Phoenix, AZ Accessory Structures: ADU Rules (2026)
ADU rules in Phoenix, AZ, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADUs per lot
- 2 (1 attached + 1 detached); 3rd on 1-acre affordable lots
- Detached ADU setback
- 5 ft street side / 3 ft interior side or rear
- Max height in required yard
- 15 ft (use permit for more)
- Max size
- 75% of primary dwelling, max 1,000 sq ft (small lots)
- Code Section
- Zoning Ordinance Sec. 706.A; A.R.S. 9-461.18
Summary
Phoenix permits up to two accessory dwelling units (one attached, one detached) on a single-family detached lot, with a third allowed on lots of one acre or more when one ADU is affordable housing. A detached ADU may sit as close as 5 feet from a street side property line and 3 feet from an interior side or rear line under Zoning Ordinance Section 706.A.
A. Accessory Dwelling Units (ADU). 1. In zoning districts where accessory dwelling units are a permitted use, this section applies to accessory dwelling units when a lot having no more than one single-family dwelling unit is permitted one or more ADUs per the underlying zoning district. 2. An ADU may be either attached to or detached from the primary dwelling unit, subject to the following: a. A maximum of one attached ADU may be provided per lot. b. A maximum of one detached ADU may be connected to the primary dwelling unit by a porch, deck, covered patio, carport, breezeway, or similar. 4. A detached ADU may be located within the required rear or side yard(s), and/or within a required on-lot perimeter setback which is not also the front yard. Setbacks. (1) Minimum five feet from a street side property line. (2) Minimum three feet from an interior side or rear property line. (3) No setback is required adjacent to a fully dedicated alley. (4) Front setbacks apply as stated for the zoning district. Permitted Height. When located within the required rear or side yards: maximum 15 feet, unless use permit approval for a greater height is obtained per Section 307.
Full Breakdown
S. 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.
Violations & Fines
Constructing an ADU without required permits or outside the Section 706.A standards is a zoning and building-code violation enforced by the Planning and Development Department and Neighborhood Services. The city may issue a stop-work order or notice of violation and require correction; uncorrected violations can lead to civil code-enforcement action under the Phoenix City Code.
Frequently Asked Questions
How many ADUs can I build in Phoenix?
How close to the property line can a detached ADU be?
How big can an ADU be?
Sources & Official References
Other rules in Phoenix
How Phoenix compares: Easiest Cities to Build an ADU·Compare Phoenix to another location·View the Arizona accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Maricopa County handle adu rules.