Building an ADU (casita) in Phoenix
City code and Arizona law · Last reviewed October 9, 2026
Phoenix lets you build two accessory dwelling units (ADUs, or casitas) on a lot with one single-family detached home, and a third on lots of one acre or more if one unit is affordable housing. On lots up to 10,000 square feet, each ADU can be up to 1,000 square feet or 75% of the main house, whichever is less. A detached ADU in the backyard can sit 3 feet from an interior property line and be up to 15 feet tall. The City Council changed the rules in late 2024 to comply with Arizona's ADU law. [1][2]
| ADUs allowed | Two per lot with one single-family detached home; a third on lots of at least 1 acre (43,560 sq ft net) if one ADU is affordable housing [2][3] |
|---|---|
| Not allowed on | Lots with a duplex, triplex, single-family attached units or multifamily units [3] |
| Max size, lots up to 10,000 sq ft | 1,000 sq ft or 75% of the main home's gross floor area, whichever is less [2] |
| Max size, lots over 10,000 sq ft | 3,000 sq ft, 10% of net lot area, or 75% of the main home's gross floor area, whichever is less [2] |
| Detached ADU setbacks | 3 ft from interior side and rear lines, 5 ft from a street side line, 0 ft next to a fully dedicated alley; zone's front setback applies [2][3] |
| Detached ADU height | 15 ft in a required rear or side yard (more with a use permit); outside required yards, same as the main home [2][3] |
| Attached ADUs | One per lot; same height and setbacks as the main home [3] |
| Lot coverage | ADUs count toward your zone's lot coverage limit [2] |
| Parking | State law says a city may not require additional parking for an ADU; the city's guide says a garage or carport conversion needs new equivalent parking. Ask PDD Site Planning [2][4] |
| Short-term rental | Allowed with a city STR permit ($250); owner must live on site if the ADU's certificate of occupancy was issued on or after Sept. 14, 2024 [2][9] |
| Standard plans | Free city ADU standard plans are in review and not yet available (as of October 2026) [1] |
On this page
What you can build in Phoenix
In late 2024, the Phoenix City Council changed its zoning rules to comply with Arizona's ADU law. The city's guide says state law and city ordinance "allow two (and on some parcels three) ADUs per single-family detached house."
- Two ADUs are allowed on a lot with no more than one single-family detached home.
- A third ADU may be allowed when the net lot size is at least 43,560 square feet (one acre) and at least one ADU qualifies as affordable housing, which requires a deed or other restriction on the property.
- Only one of the ADUs can be attached to the house.
- Lots with a duplex, triplex, single-family attached units or any multifamily units can't have an ADU.
An ADU can be part of your existing home, an addition, a converted garage or a new detached building. Phoenix's ADU page warns you to consult the Planning and Development Department before you make decisions about changing your property. [1][2][3]
Size, height and setbacks
Each ADU's size limit depends on your lot:
- Lots up to 10,000 sq ft: 1,000 square feet or 75% of the main home's gross floor area, whichever is less.
- Lots over 10,000 sq ft: 3,000 square feet, 10% of the net lot area, or 75% of the main home's gross floor area, whichever is less.
A garage, carport or attached shade structure built as part of a detached ADU doesn't count toward the ADU's floor area. Shade structures do count toward lot coverage. Every ADU must fit within your zone's lot coverage limit.
Detached ADUs can go in the required rear or side yard. They must be at least 3 feet from an interior side or rear property line and 5 feet from a street side property line. No setback is needed next to a fully dedicated alley. The zone's front setback still applies. In a required rear or side yard, the height limit is 15 feet unless you get a use permit. Outside the required yards, the ADU can be as tall as the main home is allowed to be. A detached ADU can't sit between the house and the front property line without a use permit.
Attached ADUs follow the same height and setback rules as the main home. They may project into the required rear yard to within 3 feet of the rear line and 5 feet of a side line, up to 15 feet tall, unless a use permit allows more.
The city links its September 2024 staff report as the ADU ordinance. That report describes its text as proposed language that may be modified at hearings, and we could not load the city's online zoning code. Confirm the current Section 706.A rules with PDD Site Planning. [2][3]
Design
An attached ADU must be designed so it looks like part of one single-family home, not a duplex, though it can have its own entry. A detached ADU visible from the street should look residential. Phoenix's rules say these guidelines "do not require that an ADU matches the exterior design, roof pitch, or finishing materials" of the main home. State law also says a covered city may not require that kind of matching. [3][4]
Parking and garage conversions
Arizona law says a covered city may not require additional parking to accommodate an ADU, or a fee instead of parking.
Phoenix's ADU guide says converting a garage or carport to an ADU requires new, equivalent off-street parking elsewhere on the lot, dustproofed and not in the front yard setback. Neither source says how these two rules fit together for a garage conversion. Ask PDD Site Planning before you plan a conversion. See our garage conversion guide for general background. [2][4]
Fees
You pay plan review fees when you submit and permit fees when the permit is issued. The city's Preapproved Housing Design Plan Program page points to Phoenix City Code Appendix A.2 for fee amounts.
Phoenix charges development impact fees when a construction permit is issued for a single-family home, with rates that vary by area. The page doesn't say how ADUs are charged. Email impactfees@phoenix.gov or call 602-495-7026 for an estimate for your project. For budgeting help, see our ADU cost guide and financing guide. [5][6][7][8]
Renting your ADU
State law bars Phoenix from stopping you renting the house and the ADU separately on long-term leases of 90 days or more.
The city's guide says "ADUs are allowed to be used as Short-Term Rentals." Every short-term rental needs a city STR permit, applied for in the SHAPE PHX portal, with a $250 non-refundable fee for the initial permit and for each renewal. Since April 4, 2026, if your ADU's certificate of occupancy was issued on or after September 14, 2024, you must submit a notarized statement that you will live on the property, plus proof of address. Questions go to the Short-Term Rental Registry at 602-534-9723. [2][4][9]
Standard and pre-approved plans
Phoenix's ADU Standard Plan Library offers free designs for detached ADUs that came out of the city's 2024 design competition with AIA Phoenix Metro. You must use them without changes; any change means a new submittal outside the program. You still need a plot or site plan. As of our review, all four listed plans were marked "IN REVIEW" and not yet available.
Separately, the city's Preapproved Housing Design Plan Program accepts privately designed plans, including ADUs of 200, 600 or 1,000 square feet. Approved plans are posted with the owner's contact information. You need the plan owner's permission, and any fee for using a plan is between you and the owner. [1][6]
Permit steps in Phoenix
Check your zoning and lot
Look up your zoning district on My Community Map, then find your lot size on the Maricopa County Assessor site. The city notes county records may not match city records. [1][2]
Work out lot coverage and size
Add up everything under roof, including the house, garages, carports, covered patios and every shed or ramada, and compare it with your zone's lot coverage limit. Then check the ADU size limit for your lot size. [2]
Clear up any unpermitted buildings
If you have unpermitted structures, email the PDD Ombudsman at pdd.ombudsman@phoenix.gov to learn how to legalize them before you apply for the ADU permit. [2]
Ask Site Planning about your lot
Questions on whether an ADU is allowed on your property go to the PDD Site Planning Team at pdd.siteplanning@phoenix.gov or 602-495-0302. [2][8]
Prepare plans and the application
For a new building or an addition, submit two sets of plans and calculations plus a plot plan drawn to scale, with a completed Construction Permit/Plan Review Application. If you use a city standard plan, you still need a plot or site plan. [1][2][5]
Plan review
Staff check the submittal for completeness and collect review fees, then review the plans against city codes. If corrections are needed, staff will contact you to fix and resubmit. Any grading and drainage or hillside permit must be issued before the building permit. [5]
Pay permit fees and get the permit
When the plans are approved, you pay the permit fees and the building permit is issued. [5]
Inspections
Schedule inspections through the city; the inspection request line is 602-262-7811. [8]
Pre-approved and sample plans
Free pre-approved detached ADU designs from the city's 2024 design competition, used without changes; all four were still marked "IN REVIEW" in October 2026. [1]
Preapproved Housing Design Plan Program
A city program, under state law, for privately submitted pre-approved plans, including ADUs of 200, 600 or 1,000 sq ft, used with the plan owner's permission. [6]
Who to call
-
Planning and Development Department (PDD)
ADU zoning, plan review, permits and inspections
200 West Washington Street, Second Floor, Phoenix, AZ 85003
-
Residential plan review, ADU and standard plan questions
-
Whether an ADU is allowed on your lot
-
PDD Ombudsman and Customer Advocacy Team
General ADU questions
-
Zoning questions
-
Impact Fees (Growth and Infrastructure)
Impact fee estimates
-
STR permits
Questions people ask
How big can a casita be in Phoenix?
On a lot up to 10,000 square feet, 1,000 square feet or 75% of your house's gross floor area, whichever is less. On larger lots, 3,000 square feet, 10% of the net lot area, or 75% of the house, whichever is less. It must also fit your zone's lot coverage limit. [2]
How close to the property line can I build an ADU in Phoenix?
A detached ADU can be 3 feet from an interior side or rear property line, 5 feet from a street side line, and 0 feet next to a fully dedicated alley. Within those required yards it is limited to 15 feet tall unless you get a use permit. [2]
Can I build an ADU in a Phoenix HOA?
Check your HOA rules first. Phoenix's ADU page says to check HOA rules about accessory structures, and state law does not override private covenants about ADUs. [1][4]
Can I Airbnb my casita in Phoenix?
Yes, with a city short-term rental permit. If the ADU's certificate of occupancy was issued on or after September 14, 2024, you must attest that you will live on the property. [2][9]
Do I need a permit for a small backyard unit?
Phoenix requires permits for all new residential buildings, including detached structures larger than 200 square feet. For a new building or an addition, the city asks for two sets of plans and calculations plus a plot plan. See our tiny house guide for more. [5][10]
Can I get free ADU plans from the city?
The city's ADU standard plans will be free for Phoenix residents once approved, but all four were still in review as of October 2026. Check the city's ADU page for updates. [1]
Sources (10)
- Accessory Dwelling Units (ADU), City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Welcome to the City of Phoenix's Accessory Dwelling Unit (ADU) Guide, City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Staff Report, Zoning Ordinance Text Amendment Z-TA-2-24-Y (September 30, 2024), City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- 9-461.18. Accessory dwelling units; regulation; applicability; definitions, Arizona State Legislature. Accessed October 9, 2026.
- Residential Process Overview, City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Preapproved Housing Design Plan Program, City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Impact Fee Estimates, City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Contact Planning and Development, City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Short-Term Rental Registry, City of Phoenix Planning and Development Department. Accessed October 9, 2026.
- Residential Projects, City of Phoenix Planning and Development Department. Accessed October 9, 2026.