Accessory dwelling units (ADUs) and casitas are the single biggest opportunity in Arizona home improvement right now. As the state expands where and how homeowners can add a second, independent living unit, East Valley families are using them for multi-generational living, rental income, home offices, and long-term flexibility. This guide pulls together everything you need to know — the terminology, the types, the costs, the rules, and how to start.
What is an ADU — and how is it different from a casita?
An ADU is a legal designation for a complete, independent living unit on the same lot as a primary home, with its own kitchen, bathroom, and entrance. "Casita" and "guest house" are descriptive Southwest terms for a small secondary structure, which may or may not meet the full ADU definition. The short version: an ADU is a legal category; a casita is a name. A casita with a full kitchen and private entrance usually qualifies as an ADU.
The main types of ADU
- Detached ADU (casita): a standalone structure — the most private and flexible, and the most expensive to build.
- Attached ADU: an addition with its own entrance, sharing a wall with the main home.
- Garage-conversion ADU: converting an existing garage into a finished, independent unit — the most affordable path.
How much does an ADU cost in Arizona?
Costs depend most on whether you build new or convert existing space. As East Valley planning ranges:
| ADU type | Typical size | Ballpark cost |
|---|---|---|
| Garage conversion | 300–500 sq ft | $60,000 – $130,000 |
| Attached ADU | 400–700 sq ft | $110,000 – $200,000 |
| Detached ADU / casita | 500–900 sq ft | $150,000 – $300,000+ |
Arizona ADU rules and zoning
Arizona has moved to expand ADU allowances statewide, but the specifics — size caps, setbacks, parking, and owner-occupancy — still come down to your city and your lot. Before you commit to a design, it's worth a feasibility check so you build something your property actually allows and can permit. A licensed general contractor handles the plans, permits, and inspections so the unit is legal and financeable.
Do ADUs add value?
Generally, yes. An ADU adds livable square footage and a potential income stream — both of which buyers and appraisers value, especially in high-demand East Valley cities like Gilbert, Chandler, Mesa, and Queen Creek. Many homeowners treat the rental income as a way to offset the build cost over time. Actual returns depend on your lot, the finish level, and local rental demand.
How to get started
The best first step is a feasibility check on your specific lot: what your zoning allows, where the unit can sit, and how utilities will reach it. From there, design, permitting, and construction follow. We manage the entire process end to end, with a fixed price and one accountable team — so your ADU is comfortable, code-compliant, and built for the Arizona climate.
Related services & areas
Planning a project in Gilbert or the East Valley?
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