Westminster, CA Accessory Structures: ADU Rules (2026)

The City of Westminster adopted its permanent ADU regulations as Ordinance No. 2572 on March 24, 2021, codified at Westminster Municipal Code Section 17.400.135 (Residential Uses—Accessory Dwelling Units). An ADU is an attached or detached unit with complete independent living facilities—living, sleeping, cooking, and sanitation—on a parcel with an existing dwelling, and may be created by new construction, an addition, conversion of existing space, or conversion of an existing garage or accessory structure. Properties zoned for single-family or multifamily use may be eligible. Per the city's ADU page, a single-family lot may add one ADU plus, if owner-occupied, one Junior ADU. Review is ministerial through the combined Planning Zoning Clearance and Building Division plan check, with Engineering review where applicable. Notably, in a March 3, 2023 review letter the California Department of Housing and Community Development (HCD) found Westminster's adopted ordinance partly noncompliant with state law (Gov. Code 65852.2): the city's 16-foot ADU height cap (Section 4.17.400.135.B.4) is below the 16/18/25-foot minimums state law guarantees, and the ordinance's zone list and JADU-zone language were more restrictive than state law allows. State ADU law (Gov. Code 66310 et seq./65852.2) overrides any stricter local provision, so applicants should rely on the state minimums where the city ordinance is more restrictive.