accessory dwelling units; requirements

HB 4028 requires Arizona municipalities with over 75,000 residents to allow accessory dwelling units (ADUs), or secondary housing units, on single-family lots. It mandates that municipalities permit at least one attached and one detached ADU per lot, with size limits (no larger than 75% of the main house or 1,000 sq ft), and prohibits restrictions on long-term rentals, tenant relationships, or extra parking. The bill sets a January 1, 2027 deadline for municipalities to adopt compliant regulations, after which ADUs would automatically be permitted without limits. The bill failed to pass in the legislature on February 23, 2026, and does not apply to tribal land, military airport areas, or high-noise airport zones.