ADU rules in Monterey County, CA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Unincorporated Monterey County permits one ADU plus one JADU on lots with a single-family dwelling. Inland (Title 21, section 21.64.030) ADUs may not exceed 1,200 sq ft; JADUs max 500 sq ft. Detached ADUs default to a 16-ft height limit. State ADU law (Gov. Code 65852.2/66310+) preempts local rules where they conflict.
Monterey County regulates ADUs separately for the inland zone (Title 21, section 21.64.030) and the Coastal Zone (Title 20). Per the inland ordinance amending section 21.64.030, ADUs are limited to 1,200 square feet (section 21.06.372 defines an ADU as not exceeding 1,200 sq ft) and junior ADUs (JADUs) to 500 square feet. The county applies state standards in Government Code sections 65852.2 and 65852.22 (now also reorganized under Gov. Code 66310 et seq.), supplemented by local standards; where local rules conflict with state law, state law controls. A detached ADU is allowed up to 16 feet in height (or the district's accessory-structure height, whichever is greater); exceeding 16 ft requires a Use Permit. Side and rear setbacks are a minimum of 4 feet. The County ministerially approves qualifying ADUs/JADUs. Units on private wells or septic require Environmental Health review for adequate water and sewage. In the Coastal Zone, a November 18, 2025 ordinance (effective December 19, 2025) raised the coastal ADU size limit (reported up to 1,000 sq ft) and removed Big Sur's prior 50-unit cap, after California Coastal Commission approval.
ADUs built without required ministerial approval, Environmental Health clearance, or a building permit are subject to Monterey County code enforcement. ADUs may not be rented for 30 days or less (no vacation rental) and may not be sold separately from the primary dwelling.
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