Everything homeowners need to know about building a casita or accessory dwelling unit in Phoenix - size limits, setbacks, permits, and how Arizona's statewide "Casita Bill" reshaped the city's rules.
Last verified: September 2026
7/10 · ADU-friendly
1,000 sq ft*
Max ADU size
15 ft*
Max height
Not required*
Owner-occupancy
By-right
Permit type
This page summarizes the City of Phoenix Zoning Ordinance (Section 706, Accessory Uses and Structures) as amended to comply with Arizona House Bill 2720, for general reference - it is not legal advice. Regulations change; always confirm current requirements with the Phoenix Planning & Development Department (PDD) before designing or applying for permits. See sources below.
Zoning & size requirements
What you're allowed to build
ADU type
Max size
Max height
Notes
Detached casita / ADU
The lesser of 75% of the primary home's gross floor area or 1,000 sq ft, on lots up to 10,000 sq ft (up to 3,000 sq ft on larger lots)
15 ft when sited within the required rear or side yard; taller with use permit approval
May not sit between the primary home and the front property line without a use permit
Attached ADU (addition, above garage)
Same overall size formula as a detached unit
Generally matches the primary structure
Counts toward Phoenix's one-attached-plus-one-detached allowance per lot
How many ADUs are allowed
Arizona passed a statewide ADU mandate in 2024 (House Bill 2720), which applies to cities with 75,000+ residents, including Phoenix. Phoenix allows up to two ADUs per single-family lot (one attached and one detached) in typical single-family residential zones. A third may be permitted on lots of at least one acre if one of the units qualifies as affordable housing. Confirm your parcel's zoning district with PDD.
Additional standards
Setbacks, parking & other rules
Setbacks
State law caps what Phoenix can require at 5 ft or less for side and rear yards for a qualifying ADU
Parking
No additional off-street parking may be required specifically for an ADU, under state law
Units per lot
Up to 2 ADUs (1 attached + 1 detached) in addition to the primary home; a 3rd is possible on lots of 1+ acre with an affordable-housing unit
Owner-occupancy
Not required to build or rent an ADU. The city may require owner-occupancy of the primary home or the ADU only if the unit is used as a short-term rental
Building code
Must meet the City of Phoenix's adopted residential building code
Short-term rental
Phoenix cannot ban ADUs from being used as short-term rentals under state law, though owner-occupancy of one of the two units may be required for that use
Ordinance history
How Phoenix's ADU rules got here
Pre-2023Casitas largely off-limits. Phoenix's zoning code did not generally allow separate, livable backyard structures on typical single-family lots.
2023Phoenix legalizes ADUs locally. In September 2023, City Council voted 8-1 to allow single-family homeowners to build one ADU per property, with city-set limits on size and height, a ban on short-term rental use, and required water and electrical service.
2024Arizona passes HB 2720. Governor Katie Hobbs signed the "Casita Bill" on May 21, 2024, requiring cities with 75,000+ residents to allow at least one attached and one detached ADU per single-family lot by right, and barring cities from banning ADU short-term rentals.
2024Phoenix updates its ordinance. In November 2024, City Council approved a zoning ordinance text amendment lifting the city's ADU short-term-rental ban and aligning local rules with the state mandate ahead of the compliance deadline.
2025HB 2720 takes effect statewide. As of January 1, 2025, cities that hadn't updated their codes saw ADUs become allowed on all residential lots without the usual local restrictions - Phoenix had already acted.
Worth knowing: Phoenix's original 2023 ordinance was more restrictive than what state law now requires, and city officials were vocal about their reluctance to lift the short-term-rental ban. Local reporting characterized the city's 2024 update as a required response to state preemption rather than a locally driven policy change.
Permit process
How Phoenix ADU permitting works
1
Pre-application zoning check
Confirm your lot's zoning district and ADU eligibility with PDD before you design.
2
Prepare your site plan
Show the ADU's size, height, location, and setbacks, along with planned utility connections.
3
Consider a standard plan
Phoenix offers pre-approved standard ADU plans at no design cost, which can speed up review compared to a fully custom design.
4
Submit through Shape Phoenix
File your application online through the city's Shape Phoenix portal, or in person at Phoenix City Hall.
5
Plan review
City staff check for zoning and building code compliance; simple projects can clear review in a few weeks, more complex ones take several months. Expect at least one round of revisions.
6
Permit issuance, inspections & occupancy
Once approved, begin construction and schedule staged inspections; a final inspection results in a certificate confirming the ADU is legal to occupy.
Impact fees apply and vary by ADU size and location within the city. Fees and timelines are approximate - confirm current figures with the Planning & Development Department.
Budgeting
What it costs to build an ADU in Phoenix
Garage conversion
Roughly $80,000-$150,000
Mid-size detached casita (500-800 sq ft)
Roughly $150,000-$250,000
Larger or custom-finish casita
Roughly $250,000-$400,000+
Impact & permit fees
Vary by ADU size and location; confirm current amounts with PDD before budgeting
These are general ranges from local contractor estimates and regional reporting, not quotes - lot conditions, utility distance, and finish level are the biggest swing factors. Phoenix's PDD also offers standard, pre-approved ADU plans at no design cost, which can meaningfully lower the design portion of your budget.
Before you apply
Tips for a smooth approval
Ask about standard plans first. Phoenix's pre-approved standard ADU plans skip the custom design fee and can move through review faster than a one-off design.
Confirm your setback and height numbers before you design. State law caps what the city can require, but your specific lot and zoning district still determine the final building envelope - verify with PDD.
Decide on short-term rental plans early. If you want to use the ADU (or your home) as a short-term rental, you may need to plan for owner-occupancy of one of the two units.
Budget separately for impact fees. These are billed on top of standard plan review and building permit fees and vary by ADU size and location.
Don't plan on a basement. Desert soil conditions make basements uncommon and costly in Phoenix - most detached ADUs here are slab-on-grade.
FAQ
Common questions
Do I need to live on the property to build an ADU in Phoenix?
No, not generally. Owner-occupancy is only required if you use the ADU or the primary home as a short-term rental.
How many ADUs can I build?
Up to two per single-family lot (one attached, one detached); a third is possible on lots of at least one acre if one qualifies as affordable housing.
What's the maximum size for a detached ADU?
The lesser of 75% of your primary home's floor area or 1,000 sq ft on lots up to 10,000 sq ft; up to 3,000 sq ft on larger lots.
Do I need extra parking for an ADU?
No. State law bars cities from requiring parking specifically for an ADU.
Can I rent my ADU on Airbnb or another short-term platform?
Yes. State law prevents Phoenix from banning it outright, though the city may require owner-occupancy of one of the two units if you do.
How long does the permit process take?
Simple projects using a standard, pre-approved plan can clear review in a few weeks; custom, complex projects can take several months.
How much does an ADU cost to build in Phoenix?
Garage conversions typically run $80,000-$150,000; a mid-size detached casita commonly runs $150,000-$250,000, with larger or custom units running $250,000-$400,000 or more, based on local contractor estimates and regional reporting.
Does Arizona have a statewide ADU law?
Yes. House Bill 2720, the "Casita Bill," took effect January 1, 2025, and requires cities with 75,000+ residents, including Phoenix, to allow at least one attached and one detached ADU per single-family lot by right.
Did Phoenix want these changes?
Not entirely. Phoenix had already adopted its own, more restrictive local ADU ordinance in September 2023; the 2024 update was made to comply with the state's new preemption law, and city officials publicly expressed reluctance about losing local control, particularly over short-term rentals.
