Rules Guide
Tucson’s Casita Law, Explained
Arizona changed the rules and most Tucson homeowners still do not know. No public hearing, no owner-occupancy requirement, and since November 2024, no additional parking space.
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Rules Guide
Arizona changed the rules and most Tucson homeowners still do not know. No public hearing, no owner-occupancy requirement, and since November 2024, no additional parking space.
The short answer
Arizona House Bill 2720, codified at A.R.S. § 9-416.18, requires cities above 75,000 people including Tucson to permit accessory dwelling units by right on lots with single-family homes. Tucson allows up to 1,000 square feet, caps rear and side setbacks at five feet, cannot require owner occupancy, and since November 21 2024 requires no additional parking. Short-term rental of an ADU is not permitted.
For years, building a casita in Tucson meant a discretionary process, a public hearing and a real chance of being refused after paying for drawings. Arizona's legislature changed that with HB 2720, which became A.R.S. § 9-416.18.
The core of it: municipalities above 75,000 population must permit accessory dwelling units by right on single-family lots. By right is the load-bearing phrase. It means ministerial review rather than discretionary approval. If the plans meet the published standards, the permit issues. There is no hearing and no neighbour veto.
Tucson adopted implementing amendments, and a further change on November 21 2024 removed the additional parking requirement.
| Standard | What Tucson allows | Notes |
|---|---|---|
| Maximum size | 1,000 sq ft, or 75% of the primary dwelling, whichever is smaller | With a minimum of 650 sq ft guaranteed for detached and attached units. |
| Rear and side setbacks | Capped at 5 ft from property lines | Front setback follows the underlying zone. |
| Height | Matches the single-family limit for the zone, generally up to 25 ft | Worth confirming for your specific parcel before designing two storeys. |
| Owner occupancy | Not required | The statute prohibits municipalities from mandating it. |
| Additional parking | None required | Changed November 21 2024. This is what opened up smaller lots. |
| Short-term rental | Not permitted | Long-term rental, family housing and accessory living space only. |
| Junior ADUs | Not currently permitted in Tucson | A converted bedroom with its own entrance does not qualify. |
The restriction that changes the maths
Tucson does not permit short-term rental of accessory dwelling units.
If your financial model depended on nightly rates, that is the constraint to know before you spend a dollar on design. A casita here is a long-term rental, family housing, a home office or guest accommodation.
The long-term rental case is still strong, precisely because owner-occupancy requirements are now prohibited. You can rent the casita, or rent the main house and live in the casita.
Three routes, and they differ enormously.
| Route | Typical Tucson cost | Notes |
|---|---|---|
| New detached construction | $145 – $290 / sq ft | 650 sq ft runs roughly $110,000–$190,000. 1,000 sq ft runs $150,000–$220,000+. |
| Garage conversion | $55,000 – $130,000 | Cheapest by a wide margin. Slab, walls and roof already exist. You lose the garage. |
| Attached casita | $130 – $260 / sq ft | Shares a wall and part of the foundation. |
| City building permit | $3,500 – $5,500 | Ministerial review, commonly 90 to 120 days. |
| Impact fees | $1,200 – $2,000 | Assessed separately from the permit. |
| Utility connections | $5,000 – $25,000 | Water and sewer trenching, electrical. An older 100-amp panel almost always needs upgrading. |
Generally no, and this is the single most common misunderstanding about HB 2720.
The statute binds municipalities. It does not void private covenants between a homeowner and an association. Many Tucson-area HOAs, particularly in Oro Valley, Marana, Dove Mountain and Rita Ranch, restrict accessory dwellings, second kitchens or rental use, and those restrictions generally still apply.
Read your CC&Rs before spending anything on design. It is the first thing we check.
It applies to municipalities above 75,000 population. That covers the City of Tucson, which includes Rita Ranch and Midvale Park.
It does not compel Oro Valley, Marana, Sahuarita or South Tucson, all of which sit below that threshold and are governed by their own zoning.
And unincorporated Pima County areas including Catalina Foothills, Tanque Verde, Vail and most of Flowing Wells follow county rules, which are not identical to the city's. Which authority governs your address is the first question on any casita project. See the permits guide.
Plan on roughly twelve to eighteen months from first conversation to certificate of occupancy for a new detached casita, and meaningfully less for a garage conversion.
Design and engineering come first. Permit review in Tucson commonly runs 90 to 120 days. Then construction. Anyone quoting materially less than that has either not accounted for review time or is working from a stock plan.
Straight Answers
In almost all cases within the City of Tucson, yes. HB 2720, codified at A.R.S. section 9-416.18, requires cities above 75,000 people to permit accessory dwelling units by right on single-family lots. That means ministerial review with no public hearing.
The practical limits are your lot's coverage allowance, your HOA's covenants, and whether your address is actually in the city or in unincorporated Pima County.
Up to 1,000 square feet, or 75 percent of the primary dwelling, whichever is smaller, with a minimum of 650 square feet guaranteed for detached and attached units.
Rear and side setbacks are capped at five feet under the state law, and height follows the single-family limit for your zone, generally up to 25 feet.
No. HB 2720 specifically prohibits municipalities from imposing owner-occupancy requirements on accessory dwelling units.
You can rent the casita, or rent the main house and live in the casita. This is the change that most improved the financial case for building one.
No. Short-term rental use of accessory dwelling units is not permitted in Tucson, even though the state law opened ADUs up in most other respects.
Casitas may be used as long-term rentals, family housing, guest accommodation or accessory living space such as a home office or studio.
No. As of November 21 2024, Tucson does not require an additional parking space for an accessory dwelling unit.
That change matters more than it sounds. Parking requirements were what made casitas impossible on many smaller midtown and older-neighbourhood lots.
It might, and the state law does not help you there. HB 2720 binds municipalities, not private covenants between homeowners and their associations.
Many Tucson-area HOAs restrict accessory dwellings, second kitchens or rental use. Read your CC&Rs before you spend money on drawings.
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