Start with one question: who issues your permit?
A Tucson mailing address doesn't mean your lot is in the City of Tucson. Big parts of the metro, including the Catalina Foothills, Casas Adobes, Tanque Verde and much of Vail, are unincorporated Pima County. Oro Valley, Marana and Sahuarita are separate towns with their own codes. Your casita follows the rules of whichever one your lot sits in, and the rules are not the same.
The quickest way to check is your parcel record on the Pima County Assessor site, or simply ask us. We confirm the jurisdiction before anything is designed.
What Arizona's 2024 casita law changed in Tucson
In 2024 Arizona passed HB 2720, which made cities with more than 75,000 people allow accessory dwelling units (ADUs, or casitas) on single-family lots. Tucson is one of those cities. The City of Tucson adopted its updated ADU rules on October 22, 2024, and they took effect on November 21, 2024. Under the state law, a city like Tucson has to:
- Allow at least one attached and one detached casita on a lot zoned for a single-family home. A second detached unit is possible on lots of an acre or more when one unit is a restricted affordable unit.
- Allow a casita up to 75% of the main home's floor area or 1,000 sq ft, whichever is smaller.
- Keep side and rear setbacks to no more than 5 feet.
- Not require extra parking for the casita.
- Allow the casita to be rented long term. If a casita built after the law is used as a short-term rental, the owner has to live on the property.
Height, lot coverage and design details still come from the city's own zoning code, and the city requires a cool roof on newly built ADUs. See the City of Tucson ADU page for the current standards. We check them against your lot at the first visit.
Pima County, Oro Valley, Marana and Sahuarita
The state law above applies to cities over 75,000 people. Unincorporated Pima County and the smaller towns set their own rules.
Unincorporated Pima County calls a detached casita a guest house. Per Pima County's guest house rules: one guest house per lot, the lot must be at least 4,000 sq ft, it may have a kitchen, it must share the main home's driveway and access, it can't have its own utility meter, setbacks follow the accessory building standards for your zone, and it's meant for family members and non-paying guests rather than paying tenants.
Oro Valley, Marana and Sahuarita each have their own code and permit office, and many neighborhoods there also have an HOA with an architectural review step. HOA approval usually comes before the town permit, so we build that into the schedule.
Tucson's pre-approved casita plans
The City of Tucson selected nine pre-approved casita designs for its Casita Model Plan Library in late 2024. Starting from one of those plans can save design time. You still need a site plan, a permit and a licensed contractor to build it. We can build from a library plan or from your own custom drawings.
Attached addition or detached casita?
An attached addition shares a wall, roof and often the HVAC with your home. It is usually simpler for utilities and works well for a primary suite or a parent's bedroom with a bath. A detached casita gives real privacy for guests, family or a long-term tenant, but it needs its own foundation, roof and utility runs. Our home addition cost guide and casita cost guide cover how each choice affects price.
What catches people out in Tucson
- Caliche. The hard layer under a lot of Tucson soil can slow digging and add foundation cost. It is worth knowing early.
- Utility distance. The farther the casita sits from your sewer line, water and electric panel, the more trenching it takes. An older panel may need an upgrade.
- Septic lots. In county areas on septic, adding a bedroom can mean the system has to be checked or enlarged before a permit is issued.
- Washes and floodplains. Lots near a wash may need a floodplain review, which affects where the casita can go.
- HOA rules. CC&Rs can limit height, materials and colors even where the town or city allows a casita.
- Matching the house. Stucco texture, paint and roof material should match so the casita looks original. We handle stucco and roofing in house, which makes that easier.
How we build a casita, step by step
- Site walk. We look at the lot, confirm who issues the permit, and talk through size, layout and budget.
- Plans. A library plan or custom drawings, plus the site plan the permit office needs.
- Permit. We prepare and submit, and answer any review comments.
- Build. Foundation, framing, structural work, roofing, stucco and interiors, with one licensed team (AZ ROC #344537).
- Inspections and final. We schedule the inspections and walk the finished space with you.