (JADU) is capped at 500 square feet within an existing single-family structure and carries an owner-occupancy requirement under Section 90405.11. However, in its June 26, 2025 findings letter the California Department of Housing and Community Development (HCD) determined the county code does not fully comply with State ADU Law (Gov. Code 66310-66342). HCD specifically flagged outdated citations to repealed Government Code 65852.2, an over-restrictive parking standard (the county required up to two spaces; state law caps it at one space per ADU under Gov. Code 66314(d)(10)(A)), the subjective 'compatible' design standard, and missing allowances for up to eight detached ADUs on lots with existing multifamily dwellings under Gov. Code 66323. Where the county rule is stricter than state law, state law preempts it.