Everything homeowners ask about building an ADU in Phoenix — answered with 2026 data.
Yes, ADUs are allowed in Single-family residential zones in Phoenix, AZ. The maximum size for a detached ADU is 1,000 sq ft on lots up to 10,000 sq ft (75% of primary dwelling, whichever is less); on lots over 10,000 sq ft, the lesser of 3,000 sq ft or 10% of net lot area. Attached ADUs can be up to 75% of primary dwelling, capped at 1,000 sq ft (lots ≤10,000 sq ft). Phoenix has an ADU-friendliness score of 6/10. Check our full Phoenix ADU rules page for complete zoning details.
ADU construction in Phoenix typically costs $120,000-$240,000. The cost per square foot averages $135-$270. Garage conversions are more affordable at $60,000-$140,000, while prefab ADUs cost $85,000-$200,000. Permit fees add $2,500-$4,200 to your budget. See our detailed Phoenix ADU cost guide.
Detached ADUs in Phoenix can be up to 1,000 sq ft on lots up to 10,000 sq ft (75% of primary dwelling, whichever is less); on lots over 10,000 sq ft, the lesser of 3,000 sq ft or 10% of net lot area. Attached ADUs are limited to 75% of primary dwelling, capped at 1,000 sq ft (lots ≤10,000 sq ft). Junior ADUs (JADUs) have a cap of Not allowed. Maximum height is 15 ft when within required rear/side yards (greater height may be allowed with use permit). You are allowed up to 2 per lot (1 attached + 1 detached); a 3rd detached ADU allowed on lots 1+ acre if at least one unit is restricted-affordable on a qualifying lot.
Rear setback: 5 feet (3 ft for some detached configurations per ZO 706; statute caps rear/side at 5 ft). Side setback: 5 feet (3 ft for some detached configurations per ZO 706). Front setback: Per underlying zoning district (no ADU-specific front setback beyond zone standard) — Confirm with Phoenix Planning. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
No additional parking required (ARS 9-461.18 / AZ HB 2720 prohibits ADU-specific parking mandates). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required for long-term rental; owner must reside on-site only if an ADU built on/after Sept 14, 2024 is used as a short-term/vacation rental. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Phoenix is typically 60-90 days. Plan check: 2-3 weeks. Pre-approved plans availability: Limited availability.
Average ADU rental income in Phoenix: 1-bedroom units rent for $1,250-$1,700/month, 2-bedroom units for $1,600-$2,200/month. Short-term rentals: Varies by neighborhood. Expected ROI: 7-10% annual return.
The minimum lot size for an ADU in Phoenix is No ADU-specific minimum; an ADU is allowed on any lot with a permitted single-family dwelling (the smallest single-family district, R1-6, has a 6,000 sq ft minimum lot). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Phoenix, a garage conversion typically costs $60,000-$140,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.