Arizona ADU Planning: Start with the Property, Not Just the Floor Plan
A backyard home begins with a possibility: room for family, a separate place to work toward long-term housing goals, or a smaller home alongside the main residence. The first useful step is to connect that possibility to the actual property.
For Arizona owners, that means separating three conversations: what state law requires, what the local reviewing authority needs, and what fits the site comfortably.
State rules provide a starting point
Arizona Revised Statutes §9-461.18 requires covered municipalities to allow at least one attached and one detached ADU as a permitted use where a single-family dwelling is allowed. The section applies to municipalities with more than 75,000 residents and contains exclusions, including tribal land and specified airport-related areas. It is not a blanket approval for every Arizona parcel.
The statute also preserves private-party restrictive covenants and applicable building, fire and public-health/safety requirements, subject to its stated exceptions. It separately addresses construction over current or planned public utility easements: written consent from the relevant utilities is required. Read the current state statute and its full conditions.
Our takeaway for an early design conversation: establish the property’s jurisdiction before applying a rule found in an online summary. A city parcel and an unincorporated county parcel should not be treated as interchangeable.
Local review still matters
Phoenix offers a useful local example, rather than a rule for all Arizona communities. Its ADU resource page directs owners to check zoning, lot coverage and HOA rules and to consult Planning & Development before altering their property. The page also explains that a plot/site plan remains necessary in its standard-plan process; designs marked “IN REVIEW” are not yet available. Check the City of Phoenix ADU resource page for the current status and local guidance.
A standard plan, a studio concept and a property-specific permit submission serve different purposes. Our studio’s illustrative models are not Phoenix pre-approved plans.
Bring the site into the design brief
Before a consultation, collect what you already have: the address, available survey or site information, existing building plans and any known easements. A few labeled photographs can help explain access, neighboring windows and the outdoor areas you want to preserve.
Then prepare three priorities:
Everyday use: Who will live there, and which activities need their own space?
Arrival and privacy: How should someone reach the ADU without crossing the main home’s private outdoor area?
Scope and budget: Are you comparing a selected model with a custom layout, and what site work still needs investigation?
For architectural inspiration, compare our Farmhouse and Contemporary series. Use the property planner to explore an illustrative footprint, then bring your questions to a property-specific discussion.
Planner imagery and AI exhibits are concept tools—not a survey, verified property boundary or permit determination. Paid plan downloads remain disabled while payment and fulfillment are finalized.
Contact our online studio to discuss the next step, or follow @adu_design_studio for companion design notes.
Sources reviewed October 19, 2026. This is a planning overview, not a complete statement of state, county or municipal requirements. Confirm the current rules for your parcel before committing to a design.
