What counts as a detached casita?
In Tucson's code it is an accessory dwelling unit: a self-contained living unit on the same lot as a larger single-family home, with its own sleeping and bathroom facilities. Arizona law lets you decide whether it gets a kitchen. "Casita" is simply the name most Tucsonans use.
How big can it be inside city limits?
Tucson changed how it calculates maximum size in its October 22, 2024 amendment, which took effect November 21, 2024. Whatever the city's formula, state law sets a floor: Tucson must allow at least 75% of the main home's floor area or 1,000 sq ft, whichever is smaller. The 2021 rules had capped casitas at 10% of lot size up to 1,000 sq ft. We work from the current text for your zone.
How tall, and how close to the line?
The 2024 amendment adjusted height limits and setbacks. KOLD reported the proposal would let ADUs be as tall as the main home, up from the 12-foot limit of 2021. Under state law, Tucson cannot require more than 5 feet from a side or rear property line. Lot coverage still counts, and utility easements are off-limits without the utility's written consent.
Do I need to add parking?
No. The 2024 changes removed Tucson's minimum parking requirement for ADUs, and state law bars a city of Tucson's size from requiring added parking or a fee in its place.
Can I start from a pre-approved plan?
Yes. Tucson launched its Casita Model Plan Library in January 2024 with designs from a city competition run with AIA Southern Arizona and an AARP Community Challenge grant. The city's 2024 review counted seven pre-approved models. You buy a plan from its designer, then we adapt the site plan and build it. A model plan saves design time; a custom plan fits odd lots better.
What does a detached casita cost?
As of October 2026, a 2026 Arizona cost guide prices a 600 sq ft Tucson casita at about $90,000 basic to $250,000 high-end. Those base figures leave out caliche removal and desert-rated cooling. See the Tucson cost guide.
Where does it depend?
On lot size, sun, and how far the casita sits from the sewer and water service. A deep lot with the casita at the back means a long trench. Caliche can turn a simple footing into a slow dig. And if you are in an HOA, its rules apply on top of the city's. See the HOA guide.
Related
As of October 2026, from City of Tucson PDSD pages on the ADU code amendment and its 2024 Year in Review, KOLD (July 23 and October 25, 2024), A.R.S. § 9-461.18 and CostToBuildHouse.com.
Is there room for a casita?
Send your address. We check coverage, setbacks, easements and the sewer route before you pay for plans.