What's Required in Phoenix
- Two ADUs permitted per lot with one single-family detached home; third with an affordable unit on a 43,560 sq ft lot; none on duplex, triplex or multifamily lots (Zoning 608.E.2 as amended)
- Size: 75% of the house's gross floor area, max 1,000 sq ft on lots up to 10,000 sq ft; lesser of 3,000 sq ft or 10% of net lot area above that (Zoning 706.A.8)
- Detached ADU setbacks in required yards: 5 ft street side, 3 ft interior side or rear, 0 ft at a dedicated alley; 15 ft height, more by use permit
- Attached ADU follows the house's setbacks and height; may project to 5 ft side and 3 ft rear at up to 15 ft
- Lot coverage of the district applies; 40% one-story allowance in RE-43, RE-24, R1-14 and RE-35
- Fee: Table A on $170.80/sq ft valuation plus 80% plan review over $50,000; $98 plot plan review; impact fees and water/sewer fees where applicable
- Garage conversions must replace the parking with dustproof spaces outside the front setback
- No fire sprinkler or commercial code may be required; no ADU on a public utility easement without utility consent (ARS 9-461.18)
- Owner-occupant may act as GC under ARS 32-1121.A.5; otherwise ROC-licensed contractor
Can You Build an ADU in Phoenix?
Yes, and since 2025 state law sets much of the rule book. Arizona's HB 2720, now ARS 9-461.18, requires cities to allow at least one attached and one detached accessory dwelling unit as a permitted use on any lot where a single-family home is allowed, sized at 75 percent of the gross floor area of the house or 1,000 square feet, whichever is less, with side and rear setbacks of no more than 5 feet, no added parking and no design-matching rule. Phoenix amended its Zoning Ordinance in late 2024 to comply: when a lot has no more than one single-family detached primary dwelling, two ADUs are permitted, and a third when one qualifies as affordable housing and the net lot is at least 43,560 square feet.
Phoenix ADU Rules by Scenario
| What you are doing | City filing | Rule |
|---|---|---|
| New detached ADU on a lot up to 10,000 sq ft | Building permit; ADU up to 1,000 sq ft or 75% of the house, whichever is less | Zoning 706.A.8 as amended; ARS 9-461.18 |
| Detached ADU on a lot over 10,000 sq ft | Building permit; lesser of 3,000 sq ft, 10% of net lot area, or 75% of the house | Zoning 706.A.8.b |
| Detached ADU in the required rear or side yard | Permit; 5 ft street-side, 3 ft interior side/rear, 0 ft at an alley; 15 ft height | Zoning 706.A.4 |
| Attached ADU or addition to the house | Building permit; same setbacks and height as the house; may project to 5 ft side / 3 ft rear at 15 ft | Zoning 706.A.6; 701.A.3 as amended |
| Garage or carport conversion | Building permit; replacement dustproof parking outside the front setback | Beginner's Guide to ADUs |
| ADU using a city standard plan from the ADU Standard Plan Library | Plot plan and permit; plans free; no modifications allowed | ADU page (plans in review) |
| ADU in front of the house, or over 15 ft in a required yard | Use permit under Section 307 first | Zoning 706.A.4 and 706.A.5 |
How Much Does an ADU Permit Cost in Phoenix?
The 2026 Development Fee Schedule (Appendix A.2, effective January 20, 2026) prices new construction on valuation: building square footage times the standard rate for the occupancy. The city's Building Valuation Table lists R-3 one- and two-family, Type VB at $170.80 per square foot. A 600-square-foot detached ADU is therefore 600 x $170.80 = $102,480. Table A charges $703 on the first $50,000 plus $9 for each additional $1,000 or fraction, so the permit fee is $703 + 53 x $9 = $1,180. Residential plan review on projects over $50,000 is 80% of the permit fee, another $944, for about $2,124. A 400-square-foot unit ($68,320) is $874 + $699, about $1,573; a 1,000-square-foot unit ($170,800) is $1,792 + $1,434, about $3,226. Add the $98 plot plan review. Those are the building department's fees only: the city collects development impact fees at permit issuance in its growth-area impact fee zones, and water and sewer fees for meters and service are separate, so ask the Growth and Infrastructure team what applies to your address before you budget.
Size, Placement and Lot Coverage
An ADU may not exceed 75 percent of the primary home's gross floor area, capped at 1,000 square feet on lots up to 10,000 square feet and at the lesser of 3,000 square feet or 10 percent of net lot area on larger lots; a garage, carport or attached shade structure built with a detached ADU does not count toward its floor area. A detached ADU may sit in the required rear or side yard at 5 feet from a street-side line and 3 feet from an interior side or rear line, with no setback at a fully dedicated alley, up to 15 feet tall; outside the required yards it may be as tall as the house. It may not sit between the house and the street without a use permit. Every ADU must fit the lot coverage limit for the zoning district, which the 2024 amendment raised to 40 percent in the RE-43, RE-24, R1-14 and RE-35 districts when all structures are one story.
Who Files and What They Submit
The city offers appointments for custom homes and ADUs, and applications go through SHAPE PHX with a plot plan showing the number of existing and proposed units, setbacks, easements and a lot coverage table, plus full construction drawings sealed where the Board of Technical Registration requires. An owner-occupant may act as general contractor under ARS 32-1121.A.5; a unit built to rent within a year should be built by an ROC-licensed contractor. State law bars the city from requiring a fire sprinkler or a commercial code for an ADU, and bars building on a public utility easement without the utilities' written consent. Permits expire 24 months after issuance, and a certificate of occupancy follows the final inspection.
How to Get a ADU Permit in Phoenix
Check zoning and lot coverage
Find your district in My Community Map, total everything under roof, and confirm the ADU fits the coverage allowance and the 75% / 1,000 sq ft size cap.
Pick a design
Custom plans sealed as the Board of Technical Registration requires, or a city standard plan from the ADU library once approved, used without modification.
Book a residential appointment and apply in SHAPE PHX
Residential Construction Permit/Plan Review Application, plot plan with units, setbacks, easements and lot coverage table, full drawings; plan review fee at intake.
Pay permit, plot plan and other city fees
Table A permit fee after approval, $98 plot plan review, plus any development impact fees and water and sewer fees for the address.
Build through inspections to certificate of occupancy
Footings, framing, pre-drywall and final inspections; the certificate is issued after the final inspection.