Casita and ADU types we build around Tucson

How do I pick the right type?

The lot comes first, the floor plan second. A solid garage points to a conversion. An open backyard with a straight path to the sewer points to a detached casita. A narrow side yard and a parent who needs help nearby point to an attached unit.

Then decide how the space will be used. If you might lease it, build it as an ADU, not a guest house. In unincorporated Pima County, a guest house is meant for family and nonpaying guests and cannot have its own utility meter.

How many units can go on one lot?

Inside Tucson city limits, the 2024 code amendment allows two ADUs per site, with a possible third on lots over an acre when that unit is rented at affordable rates, as the city's planning administrator described it in October 2024. State law frames the pair as one attached and one detached. Oro Valley, Marana, Sahuarita and Pima County each count differently. See Can I build a casita outside Tucson city limits?.

What is the state floor for size?

• Tucson, as a city over 75,000: it must allow at least 75% of the main home's gross floor area or 1,000 sq ft, whichever is less.
• Side and rear setbacks: no more than 5 feet may be required.
• Height: no stricter than for a house in the same zone.
• Kitchen: optional; a city cannot require one or prohibit one.

Is there a junior ADU in Arizona?

No separate category exists in Arizona law. If you want to turn part of your house into its own unit, we ask the reviewing office how it will be classified before drawing anything.

As of October 2026, from A.R.S. § 9-461.18, City of Tucson Planning and Development Services, KOLD reporting (October 25, 2024) and Pima County's guest house page. Confirm the rules for your parcel.