What is an ADU in Phoenix?
An ADU is an attached or detached independent living area with its own living, sleeping, kitchen, and bathroom amenities. Homeowners may also call it a casita, guest house, granny flat, or backyard unit.
Phoenix ADU rules
Phoenix ADU rules in plain English
A practical homeowner guide to casitas, guest houses, garage conversions, and backyard ADUs in Phoenix. Use this to get oriented before you talk to a builder, designer, permit consultant, or lender.
Important: Rules can change. This page is an independent guide and should be verified against current City of Phoenix Planning and Development resources before you spend money.
Direct answers
Phoenix ADU rules: quick answers
Can a Phoenix lot have more than one ADU?
Phoenix says many eligible single-family lots may allow two ADUs, with a third possible in certain circumstances. Property-specific review still matters before making plans.
Do Phoenix ADUs need permits?
Yes. ADU projects generally require plans, permits, reviews, and inspections. Always verify current requirements with City of Phoenix Planning and Development before construction.
What counts as an ADU?
Phoenix describes an ADU as an independent living area, attached or detached, with living, sleeping, kitchen, and bathroom amenities. Homeowners may call it a casita, guest house, granny flat, or backyard unit.
How many may be possible?
The City of Phoenix says the newer guest house rules allow two ADUs per lot, and even three on certain lots. The specific mix can depend on the lot and project type.
How big can it be?
Phoenix says each ADU may be up to 75% of the gross floor area of the main house, with maximums tied to lot size. Lot coverage, setbacks, utilities, and building code still matter.
What usually decides whether a Phoenix ADU project is realistic?
- Zoning district and current property use
- Lot size and lot coverage limits
- Existing home size and ADU size cap
- Side, rear, street-side, and alley conditions
- Utility access, sewer, electrical capacity, and water
- Garage, parking, driveway, and access layout
- Floodplain, drainage, easements, and site constraints
- HOA restrictions, private covenants, and neighborhood rules
Good project fit
A project is easier to review when you know the property address, project goal, rough budget, and likely timeline.
Helpful next step
Start with a preliminary property check before paying for plans or requesting detailed quotes.
Official resources to verify
Before building, homeowners should review the current City of Phoenix ADU page, zoning ordinance, permit process, and any relevant property-specific requirements.
More homeowner questions
Common Phoenix ADU questions
What should I check before paying for ADU plans?
Check zoning, lot size, lot coverage, setbacks, utility access, HOA limits, budget, financing path, and whether the project goal is family housing, rental income, or guest space.
Can an ADU be detached from the main house?
ADUs can be attached or detached depending on the property and project. Detached casitas often need more site work and utility planning than attached suites or conversions.
Free homeowner check
See what your Phoenix property might support.
Answer a few questions about your ZIP code, project type, budget, and timeline. The form is designed to screen real ADU projects before sending them to a local pro.
Start the free ADU eligibility check