Why casitas only started to make sense in 2024

For decades a casita in the Phoenix area meant a variance hearing, a parking requirement, a rule that you live on site, and a design review that could kill the project. On May 21, 2024 the state took most of that off the table. Here is exactly what changed, why it changes the economics, and where it applies.

The one-paragraph version

House Bill 2720, signed by Governor Katie Hobbs on May 21, 2024, became A.R.S. § 9-461.18. It requires every Arizona city with more than 75,000 residents to allow at least one attached and one detached accessory dwelling unit on any lot with a single-family home, as a permitted use, without a hearing, a variance, an owner-occupancy requirement, extra parking, or design matching. Cities had until January 1, 2025 to adopt compliant rules; a city that did not would have lost the ability to regulate ADUs at all. A 2025 follow-up extended the same framework to counties, and a third law requires cities to offer pre-approved ADU plans.

Before and after

Question	Before 2024 (typical)	Now, in covered cities
Can I build one?	Often only with a use permit or variance and a public hearing, where neighbors could object.	A permitted use. Building permit only; no hearing, no variance.
Do I have to live on the property?	Many cities required owner occupancy.	No. The city cannot require any relationship between owner and occupant.
Can I rent it?	Rules varied; some cities limited or barred separate rental.	Yes, long-term (90 days or more, or month to month). The city cannot prohibit renting the house and the casita separately.
Do I need to add parking?	Usually one or more extra spaces, which many lots could not fit.	No additional parking, and no fee in place of it.
How big?	Caps of 400 to 800 sq ft were common, often as a percent of the main house.	At least 75% of the main home or 1,000 sq ft, whichever is smaller. Phoenix goes further on large lots.
Where on the lot?	Setbacks as for a house, sometimes 10 to 20 ft.	Rear and side setbacks of no more than 5 feet; height and coverage rules no stricter than the house.
Does it have to match the house?	Design review in some cities.	The city cannot require matching exterior design, roof pitch or materials.

Statute: A.R.S. § 9-461.18 (accessory dwelling units; municipalities). Bill summary: HB 2720 (2024) bill summary, Arizona House of Representatives. Signing: AZPM.

Why those changes move the economics

Certainty replaces a hearing. Before, a homeowner could spend on plans and still be denied. By-right approval means the risk is in the design and the budget, not in a vote.
No owner-occupancy rule makes the unit a real asset. A future buyer can rent either the house or the casita. That is what lets an appraiser treat the unit as income-producing and what lets lenders count its rent (see rental math).
No parking requirement unlocks typical lots. On a 6,000 to 8,000 sq ft Phoenix lot, an extra required parking space was often the thing that made a casita impossible.
1,000 square feet is a real home. A one- or two-bedroom unit with a full kitchen, not a glorified guest room, which is what rents and what appraisers can find comparables for.
Five-foot setbacks fit more lots. A detached unit can sit in the back corner where the yard is otherwise unused.

What the law does not do

Residential building, fire and health-and-safety codes
Private HOA covenants (the city cannot enforce them through the permit, but they still bind the owner)
City permits for short-term rentals; a city may require the owner to live on site to use a post-2024 ADU as a short-term rental
Exclusions near military airports and in certain airport noise zones, and on tribal land
It does not override the lot itself: utilities, sewer depth, flood zones and easements still decide what is realistic. That is what our property review checks.

The follow-up laws

2025: counties

House Bill 2928 (2025), A.R.S. § 11-810.01 applied the same framework to unincorporated county land, with a compliance deadline of January 1, 2026. Unincorporated Maricopa County (Sun City, Waddell, Wittmann, Rio Verde, New River and other county islands) is covered by the 2025 county law (A.R.S. § 11-810.01). The county adopted its ADU rules on December 10, 2025. Source: A.R.S. § 11-810.01 (accessory dwelling units; counties), added by HB 2928 (2025).

2026: pre-approved plans

SB 1529 (2025): cities must offer pre-approved plans, including ADU plans of 200, 600 and 1,000 sq ft, from July 1, 2026. A pre-approved plan shortens plan review, which is the slowest and least predictable part of the schedule. Source: SB 1529 (2025) pre-approved housing design plans, bill summary.

Phoenix went further

Phoenix had its own casita ordinance in 2023 and rewrote it for the state law with Ordinance G-7317 (Z-TA-2-24), adopted November 20, 2024. On lots over 10,000 sq ft the city allows units up to 3,000 sq ft or 10% of the lot, and either unit on the lot may be rented long-term. Sources: city staff report; rules summary with ordinance citations.

Where it applies

Every Maricopa County city above 75,000 residents: Phoenix, Mesa, Gilbert, Chandler, Glendale, Scottsdale, Peoria, Tempe, Surprise, Goodyear, Buckeye, Avondale, plus unincorporated county land under the 2025 law. Smaller towns (Queen Creek, Paradise Valley, Fountain Hills, Cave Creek, Carefree, Litchfield Park, Tolleson, El Mirage, Youngtown, Guadalupe, Wickenburg, Gila Bend) set their own ADU rules and may or may not have followed the state's lead. The city-by-city page has the list with each city's price per square foot.

This page explains the law in plain terms as of October 6, 2026; it is not legal advice. Cities amend their codes, and your lot may sit in an excluded zone (near a military airport, in an airport noise zone, or on tribal land). We confirm the current rules for your address during the property review.

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