What are the ADU and casita rules in Scottsdale, Arizona?

Ordinance 4687, adopted by the City Council on September 30, 2025, is the rulebook: it allows one attached and one detached accessory dwelling unit (ADU) on a single-family Scottsdale lot. An ADU, often called a casita in Scottsdale, is a self-contained second home with its own sleeping and bathroom space and a separate entrance. The first ADU caps at 1,000 square feet or 75% of the main home, whichever is less. A second unit caps at 500 square feet. A detached unit can sit as close as five feet to a side or rear lot line. The rule owners most often miss: if you rent the ADU, you must live on the property.

Scottsdale wrote these standards to comply with a state law (House Bill 2928) that forced larger Arizona cities to allow second units. The city then layered on its own caps for size, spacing, occupancy, and rentals. Below is what each rule means for a Scottsdale build.

How many ADUs Scottsdale allows and how big

A Scottsdale single-family lot can hold one attached and one detached ADU, with a possible third unit on large lots. Ordinance 4687 recognizes three types: an attached ADU, a detached ADU, and a restricted-affordable detached ADU. A standard lot gets the first two. A lot of one acre or larger can add the third unit when it is kept as deed-restricted affordable housing.

Size is capped by unit. The first ADU is "limited to a size of 1,000 square feet or 75% of the size of the existing main single-family residential dwelling on the same lot, whichever is less." So if your house is 1,800 square feet, 75% would be 1,350. But the 1,000-square-foot cap wins because it is smaller. Any second or third ADU is "limited to a size of 500 square feet." That smaller cap shapes how owners plan a two-unit project. You get one larger casita and one compact unit, not two full-size homes.

Scottsdale also caps occupancy, which most Valley cities do not. No more than six adults total may occupy the main home and any ADUs on the same lot combined. This is a Scottsdale-specific limit. It aims to keep a single-family lot from turning into dense rooming housing. It is worth checking against your plans if you intend to house several tenants across the units.

Scottsdale setbacks, spacing, and outdoor space

A detached Scottsdale ADU can sit five feet from a side or rear lot line, must stay ten feet from the main home, and needs its own private outdoor space. A setback is the minimum distance a structure must keep from a property line. Ordinance 4687 says a detached ADU "may not be constructed in a required front yard or side yard" but one built in the rear yard "may be constructed as close as five (5) feet to a side or rear yard." So the buildable spot is the back of the lot, pushed close to the rear fence.

Two more spacing rules apply. First, the minimum distance between an ADU and the main home or another ADU on the lot is ten feet. This is a fire and access separation, not a lot-line setback, and it can be the binding constraint on a tight lot. Second, each ADU must have private outdoor living space that is at least five feet deep and 50 square feet in area. That outdoor-space rule is unusual among Valley cities and means you cannot pack a casita wall to wall with no usable patio.

Setbacks for an attached ADU follow the underlying zoning district, since the unit is part of the main structure. Building height also follows the district maximum rather than a separate ADU height cap. Confirm your zoning district's height and yard numbers before you design, since Scottsdale's residential districts vary from compact lots to large desert parcels.

Parking, entrance, and address rules in Scottsdale

Scottsdale cannot require extra parking for an ADU, but it does require that you keep the main home's parking and give each ADU its own address. State law bars the city from requiring additional parking to accommodate an ADU, and Scottsdale follows that floor. The city's standard adds that "parking for the main single-family residential dwelling on the property shall be maintained at all times," so you cannot demolish the main home's required parking to fit the casita.

Each ADU has to read as a real, separate home. Scottsdale requires each unit to "provide a unique address and display that address in a prominent location near the entrance to the ADU." A separate exterior entrance is part of what makes the unit an ADU rather than an extra bedroom. These details also matter for emergency response and for utility metering, so plan the entrance and address early.

Scottsdale also keeps a separate Guest House category that is not an ADU. A guest house in the city code is treated as accessory space that "is not a dwelling unit or an Accessory Dwelling Unit" and cannot be rented apart from the main residence. So if you only want extra space for visiting family and never plan to rent it, a guest house may face fewer requirements than a full ADU. If you want a rentable unit, you want an ADU built to the Ordinance 4687 standards. The line between the two is whether the space can ever be leased on its own, so decide your goal before you draw plans, because converting a guest house into a rentable ADU later means meeting the full ADU code.

Renting a Scottsdale ADU: the owner-occupancy rule

Scottsdale lets you rent an ADU, but if you rent it, you must live on the property. This is the rule that separates Scottsdale from neighbors like Phoenix and Mesa. The city's standard is direct: "the property owner must reside on the premise for any ADU that is rented, leased, offered for rent or lease, or occupied as a Vacation Rental or Short-term Rental." So an off-site investor cannot buy a Scottsdale home purely to lease out a backyard casita while living elsewhere.

This owner-occupancy condition reaches both long-term and short-term rentals in Scottsdale's wording. That is stricter than the state floor. State law protects long-term renting and bars a city from requiring a relationship between the owner and the ADU tenant. Scottsdale's answer was to attach the rule to the owner living on site rather than ban renting outright. The practical result is clear. A Scottsdale ADU works well as a unit you rent while you live in the main home. It does not work as a hands-off rental for an owner who lives elsewhere. If you plan to move out later and lease the whole property, the casita rental has to stop unless a new owner-occupant lives there.

Because rental and short-term-rental rules shift over time and can be sensitive to enforcement, confirm the current ADU rental terms with the City of Scottsdale before you count on rental income. For the statewide baseline these city rules sit on top of, see our pages on Arizona's ADU requirements and which Arizona cities are required to allow ADUs.

The Jematell Homes approach

Setbacks, overlays, and ADU rules shape our design work from day one. Reach out and we will talk through how this applies to your specific lot and plan.

Sources

• City of Scottsdale: Accessory Dwelling Units (ADUs)
• City of Scottsdale: Accessory Dwelling Units FAQs
• A.R.S. 9-461.18 (Accessory dwelling units; municipalities)
• City of Scottsdale: Guest Houses and ADUs