Can You Build a Casita in Arizona? The 2026 ADU Law, Explained

Last updated August 19, 2026 by Josh Hogan, Live AZ Co.

What did Arizona's casita law actually change?

Two laws, a year apart. House Bill 2720, signed in May 2024, added A.R.S. § 9-461.18 and gave cities over 75,000 people until January 1, 2025 to allow accessory dwelling units. House Bill 2928, signed in May 2025, added A.R.S. § 11-810.01 and gave counties until January 1, 2026.

Both carry the same penalty for missing the deadline: accessory dwelling units are then allowed on all residentially zoned lots in that jurisdiction without limits. Maricopa County adopted its own update rather than take the default, heard by the Board of Supervisors on November 19, 2025 (case TA250002).

An accessory dwelling unit, called a casita here, is a second dwelling with its own kitchen, bathroom and entrance on a lot that already has a house. A converted garage counts. So does a standalone building in the backyard.

Does the casita law apply to my house in Gilbert, Chandler, Mesa, or Tempe?

If your house sits inside Mesa, Gilbert, Chandler, Tempe, or Scottsdale, the city law has applied since January 1, 2025. If it sits on unincorporated county land, the county law has applied since January 1, 2026. A town under 75,000 residents falls outside both statutes, so its own zoning code controls.

Queen Creek sits close enough to the population line to confirm with the town rather than assume.

How big can an Arizona casita be, and where can it sit on the lot?

The size your city or county has to allow is 75% of your home's gross floor area or 1,000 square feet, whichever is less. On a 1,600 square foot house that math lands at the 1,000 square foot cap. On a 1,100 square foot house it lands at 825 square feet. A jurisdiction may allow more, and it cannot allow less.

The statutes also strip out the requirements that used to end these projects. Under A.R.S. § 9-461.18 your city cannot:

• Require additional parking for the unit, or charge a fee in place of it
• Require the casita to match the exterior design, roof pitch, or finish materials of the main house
• Require a familial, marital, or employment relationship between you and whoever lives in it
• Set rear or side setbacks more than five feet from the property line
• Apply height, setback, lot size, or lot coverage rules stricter than those on your house
• Prohibit leasing the casita, or the main house, as separate long-term rental housing

One attached unit and one detached unit is the floor on a normal lot. On a lot of an acre or more, the county statute contemplates one additional detached unit, with conditions.

Short-term rental is the exception worth reading twice. What the ADU statutes protect is long-term leasing, defined as a lease of 90 days or longer or month to month. Short-term rental is governed elsewhere, and on the county side the statute permits an owner-occupancy requirement for a short-term rental in a unit that received final approval on or after September 14, 2024.

Can my HOA still stop me from building a casita?

Yes, and this is the gate that decides most East Valley lots. Both statutes deliberately left private agreements alone. A.R.S. § 9-461.18 states that the section "does not prohibit restrictive covenants concerning accessory dwelling units entered into between private parties." Your city cannot condition your permit on signing one. An existing covenant still binds you.

So much of Gilbert, Chandler, Queen Creek and south Mesa was built as master-planned community with recorded CC&Rs that this is the first thing to check, not the last. Pull the recorded declaration from the county recorder, not the welcome packet handed to you at closing, and read the sections on accessory structures, second dwelling units, rentals, and lot coverage. Ambiguous wording is worth an attorney's hour first.

What does a casita actually do to what my house is worth?

It depends on what you build and whether you permitted it, and any number quoted without seeing your lot is a guess. What can be said plainly: an appraiser measures finished, permitted square footage. Work done without a permit usually cannot be counted the same way, and it becomes a disclosure item at resale.

In a February 2026 planning session with clients weighing a build in the East Valley, the working number from a contractor was roughly $200 per square foot for a detached casita, with quotes in the market ranging from about $150 to $600 per square foot depending on finish. A 600 square foot unit penciled around $120,000 on that basis.

That conversation belongs ahead of the design one, because adding space and redoing space are different animals. Put square footage into a house, even a guest house, and an appraiser has something measurable to work with. Tear out a kitchen and put in a new one, and the return is an opinion about finishes. Both belong in a comp analysis on your street first, which is where a home valuation starts.

If you are shopping instead of building: homes with a permitted casita rarely come up for sale in Gilbert or the rest of the East Valley. The owners built them for a reason and are not moving.

How do I keep from getting scammed by a casita contractor?

Verify the license before you write a check. On April 14, 2026, Arizona Attorney General Kris Mayes warned homeowners about construction fraud aimed at ADU projects: the company collects a large deposit, never pulls permits, and never breaks ground, with reported losses reaching $250,000 (Arizona Attorney General's Office, April 2026).

Four checks:

1. Confirm an active license with no unresolved complaints at roc.az.gov or 1-877-692-9762
2. Get more than one written bid, each with scope of work, materials, timeline, and total price including labor
3. Refuse a large payment up front, and refuse payment by cash, Zelle, cryptocurrency, or gift card
4. Ask to see the actual permit application, not a claim that permits are "in process"

Live AZ Co keeps a contractor directory of trades the team has used on real transactions, which is a reasonable place to start a bid list.

Frequently asked questions

Do I still need a permit to build a casita in Arizona?

Yes. The law makes an accessory dwelling unit a permitted use, which removes the rezoning, the hearing, and the special-use approval. It does not remove the building permit or the inspections. An unpermitted unit is a disclosure item at resale and cannot be treated as finished square footage by an appraiser.

Can my HOA stop a casita in Arizona?

Yes. Both HB 2720 and HB 2928 left private covenants intact. A.R.S. § 9-461.18 states the section does not prohibit restrictive covenants concerning accessory dwelling units entered into between private parties. If your recorded CC&Rs bar a second dwelling or a detached structure, the state law does not override them.

How big can a casita be in Gilbert or Mesa?

The size the city must allow is 75% of the gross floor area of your house or 1,000 square feet, whichever is less. A 1,600 square foot home reaches the 1,000 square foot cap. A 1,100 square foot home is limited to 825 square feet. A city may permit more than the statutory floor but cannot permit less.

Can I rent out my casita?

Long-term leasing is protected. Cities and counties cannot prohibit leasing the casita or the main house as separate long-term rental housing, with long-term defined as 90 days or longer or month to month. Short-term rental sits under separate law, and on the county side an owner-occupancy requirement is permitted for a unit approved on or after September 14, 2024.

Where do I start if I am deciding between building and moving?

Start with the three gates: your recorded CC&Rs, the size your lot and house allow, and a real bid from a licensed contractor. Then compare that total against what the same space costs as a move. Josh Hogan and Jacqui Shoffner have bought and sold 501 homes across the East Valley, and that comparison is worth running before the design one. See selling for the other side of the math.

Josh Hogan | Live AZ Co | Real Broker AZ, LLC #LC696641000 | Equal Housing Opportunity