I keep seeing people mention that the rules and laws around backyard ADUs (aka casita or guest house) in Arizona had changed, but I haven't really found a good article to fully explain the details. So I decided to dig into it myself, pull the actual bill text, and figure out what's real, what may be misinterpreted, who benefits, and who may not.
Two state laws passed in the last two years, one covering cities and one covering counties, and together they force nearly every city and county in Arizona to allow accessory dwelling units on single-family lots. No special permit, no public hearing, no city council vote required, if your lot qualifies, the city has to approve it. That part turned out to be true. But there's also a piece of this that a lot of people seem to be getting wrong, and it could cost someone real money if they don't catch it in time. Here's what I found.
What an ADU actually is
Before getting into the law, it's worth defining the thing. An ADU (accessory dwelling unit) is a self-contained living space on your lot, its own place to sleep, its own bathroom, and its own entrance, separate from the main house. Under Arizona's legal definition, a kitchen is allowed but not required.
That last part matters, but I want to be precise about it, because it's also the part most likely to get misread. The state statute technically only requires a place to sleep and a bathroom, a kitchen is optional at the zoning-definition level, and cities can't pass a blanket rule banning or mandating one. But that's more of a technicality than a real option. Both Phoenix's and Queen Creek's own ADU guides define an accessory dwelling unit as including a kitchen, and building code generally treats a kitchen as one of the things that makes a structure a genuinely independent living unit instead of just an extra bedroom with its own bathroom. If the plan is to rent it out long-term, budget for a kitchen. Skipping it to save money is more likely to get you a structure that doesn't function, or permit, as a real ADU.
It can be attached to your house, a fully detached building in the backyard, or a converted garage. All three count as an ADU as long as they meet that basic definition, and in the Valley, "ADU," "casita," and "guest house" are pretty much used interchangeably now.
What actually changed
House Bill 2720, the "Casita Bill," passed in 2024 and took effect January 1, 2025. It required every Arizona city with a population over 75,000 (Phoenix, Scottsdale, Mesa, Chandler, Gilbert, Tempe, Glendale, Peoria, Surprise, and a handful of others) to allow accessory dwelling units on single-family lots by right.
House Bill 2928 followed in 2025 and took effect January 1, 2026. It extended the same framework to counties, so unincorporated Maricopa County and the smaller cities that fell outside HB 2720's population threshold are now covered too. Counties had until that January 1 deadline to adopt their own compliant rules or ADUs became automatically permitted on every residential lot with no local limits at all. Maricopa County adopted its own ordinance ahead of the deadline.
What you're actually guaranteed
Under both laws, if you own a single-family lot, your city or county has to allow at least one attached ADU and one detached ADU. A few things local governments are no longer allowed to do:
They can't require you to live on the property in order to rent out the ADU (in most cases, more on that below). They can't require extra parking spaces for it. They can't force the ADU to match the architecture or materials of your main house. They can't impose side or rear setbacks greater than 5 feet in most cities. And they can't pile on costly infrastructure requirements that make the whole thing impractical.
There are size limits. In Phoenix, an ADU can't exceed 75% of the main house's floor area, and on lots up to 10,000 square feet it's capped at 1,000 square feet. Larger lots get more room, up to 3,000 square feet or 10% of the lot, whichever is smaller. Other cities have similar formulas.
One exception worth knowing: for ADUs built on or after September 14, 2024, cities and counties are allowed to require the owner to live on the property if the ADU is specifically used as a short-term rental. That doesn't apply to long-term rentals.
A handful of areas are carved out entirely: tribal land, land near military installations, high-noise zones around airports, and utility easements.
The part nobody tells you: your HOA can still say no
This is the piece that trips people up. Neither HB 2720 nor HB 2928 overrides a homeowners association's CC&Rs. The Town of Queen Creek's own planning department put it plainly in guidance to residents: the law "does not prohibit HOAs from regulating ADUs... through their CC&Rs." If your HOA's recorded covenants prohibit detached structures, additional dwelling units, or rentals, your HOA can still block your ADU regardless of what the city allows.
That means you can get full sign-off from your city's planning department, get your building permit approved, and still be violating your own HOA's rules the moment you break ground. The state law and your HOA operate as two completely separate systems, and satisfying one says nothing about the other.
This matters more in the Valley than almost anywhere else in the country, because so much of Phoenix metro growth over the last three decades happened inside HOA-governed master-planned communities. Roughly 30% of all Arizonans live under an HOA, and Phoenix metro runs well above that statewide average, more than half of metro-area residents live in an HOA community, and newer subdivisions run even higher than that. Scottsdale, Gilbert, Chandler, and Peoria all skew heavily HOA-governed.
Who should actually take advantage of this
If you own a home in an older, non-HOA neighborhood, think central Phoenix, Arcadia, Encanto-Palmcroft, older sections of Tempe or Mesa, or a rural county lot, this is a real opportunity with far fewer obstacles. If you want space for aging parents or adult kids without combining households under one roof, or a straightforward path to rental income and added property value, this is about as clean a setup as you'll find.
Investors specifically hunting for non-HOA lots to add a rental unit are in a similar spot. So are larger, established properties on bigger lots, the kind more common in older subdivisions or unincorporated county land, where there's physical room for a detached unit and no HOA board standing between the plan and the permit.
Who's going to hit a wall
Anyone in a newer, HOA-governed subdivision needs to check their CC&Rs before spending a dollar on plans, not after. That covers a lot of the Valley: most of Queen Creek, Buckeye, Surprise, Verrado, DC Ranch, and newer pockets of Gilbert, Chandler, and Scottsdale built inside master-planned communities. Plenty of those HOAs have language on the books that predates either state law and still restricts or bans detached structures and additional dwellings outright.
If you're buying a home right now specifically because you want ADU potential down the road, don't assume the state law settles it. Pull the CC&Rs before you write an offer, or ask your agent to pull them for you.
What it actually costs, and what it can earn
I'm not going to throw out a price range here, because it's genuinely all over the map. You can go the cheap route with a prefab shed or kit building that gets customized into a guest space, or you can build something closer to a full custom home in the backyard. Finish level, size, whether you're converting an existing structure or building new, and who you hire all move the number a lot, and anyone quoting you a tight range without seeing your property is guessing.
Same with income. Rent one out and it can genuinely add income and value to your property, but what it actually earns depends on the unit, the neighborhood, and how it's set up. Rather than throw out a number that may not apply to your situation, reach out and we can talk through what makes sense for your specific property.
Where this leaves you
The law genuinely opened up a real option for a lot of homeowners. It also created a very specific way to waste six figures: assuming your city's approval is the only approval you need. If you're thinking about a casita, whether for family, rental income, or resale value, the first call shouldn't be to a contractor. It should be to whoever holds your CC&Rs, and then to me, so we can look at what your specific property and HOA situation actually allow before you spend a dime on plans.
Sources: Arizona House Bill 2720 (A.R.S. § 9-461.18) | Arizona House Bill 2928 (A.R.S. § 11-810.01) | Arizona Short-Term Rental Statute (A.R.S. § 9-500.39) | Town of Queen Creek Planning & Zoning, HOA Legislative Guidance | City of Phoenix Accessory Dwelling Unit Guide | Maricopa County Planning and Zoning Commission, TA250002
