ADU rules in Maricopa County, AZ — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Arizona HB 2570 (2021) requires counties to allow ADUs on single-family lots. Maricopa County cannot ban ADUs, require owner-occupancy, or mandate additional parking. The county allows attached and detached ADUs with development standards including setbacks, lot coverage, and height limits. The updated 2026 zoning ordinance includes an 18-foot height cap for ADUs encroaching into setbacks and 30% side-yard coverage cap.
Under the updated Maricopa County Zoning Ordinance (effective January 2026), ADUs must comply with the zoning district's development standards for maximum yard coverage, lot coverage, building height, and minimum setbacks. There is currently no ADU-specific size limit apart from district standards. ADUs encroaching into setbacks are limited to one story/18 feet. The minimum ADU size under state law is 300 square feet.
Specific penalty amounts for this ordinance are not published in a publicly accessible fine schedule. Contact Maricopa County code enforcement directly for current fines, enforcement procedures, and hearing options.
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See how Maricopa County's adu rules rules stack up against other locations.
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