ADU rules in Tucson

Detached casitas allowed on any parcel in a zone that allows residential uses; up to two per parcel with one single-family dwelling. Detached ADUs may not be placed between the principal building and the front street lot line (rear or side yards only).

Casitas 'can be attached or detached from the primary residence, or they can be garage conversions' (city worksheet). UDC 6.6.2.F allows accessory buildings attached to the principal building; A.R.S. 9-461.18.A.1 requires at least one attached and one detached ADU as a permitted use.

So homes under about 867 sq ft can still add a 650 sq ft casita. Height may match the single-family maximum for the zone (generally 25 ft); overall lot coverage caps (typically 70-80% by zone) still apply.

UDC 6.6.3 contains no owner occupancy requirement, and city casita materials impose none. State law also bars requiring a familial, marital, employment, or other preexisting relationship between the owner or occupant of the home and the ADU occupant.

State law independently forbids Tucson from requiring additional parking or in-lieu fees for ADUs (A.R.S. 9-461.18.B.3).

ADUs are a permitted accessory use wherever residential uses are allowed; approval is a standard residential building permit through TDC Online (about 30 days, or a 15-day fast lane using a pre-approved Casita Model Plan). A Design Development Option application is needed only for relief from standards such as setbacks. A.R.S. 9-461.18.A.1 and I.5 require ADU approval without a public hearing, variance, or conditional use permit.

A.R.S. 9-461.18.B.1 protects use and advertisement of both units as separately leased long-term rentals; 'long-term rental' is defined in 9-461.18.I.3. No ADU-specific STR restriction appears in UDC 6.6.3 or the city's casita guidance.