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Zoning Guide

ADU Rules in Phoenix, Arizona

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ADU Rules in Phoenix, Arizona

Arizona's casita statute is HB 2720 (2024), codified at A.R.S. §9-461.18, applying to cities with 75,000+ population. HB 2673 is unrelated.

Arizona's casita statute is HB 2720 (2024), codified at A.R.S. §9-461.18, applying to cities with 75,000+ population. HB 2673 is unrelated.

Arizona's casita statute is HB 2720 (2024), codified at A.R.S. §9-461.18, applying to cities with 75,000+ population. HB 2673 is unrelated.

Permitted ADU Types

  • Detached ADU: A standalone structure on the residential lot
  • Attached ADU: An addition to the primary home with its own entrance
  • Garage Conversion: Converting an existing garage to a dwelling unit
  • Internal ADU: Converting space within the existing home

Size Limits

ADU Type Maximum Size
Detached ADU 1,000 sq ft or 50% of primary dwelling
Attached ADU 1,000 sq ft or 50% of primary dwelling
Garage Conversion Existing footprint

Setbacks

  • Front: Must meet base zone standard (typically 20–25 ft)
  • Side: 5 feet minimum
  • Rear: 5–10 feet minimum depending on zone
  • From primary dwelling: No minimum separation required in many zones

Height

  • Detached ADU: Maximum 14 feet for flat lots; up to 20 feet on sloped lots in some zones
  • Cannot exceed height of primary dwelling

Parking

One additional off-street parking space is required per ADU in most Phoenix zones. In some transit-served areas, parking requirements may be waived.

Heat Island and Desert Climate

Phoenix's extreme heat (summer temperatures exceeding 115°F) affects ADU design:

  • Cool roof materials and adequate insulation are important
  • Shade structures are beneficial
  • Water-efficient landscaping required
  • Proper HVAC design for extreme heat is essential

Permit Process

  1. Check zoning: Verify your zone at phoenix.gov/pdd
  2. Design: Prepare architectural plans meeting Phoenix standards
  3. Submit: Apply online through Phoenix's permitting portal
  4. Plan review: Zoning and building code review
  5. Permit issuance: Receive building permit
  6. Inspections: Required at each phase
  7. Certificate of Occupancy: Required before occupancy

Contact

Phoenix Planning & Development Department 200 W. Washington Street, Phoenix, AZ 85003 Phone: (602) 262-7811 Website: phoenix.gov/pdd

Disclaimer: Verify current requirements with the Phoenix Planning & Development Department. Arizona state law may also affect local ADU regulations.

More about Phoenix Zoning

Building Permits — Cost & TimelineSetbacks & Height Limits

Sources

  1. Arizona HB 2720 (2024) — Accessory Dwelling Units·azleg.gov·Accessed 2026-05-24·Direct link
  2. ARS §9-461.18 — Accessory Dwelling Units; Regulation; Applicability; Definitions·azleg.gov·Accessed 2026-05-24·Direct link
  3. City of Phoenix Planning & Development Department·phoenix.gov·Accessed 2026-05-24·Direct link

FAQ

Are ADUs allowed in Phoenix, Arizona?
Yes. Arizona HB 2720 (2024), codified at ARS §9-461.18, requires Arizona cities with populations greater than 75,000 — including Phoenix — to allow at least one attached, detached, or internal accessory dwelling unit as a permitted use on any lot where a single-family dwelling is allowed. The statute is effective January 1, 2025.
What is the maximum ARS §9-461.18 ADU size?
Under ARS §9-461.18, an ADU may be 75% of the gross floor area of the primary single-family dwelling on the same lot, or 1,000 square feet, whichever is less.
Does Phoenix require owner occupancy for ADUs?
Under ARS §9-461.18, municipalities subject to the statute cannot impose ADU-specific height, lot size, or lot coverage requirements that differ from the primary residence's zoning district. Confirm current Phoenix local implementing rules with the Planning & Development Department.