Arizona ADU Rules

Backyard housing isn’t going anywhere in Arizona. But a recent attempt to rewrite the rules won’t move forward this session. That's today's topic for LUXE BLOG. Enjoy.

State lawmakers considered adjustments to the 2024 accessory dwelling unit law that reshaped zoning in larger cities across Greater Phoenix & beyond. The proposal would have expanded size limits and shifted how cities handle setbacks and design rules. Instead, the current framework remains in place. For now, homeowners and cities operate under the same statewide standards adopted last year.

Quick Points

• Lawmakers declined changes to 2024 ADU law.

• Proposal targeted size limits & setbacks.

• Current rules already rank among most permissive.

• Cities over 75,000 must allow ADUs.

• Existing framework remains unchanged.

Also Read: World War Casita – Scottsdale Challenges The State’s New Law

What Lawmakers Wanted To Change

The recent proposal sought to loosen several of those standards.

First, it would have removed the 1,000 square foot ceiling on ADUs. The 75% size limit tied to the main home would have remained. In practical terms, larger primary homes could have supported significantly larger secondary units.

The measure also addressed how close ADUs could sit to property lines. Current law prevents cities from requiring setbacks greater than five feet. The proposal would have lifted that restriction, giving cities more discretion over lot line placement.

It also would have reduced city authority over certain exterior design elements, including elevation.

Proposed shifts included:

• Eliminate 1,000 square foot limit

• Keep 75% size threshold

• Adjust setback authority

• Limit design oversight

Supporters connected these changes to housing supply pressures and rising costs. Opponents, including homeowners and municipal representatives, argued the existing law already struck a balance.

Also Read: The Post-Pandemic Casita & Guest House Trend Explained

The 2024 Law Already Changed The Game

Arizona’s ADU policy did not arrive overnight. Lawmakers spent nearly two years negotiating before passing the 2024 measure. The law requires cities with populations above 75,000 to allow homeowners to build one attached unit and one detached unit on a single lot.

Cities across “The Valley” then updated zoning codes. Many had to revise long-standing restrictions. Backyard units became a statewide mandate in larger municipalities.

Here’s what current law allows:

• One attached ADU

• One detached ADU

• Up to three units on one-acre lots

• Five-foot maximum setback requirement

• 1,000 square foot cap or 75% rule

That framework already places Arizona among the more flexible ADU states, according to the League of Arizona Cities & Towns.

A Close Committee Decision Ends The Push

In the end, the proposal did not advance out of the House Appropriations Committee. The vote was narrow, but enough to halt the bill.

That outcome leaves the 2024 ADU law intact. Cities continue operating under the statewide mandate. Homeowners in larger municipalities still have the right to build attached and detached units within current size and setback limits.

Housing policy in the Arizona real estate market continues to shift. For now, though, the state’s ADU rules remain exactly where lawmakers placed them last year.