Phoenix, AZ Accessory Structures: ADU Rules (2026)

Phoenix amended its Zoning Ordinance (Chapter 7, Section 706.A) effective with text amendment Z-TA-2-24-Y to comply with Arizona House Bill 2720, codified at A.R.S. Section 9-461.18, which requires municipalities over 75,000 people to allow at least one attached and one detached ADU as a permitted use on any single-family lot. A maximum of one attached ADU and one detached ADU are allowed per lot; a third detached ADU is permitted on lots one acre or larger when at least one ADU qualifies as affordable housing. A detached ADU may be located within a required rear or side yard, must be set back a minimum of 5 feet from a street side property line and 3 feet from an interior side or rear property line, with no setback required adjacent to a fully dedicated alley. Maximum height in a required yard is 15 feet unless a use permit is approved under Section 307. An ADU may not exceed 75 percent of the gross floor area of the primary dwelling, capped at 1,000 sq ft for lots up to 10,000 sq ft, or the lesser of 3,000 sq ft or 10 percent of net lot area for larger lots. State law bars the city from requiring additional parking, matching exterior design, or rear/side setbacks greater than 5 feet.