Can I build an ADU on a single-family lot in Arizona?

In cities with at least 75,000 residents, yes: Arizona's 2024 HB 2720 requires those cities to permit ADUs by right on qualifying single-family lots, and any city that missed the January 1, 2025 compliance deadline lost the ability to restrict ADUs at all. In smaller cities and unincorporated county land, ADU rules still depend on the local zoning ordinance.

What is Arizona's 'missing middle' housing law?

HB 2721, passed in 2024, requires Arizona's largest cities to allow duplex, triplex, and fourplex housing — and larger buildings near transit — on lots that were previously zoned exclusively for single-family homes, with a compliance deadline running into 2026. It works alongside HB 2720's ADU mandate to add by-right density in the state's biggest housing markets.

How do I look up zoning for a parcel in Arizona?

Zoning is set at the city or county level, so start with the relevant municipal planning department, or the county assessor or planning office for unincorporated land, for a parcel's current district and any pending rezoning. The AZGeo Data Hub and the Arizona State Land Department's parcel viewer aggregate some statewide GIS layers, but zoning-district boundaries themselves are maintained locally.

Do Arizona counties zone the same way as cities?

No — counties zone unincorporated land under a separate enabling statute (Ariz. Rev. Stat. §§ 11-801 to 11-830) from the one cities use (§§ 9-461 to 9-470), and Arizona's 2024 ADU and middle-housing mandates apply only to municipalities above the population threshold, not to county zoning of unincorporated land.

Arizona · state zoning reference · Parcel data · lookup only

Arizona zoning: how it works and what you can build

Arizona pairs a traditional Dillon's-rule zoning-enabling framework with two of the most aggressive state housing-preemption laws passed anywhere in 2024 — mandatory ADUs and 'missing middle' housing in the state's largest cities — making it one of the fastest-moving zoning environments for developers to track.

How zoning works in Arizona

Zoning authority in Arizona flows from state enabling statutes rather than general home rule: municipalities zone under Title 9 of the Arizona Revised Statutes and counties zone unincorporated land under the parallel Title 11 framework, regardless of whether a city has adopted a home-rule charter for other governance purposes. Both frameworks follow the standard enabling-act structure — a planning and zoning commission, a general plan, and public-hearing procedures for rezonings and text amendments.

Arizona broke from that traditional pattern in 2024 with two sweeping state preemption laws. House Bill 2720 required every city with at least 75,000 residents to legalize accessory dwelling units on single-family lots by ordinance; cities that missed the January 1, 2025 compliance deadline lost the ability to restrict ADUs at all, with by-right ADUs then applying on any residentially zoned lot statewide in that jurisdiction. House Bill 2721, the companion 'middle housing' bill, requires those same large cities to allow duplexes through fourplexes — and larger structures near transit — on lots previously zoned exclusively single-family, with a compliance deadline running into 2026.

For developers, the practical effect is that Arizona's largest cities — Phoenix, Tucson, Mesa, Scottsdale, Chandler, and Gilbert — are mid-transition: legacy Euclidean zoning ordinances are being amended in real time to comply with HB 2720 and HB 2721, so the same parcel can carry materially different by-right entitlement today than it did in 2023. Smaller cities under the 75,000-population threshold, and unincorporated county land under Title 11, are unaffected by either mandate and retain conventional local control.

Who holds the zoning power

Land-use authority in Arizona is delegated by statute, not assumed — these are the acts a zoning ordinance in Arizona has to trace back to.

Municipal Zoning Enabling Act Ariz. Rev. Stat. §§ 9-461 to 9-470: Authorizes cities and towns to adopt general plans and zoning ordinances, including overlay districts.
County Zoning Enabling Act Ariz. Rev. Stat. §§ 11-801 to 11-830: Parallel enabling authority for county zoning of unincorporated land.
Accessory Dwelling Unit Mandate H.B. 2720 (2024), 56th Legislature, 2nd Regular Session: Requires cities of 75,000+ population to legalize ADUs by right; noncompliant cities lost local ADU restrictions after January 1, 2025.
Middle Housing Mandate H.B. 2721 (2024), 56th Legislature, 2nd Regular Session: Requires large cities to allow duplex-through-fourplex 'missing middle' housing on former single-family lots.

Major cities and their codes

The enabling act sets the ceiling; the municipal code is what a project is actually reviewed against. The 6 largest Arizona jurisdictions and the codes they administer:

Arizona — municipal zoning codes
City	Zoning code
Phoenix	Phoenix Zoning Ordinance Arizona's largest city; ordinance being amended to comply with the 2024 statewide ADU and middle-housing mandates.
Tucson	Tucson Unified Development Code Consolidated zoning and subdivision code; second-largest city, subject to the same 75,000-population state mandates.
Mesa	Mesa Zoning Ordinance Already permits accessory dwelling units by right in single-residence districts ahead of the statewide mandate.
Scottsdale	City of Scottsdale Zoning Ordinance High-value resort and residential market with extensive planned-unit-development and hillside-overlay zoning.
Chandler	Chandler Zoning Code East Valley technology and manufacturing corridor city, subject to the 2024 state ADU and middle-housing mandates.
Gilbert	Gilbert Land Development Code One of the fastest-growing large towns in the Phoenix metro; general-plan-driven zoning.

Recent reforms

State-level changes override or preempt what a local ordinance says — these are the Arizona reforms that move the numbers on a real site.

2024 HB 2720 (Accessory Dwelling Unit Mandate) Requires Arizona cities of 75,000+ residents to legalize ADUs by right, with noncompliant cities losing local ADU restrictions after January 1, 2025.
2024 HB 2721 (Middle Housing Mandate) Requires large Arizona cities to allow duplex-through-fourplex housing on former single-family lots, with compliance running into 2026.

Parcel & GIS data

Arizona maintains one of the more mature statewide GIS clearinghouses among the states covered here — the AZGeo Data Hub, built jointly by the Arizona State Land Department and the Arizona Geographic Information Council — though authoritative parcel and zoning-district data still originate at the county-assessor and municipal level.

Real parcel geometry is already loaded for Phoenix and Tucson — see the zoning-by-city section above for a live district-and-parcel lookup there. That is not the same as a cited feasibility report: Chicago is still the only jurisdiction with bulk standards, § citations and a generated massing scheme.

Zoning by city

The statute sets who may zone; the city's own code sets what you can build. One guide per Arizona city below, explaining the district codes that appear on its zoning map — 68 district codes across Arizona so far.

Arizona zoning — common questions

Can I build an ADU on a single-family lot in Arizona?: In cities with at least 75,000 residents, yes: Arizona's 2024 HB 2720 requires those cities to permit ADUs by right on qualifying single-family lots, and any city that missed the January 1, 2025 compliance deadline lost the ability to restrict ADUs at all. In smaller cities and unincorporated county land, ADU rules still depend on the local zoning ordinance.
What is Arizona's 'missing middle' housing law?: HB 2721, passed in 2024, requires Arizona's largest cities to allow duplex, triplex, and fourplex housing — and larger buildings near transit — on lots that were previously zoned exclusively for single-family homes, with a compliance deadline running into 2026. It works alongside HB 2720's ADU mandate to add by-right density in the state's biggest housing markets.
How do I look up zoning for a parcel in Arizona?: Zoning is set at the city or county level, so start with the relevant municipal planning department, or the county assessor or planning office for unincorporated land, for a parcel's current district and any pending rezoning. The AZGeo Data Hub and the Arizona State Land Department's parcel viewer aggregate some statewide GIS layers, but zoning-district boundaries themselves are maintained locally.
Do Arizona counties zone the same way as cities?: No — counties zone unincorporated land under a separate enabling statute (Ariz. Rev. Stat. §§ 11-801 to 11-830) from the one cities use (§§ 9-461 to 9-470), and Arizona's 2024 ADU and middle-housing mandates apply only to municipalities above the population threshold, not to county zoning of unincorporated land.

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The parcel layer lands in the order demand does. Illinois went first because that's where the deals were; the next state is decided by who tells us what they're trying to underwrite. Tell us where you're building and what you wanted to run — you'll hear from us when Arizona opens, and sooner if we need a test parcel.

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Want to see the finished shape of this work? Illinois is live at parcel level — Illinois zoning and the 53-district Chicago reference.

Arizona zoning summaries on this page are provided for information, not legal advice. Confirm every project against the current adopted code for the jurisdiction and the statute as amended.