Arizona's ADU law (HB 2720), explained
Updated October 9, 2026
Short answer: since 2025, Arizona cities with more than 75,000 people must let homeowners build a casita (accessory dwelling unit, or ADU) on any lot where a single-family home is allowed, with no public hearing. The rules come from A.R.S. § 9-461.18, passed in 2024 as HB 2720.
What cities have to allow
- Two ADUs per lot: one attached to the house and one detached, both as a "permitted use", which means no hearing, variance or special permit.
- A third on big lots: on lots of one acre or more, one more detached ADU, if at least one ADU on the lot is rented as restricted-affordable housing.
- A minimum size they must allow: 75% of the main home's living area or 1,000 sq ft, whichever is smaller. A city may allow bigger.
- Setbacks of no more than 5 ft from the side and rear property lines.
- No stricter rules than for the house: height, setbacks, lot size, lot coverage and frontage can't be stricter for an ADU than for a single-family home in the same zone.
What cities can't require
- Extra parking, or a fee instead of parking.
- That you live on the property, or that the tenant is a relative or employee.
- That the ADU matches the house's design, roof pitch or materials.
- Street improvements (other than fixing streets damaged by the work), or a restrictive covenant.
- Commercial building codes or fire sprinklers. Normal residential building, fire and health codes still apply.
How big can mine be?
| Your home's living area | Largest ADU the city must allow |
|---|---|
| 800 sq ft | 600 sq ft |
| 1,000 sq ft | 750 sq ft |
| 1,200 sq ft | 900 sq ft |
| 1,334 sq ft or more | 1,000 sq ft |
Living area is the home's interior habitable space, not the garage. Your lot can still limit the size: the ADU has to fit inside the setbacks, and the house, garage and ADU together must stay under your zoning district's lot coverage limit.
What the law doesn't change
- HOAs and CC&Rs. The law limits cities, not private deed restrictions.
- Utility easements. You can't build over a public utility easement without written consent from the utilities that use it.
- Short-term rentals. The law protects long-term rentals; Airbnb-style rentals follow your city's and HOA's rules.
- Smaller towns and county land. Towns under 75,000 people and unincorporated "county islands" are not covered.
Type your Mesa or Tempe address. CasitaFlow pulls your parcel and zoning and shows the largest casita allowed, the setbacks, and a drawing of where it fits. Free, no account needed.
Common questions
Does Arizona's ADU law apply to my city?
It applies to cities and towns with more than 75,000 people. In the Valley that includes Phoenix, Mesa, Tempe, Chandler, Gilbert, Scottsdale, Glendale, Peoria, Surprise and others. Smaller towns and unincorporated county areas set their own rules.
How big can a casita be in Arizona?
Cities must allow an ADU up to 75% of the main home's living area or 1,000 square feet, whichever is smaller. A city may allow larger, but not smaller.
How many ADUs can I build?
Cities must allow one attached and one detached ADU on a lot where a single-family home is allowed. On lots of one acre or more, a third (detached) ADU is allowed if one of the ADUs is rented as restricted-affordable housing.
Can I rent out my casita?
Yes, as a long-term rental (90 days or more, or month to month). Cities can't ban that, can't require you to live on the property, and can't require the tenant to be family. The law doesn't cover short-term rentals, so check your city's rules and your HOA.
Do I need extra parking for an ADU?
No. Cities can't require added parking or a fee instead of parking for an ADU.
Can my HOA still say no?
Possibly. The law limits what cities can require; it doesn't cancel private deed restrictions (CC&Rs). Read your HOA's rules before you design anything.
Source: A.R.S. § 9-461.18, Accessory dwelling units (Arizona Legislature).