The short answer: Arizona ADU law (HB 2720), signed in May 2024 and codified at A.R.S. section 9-461.18, requires municipalities with more than 75,000 residents to allow at least one attached and one detached ADU on single-family lots. ADUs can be limited to 75% of the main house’s floor area or 1,000 sq ft, whichever is smaller. Cities cannot require extra parking, cannot require a family or employment relationship between the owner and the occupant, and cannot impose side or rear setbacks above 5 feet. Cities had until January 1, 2025 to adopt compliant regulations.
Last verified: October 2, 2026 ยท Written by the ADU Scope editorial team
Key fact: According to an Arizona State University brief, HB 2720 affects 16 municipalities (Phoenix, Tucson, Mesa, Chandler, Gilbert, Glendale, Scottsdale, Peoria, Tempe, Surprise, Goodyear, Buckeye, Yuma, Avondale, Flagstaff and Queen Creek). The statute does not list the covered cities, so this list is an estimate: Flagstaff exceeds 75,000 on census data, while Queen Creek (59,308 in the 2020 census) qualifies only on recent population estimates. If your town has fewer than 75,000 residents, the state mandate does not apply and local zoning decides.
Who the Arizona ADU Law Applies To
HB 2720 covers municipalities with a population above 75,000. The bill excludes tribal lands and areas affected by military airports and FAA-licensed or general aviation airports, which means some parcels near airports may not benefit from the mandate even inside a covered city.
The ASU Morrison Institute brief reports that before the law, most Arizona cities allowed only one ADU per parcel, only two permitted ADUs in all residential zones, at least four required off-street parking, and many applied height limits stricter than those for main houses. The law was designed to standardize those rules across large cities.
What happens if a city did not update
The bill text provides that municipalities had to adopt development regulations by January 1, 2025. If they did not, ADUs become allowed on all residential parcels without restrictions, according to the legislative summary. In practice, you should check the current city code and, if it appears outdated, ask the planning department which state provisions it applies.
Tip: Ask your planning department whether the city’s ADU code was updated for HB 2720, and request the section number. If the answer is unclear, put the question in writing.
How Many ADUs and How Large Under Arizona ADU Law
On a lot zoned for single-family homes, covered cities must allow a minimum of one attached ADU and one detached ADU as permitted uses. A third detached ADU is allowed on parcels of one acre or more if at least one of the units is restricted as affordable.
| Topic | HB 2720 rule |
|---|---|
| Number of ADUs | At least one attached and one detached |
| Extra detached ADU | On parcels of one acre or more, if at least one unit is restricted-affordable |
| Maximum size | 75% of the main house’s gross floor area or 1,000 sq ft, whichever is smaller |
| Height | Must match regulations for primary structures |
| Side and rear setbacks | Cannot exceed 5 feet |
The 75% or 1,000 sq ft rule works the same as Portland’s approach to size: a small house limits a new ADU. A 1,200 sq ft house, for example, allows an ADU up to 900 sq ft (75% of 1,200), while a 2,400 sq ft house allows up to 1,000 sq ft.
Why the setback rule matters
Cities cannot require more restrictive height, setbacks, lot size, coverage or building frontage than apply to single-family homes, and they cannot require rear or side setbacks above five feet. That second rule is the practical one for backyard units: on a typical lot, a five-foot limit leaves much more usable space than a 10- or 15-foot setback.
What Cities Cannot Require Under Arizona ADU Law
The bill lists several prohibitions that remove common barriers.
- Family, marital or employment relationships between the owner and occupant.
- Additional parking or parking fees.
- Matching exterior design, roof pitch or finishing materials to the main house.
- Public street improvements unless directly affected by the project.
- Restrictive covenants on residential-zoned parcels, as stated in the legislative summary.
- Separate advertising restrictions from those on the main dwelling.
The ASU brief also states that cities must allow the main house and the ADU to be rented long term. Before the law, some cities limited who could live in an ADU, for example only relatives. That is no longer allowed in covered cities.
Attention: The “restrictive covenants” item in the legislative summary does not clearly say HOA rules are void. It is not clear how courts or associations apply it, so treat HOA documents as potentially binding until an attorney tells you otherwise (see our article on HOAs).
Owner Occupancy and Short-Term Rentals
For ordinary long-term use, Arizona cities cannot require owner occupancy or any relationship between owner and tenant. Short-term rentals are different. The legislative summary says vacation or short-term rental operators must live on site if the ADU was built after the effective date and functions as a vacation rental. The ASU brief adds that other state statutes allow cities to impose short-term rental limits, including owner-occupancy requirements for ADUs with a certificate of occupancy or final approval on or after September 14, 2024 (A.R.S. section 9-500.39).
Put simply: you can generally rent an ADU long term without living there, but if you plan to use it as an Airbnb, you may need to live on the property, depending on when it was built and your city’s rules.
| Use | Owner-occupancy rule |
|---|---|
| Long-term rental | Cannot be required |
| Family or personal use | Cannot be required |
| Short-term rental in a post-effective-date ADU | Operator may need to live on site |
Practical Steps Under Arizona ADU Law
- Confirm your city has more than 75,000 residents.
- Check your parcel for airport or tribal-land exclusions.
- Read your city’s current ADU section and compare it with the table above.
- Check HOA or deed restrictions.
- Get a written fee estimate, since neither HB 2720 nor its summaries mention caps on permit or plan-check fees.
- Decide early whether the unit will be a long-term rental, family housing or a short-term rental.
Fees deserve a note. HB 2720 itself does not set fee caps, but a separate 2026 law (HB 2946, which added subsection U to A.R.S. section 9-463.05; confirm its effective date) limits development fees on ADUs: water and wastewater fees may not exceed the incremental increase in demand, and other fees may not exceed the lesser of 25% of the total development fees or the proportionate share for a single-family home. ADUs are not fee-free, so ask the city for a written estimate.
Frequently Asked Questions
Does HB 2720 apply to every Arizona city?
No, only municipalities with more than 75,000 residents, which the ASU brief counts as 16.
How many ADUs can I build?
At least one attached and one detached; a third on parcels of one acre or more if one unit is restricted-affordable.
Can the city require extra parking?
No. It cannot require additional off-street parking or parking fees.
Do I have to live on the property?
Not for long-term rentals. Short-term rentals may be subject to owner-occupancy rules.
How big can the ADU be?
75% of the main house’s gross floor area or 1,000 sq ft, whichever is smaller.
Next Steps
- ADU Laws by State: A 50-State Overview
- Owner-Occupancy Rules for ADUs: Key States Compared
- Can My HOA Block an ADU? Rules by State
- ADU Impact Fees: When You Pay Them and How to Avoid Them
- ADU Setback Requirements Explained: California, Washington, Colorado and Portland
General information, not legal advice. Local rules vary and change; confirm with your planning department.
Sources: Arizona Legislature: HB 2720 summary (transmitted) ยท ASU Morrison Institute: Accessory Dwelling Units and HB 2720 in Arizona ยท A.R.S. 9-461.18 ยท A.R.S. 9-463.05 ยท A.R.S. 9-500.39