What did HB 2720 change for building a casita or ADU in Arizona?

House Bill 2720, signed in 2024 and codified at A.R.S. 9-461.18, requires Arizona municipalities with a population of at least 75,000 to allow accessory dwelling units (ADUs) on lots zoned for single-family homes, and it caps how restrictive those cities can be. The live answer on casitas covers the basics of what an ADU is; this one focuses on what the statute actually changed and where it does and does not reach.

What the law requires of larger cities

For covered municipalities, the headline is that an outright ban is no longer allowed. A.R.S. 9-461.18 directs these cities to permit ADUs on parcels with an existing or proposed single-family home, and it limits the conditions a city can attach. The guardrails in the statute generally include the following, though each city writes its own implementing ordinance within them:

• At least one ADU per lot. Covered cities must allow at least one attached and one detached ADU on a qualifying single-family lot, subject to the size and setback limits below.
• No owner-occupancy requirement. A city cannot force the property owner to live on site as a condition of having an ADU.
• Limited parking demands. The statute restricts a city from requiring more than a modest amount of added parking for an ADU.
• Size floors. A city cannot cap an ADU below the thresholds set in the statute, which protect a meaningful minimum floor area rather than letting a city permit ADUs in name only.
• Setbacks no stricter than the main home. ADU setbacks generally cannot be made more restrictive than those that apply to the primary dwelling.
• No familial-use limits. A city cannot require that the ADU be occupied only by family members.

Cities were directed to bring their ordinances into compliance on the timeline set by the law, so by 2026 the larger Phoenix-metro jurisdictions have adopted implementing rules. Among the markets we build in, Scottsdale and Phoenix clear the 75,000-resident threshold and are covered.

What the law does not change

HB 2720 sets a floor, not a free pass. Several things still govern whether and how you can build:

• Smaller towns are not covered. Cave Creek, Carefree, Fountain Hills, and similar towns fall under the 75,000-resident threshold, so the statewide mandate does not apply and their local zoning controls.
• Unincorporated county land is separate. Parcels governed by Maricopa County or Pinal County, including much of Rio Verde Foothills, follow county zoning rather than a city ADU ordinance.
• Septic and water capacity still bind. On a lot served by a well and septic, a second dwelling can require a larger or upgraded onsite wastewater system reviewed under Arizona Department of Environmental Quality standards, regardless of what zoning allows.
• Short-term rental is regulated separately. The law addresses the right to build an ADU, not the right to operate it as a nightly rental; those rules live in other ordinances and change.
• Overlays still apply. Hillside, open-space, and design-review rules continue to shape where an ADU can sit even in a covered city.

Why the distinction matters for your lot search

Two parcels a few miles apart can now carry very different ADU rights purely because one sits in a city above the population threshold and the other in a small town or unincorporated county. If a casita or future rental is part of your plan, the jurisdiction is worth confirming before you make an offer, not after.

How Jematell Homes helps

We design custom homes with casitas and ADUs across the metro and tailor each unit to the lot's jurisdiction, zoning, and your goals, whether that is multigenerational living, guests, a home office, or a future rental. Because ADU rules are recent and each covered city implements A.R.S. 9-461.18 differently, and because small towns and county land are outside the statewide mandate, we confirm the current standards with your local AHJ, and any applicable HOA, before finalizing a design.