How to Get an ADU Permit in Phoenix, Arizona

Accessory dwelling units — ADUs, casitas, guest houses, call them what you want — are one of the most popular projects we see right now in the Phoenix area. Homeowners want the flexibility: a space for family, a rental income stream, or just extra room that actually functions as a separate living area. If you're thinking about building one in Phoenix, here's what the permitting process actually looks like and what you need to know before you start.

What Counts as an ADU in Phoenix?

An ADU is a separate, self-contained living unit on the same lot as a primary single-family home. To qualify, it needs to function independently — that means its own kitchen (with a sink, cooking appliance, and refrigeration), bathroom, living space, and sleeping area. It can be either detached (a standalone structure in the backyard) or attached to the main house.

Phoenix allows up to two ADUs on a single-family lot. In most cases, that means one attached and one detached. A third ADU is possible under specific circumstances — namely, if at least one of the units qualifies as affordable housing and the lot is at least 43,560 square feet.

Size and Setback Rules

Size limits

Each ADU can be up to 75% of the gross floor area of the primary dwelling. However, there are hard caps depending on lot size:

• Lots up to 10,000 square feet: maximum 1,000 sf per ADU

• Lots over 10,000 square feet: maximum 3,000 sf per ADU

Setbacks

For detached ADUs, Phoenix allows placement within the required rear or side yards — but not the front yard. Height for a detached ADU located in those rear or side yard areas is capped at 15 feet. If you want to go taller, a special use permit is required.

Attached ADUs follow the same setback rules as the primary dwelling unit. And under Arizona state law, local jurisdictions can't require setbacks greater than five feet for ADUs, so Phoenix is bound by that too.

Parking

On lots up to 10,000 square feet, Phoenix generally requires one off-street parking space per ADU. Properties near transit corridors may qualify for exceptions — it depends on the specific location and zone. This is worth confirming early if parking is tight on your lot.

The Permitting Process: Two Steps Before You Break Ground

ADUs in Phoenix go through a two-step approval process before construction can begin. A lot of people don't realize there are two separate stages — they try to jump straight to the building permit and get sent back to start. Here's how it actually works.

Step 1: Site Planning Approval

Before you can submit for a building permit, you need site planning approval from the City of Phoenix Planning and Development Department. This is where the city reviews your project for zoning compliance — confirming that the ADU is allowed on your specific property, that the size and placement meet code, and that the lot can accommodate it.

Don't skip or rush this step. Without site planning approval, your permit application won't move forward. Get this handled first.

Step 2: Building Permit Submittal

Once site planning is approved, you can move into the building permit process. Plans are submitted through the city's new online portal, SHAPE PHX, at shapephx.phoenix.gov. Your submittal will need to include a site/plot plan and construction drawings that cover the full scope of the project — architectural, structural, and MEP as applicable.

From there, the city's plan examiners review for code compliance, and any comments come back through the portal. Once review is complete and any corrections are addressed, the permit is issued and you can start building.

Inspections

Once the permit is issued, construction needs to be inspected at each required stage. In Phoenix, inspections are scheduled by calling 602-495-0800. A final inspection is required at project completion before the ADU is considered finished and occupiable. Don't skip intermediate inspections thinking you can just call for final — each stage has to be cleared in order.

A Few Things That Slow ADU Projects Down

The site planning step is the most common source of delay we see. When people don't know it's required, they lose weeks finding out. The other frequent issue is a site plan that doesn't accurately reflect property lines, existing structures, easements, or utility locations — that generates comments that require revision and send the project back in the queue.

Utility connections for water, sewer, and electricity also need to be addressed as part of the project. If your property doesn't already have the capacity or routing to serve a second unit, that conversation needs to happen early — not after the permit is issued.

Thinking About an ADU in Phoenix? Talk to Us First.

At SOKO Designs, we do a lot of ADU and casita work throughout the Phoenix area. We know the two-step process, we know what site planning needs to see, and we build our permit documents to get through review without a lot of back-and-forth. Getting the plans right upfront is always faster and cheaper than revising them after the city sends comments.

If you're thinking about an ADU and want to talk through the project before you commit, give us a call at 480-710-4866 or START A PROJECT NOW. We're happy to answer questions and help you figure out what's realistic for your property.

For the most current requirements, always verify directly with the City of Phoenix Planning and Development Department at 602-262-7811 or visit phoenix.gov/pdd. Regulations and processes are subject to change.