Phoenix has become one of Arizona's more landlord-friendly cities for accessory dwelling unit development, backed by state law that prevents cities from banning ADUs outright and a local ordinance that spells out exactly what you can build. An accessory dwelling unit (ADU) is a secondary housing unit on the same lot as a primary residence. These smaller units go by many names: granny flat, in-law suite, backyard cottage, carriage house. Landlords and homeowners build them to add rental income, house family members, or increase long-term property value. Here's what Phoenix law actually requires, with the specific numbers you need before breaking ground.
The legal foundation: state law and Phoenix ordinances
Arizona ARS 9-462.01 prohibits cities from banning ADUs as a blanket policy. Phoenix had to open its zoning accordingly, and the city did so through Zoning Ordinance Section 706, which allows ADUs in single-family residential zones across most of the city. A handful of zones, including RE-43, RE-24, RE-35, and R1-14, carry different rules, so checking your specific zoning district before drawing up plans is a necessary first step.
Arizona also eliminated the owner-occupancy requirement statewide in 2023. You don't have to live on the property to build or rent an ADU, which makes Phoenix a genuinely accessible market for investors and remote landlords.
Size limits: the exact numbers
Phoenix ties ADU size to lot area:
- Lots up to 10,000 sq ft: ADU maximum is 1,000 square feet
- Lots over 10,000 sq ft: ADU maximum is 3,000 sq ft or 10% of the net lot area, whichever is smaller
- No ADU may exceed 75% of the primary dwelling's gross floor area, regardless of lot size
Only one ADU is permitted per single-family lot. The unit must function as a self-contained living space, meaning it needs a kitchen (sink, cooking facility, and refrigeration), bathroom, living area, and sleeping quarters. Separate utility connections for water, sewer, and electricity are required, and no installation can infringe on public rights-of-way.
Setbacks and height limits
Setbacks in Phoenix follow the underlying zoning district rather than a single citywide number. Front setbacks keep the ADU from sitting too close to the street; rear and side setbacks vary by zone and protect neighboring privacy. Height limits are also district-specific but generally keep the ADU visually subordinate to the main house.
The City of Phoenix Planning and Development department publishes setback requirements by district. Looking up your parcel before hiring a designer will save you from plans that can't be approved. In historic districts, compatibility standards for materials, color, and architectural style are stricter, and proposals there receive additional design review before approval.
Lot coverage and zoning rules
An ADU counts toward your lot's total building coverage. Phoenix zoning ordinances set the maximum percentage of a lot that structures can cover, and recent updates to guest house rules added 10% of property coverage in most zones, giving property owners a bit more flexibility. Verifying your lot's coverage limits before finalizing plans is worth doing early, since exceeding them requires a variance that adds time and cost.
ADU designs are generally expected to complement the primary structure in materials and style. In most zones this is a guideline; in historic districts it's a firm requirement with enforceable review.
Parking requirements
On lots up to 10,000 square feet, Phoenix typically requires at least one off-street parking space per ADU. Properties near transit corridors may qualify for exceptions, and the city considers proximity to public transportation when reviewing applications. Parking rules can vary by zone, so confirming the requirement for your specific parcel with Planning and Development before submitting plans is advisable.
Permitting process step by step
Getting a permit in Phoenix follows a defined sequence. Knowing it in advance helps you plan your timeline and budget realistically.
- Prepare a site plan showing the ADU's size, location on the lot, and planned utilities, all meeting Phoenix zoning requirements.
- Submit for review through the Shape Phoenix online portal or in person at Phoenix City Hall.
- Plan review: city staff check for compliance with building codes and zoning ordinances. Revisions are common, so build time for at least one resubmission into your schedule.
- Permit issuance: once approved, construction can begin.
- Inspections happen at set stages of construction to confirm the work matches the approved plans.
- Certificate of Occupancy: after a final inspection confirms the ADU is safe and code-compliant, the city issues a certificate and the unit is legal to occupy.
Approval timelines vary depending on plan completeness and city workload. Simple projects with clean submissions have moved through in a few weeks; more complex plans or resubmissions can stretch to several months. Submitting a thorough, accurate application the first time is the single most effective way to shorten the timeline.
Fees and impact costs
Phoenix levies impact fees on new ADUs to offset the added demand on roads, parks, and water infrastructure. The fee amount depends on the ADU's size and your location within the city. Getting that figure from Planning and Development early in your budget process prevents surprises. Standard building permit fees also apply, calculated based on construction value.
The city encourages energy-efficient construction and low-impact design, but sustainability features beyond standard building code requirements aren't mandated for most ADU projects.
Rental rules and short-term rental restrictions
Phoenix does not require owner-occupancy, consistent with Arizona's 2023 statewide change. You can rent the ADU as a long-term unit without living on the property. Short-term rentals are a different matter: Phoenix restricts ADUs from operating as short-term rentals through platforms like Airbnb, even though the primary dwelling on the same lot is not subject to the same restriction.
If you're renting the ADU as a long-term investment, understanding your insurance exposure matters. A standard homeowner's policy won't cover rental activity the way a dedicated landlord policy does. You can compare options for Arizona rental properties at Steadily's Arizona landlord insurance page.
Safety and building code requirements
ADUs must meet the International Residential Code (IRC), which covers smoke detectors in sleeping and living areas, fire-resistant construction materials, and unobstructed emergency access paths. These aren't optional: inspectors check for compliance at each stage of construction, and a final inspection before the Certificate of Occupancy confirms everything meets code.
Frequently asked questions
What is the maximum ADU size allowed in Phoenix?
On lots up to 10,000 sq ft, the cap is 1,000 sq ft. On larger lots, it's 3,000 sq ft or 10% of the net lot area, whichever is smaller. In either case, the ADU can't exceed 75% of the primary dwelling's gross floor area.
Do I have to live on the property to build an ADU in Phoenix?
No. Arizona eliminated owner-occupancy requirements statewide in 2023, so you can build and rent an ADU without living on the lot.
Can I use a Phoenix ADU as a short-term rental?
No. Phoenix prohibits ADUs from operating as short-term rentals. Long-term leases are permitted.
How do I submit an ADU permit application in Phoenix?
Submit through the Shape Phoenix online portal or in person at Phoenix City Hall. You'll need a site plan and construction drawings that meet zoning and building code requirements.
How do Phoenix ADU rules differ from Maricopa County?
Phoenix operates under its own city ordinances, specifically Zoning Ordinance Section 706. Properties in unincorporated Maricopa County fall under county rules, which can differ on size limits, setbacks, and permitting procedures. If your property is outside Phoenix city limits, verify the requirements directly with Maricopa County.
Are there extra requirements for ADUs in Phoenix historic districts?
Yes. Historic districts require ADUs to match the architectural style, materials, and scale of the surrounding neighborhood. Applications in those areas go through additional design review before approval, which adds time to the permitting process.
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