Arizona's ADU Law: HB 2720 (2024)

This page is general information for homeowners, not legal advice.

What this law does

HB 2720 makes accessory dwelling units — casitas, backyard cottages, garage apartments — legal to build on single-family lots in Arizona's larger cities. If your city has more than 75,000 residents, it can no longer ban ADUs outright, and it can't bury them under parking mandates, design-matching rules, or oversized setbacks. The law sets a floor: at least one attached and one detached ADU per single-family lot, at a size the city must accept, as permitted uses subject to the statute's approval limits.

Status

• In force. Signed by the Governor on May 21, 2024 (azleg.gov bill-status record for HB2720, 56th Legislature, 2nd Regular Session); enacted as Laws 2024, chapter 196.
• Took effect on September 14, 2024, the general effective date for laws passed in the 2024 regular session (azleg.gov General Effective Dates table: 56th Legislature, 2nd Regular Session — 09-14-2024).
• Created A.R.S. § 9-461.18 (accessory dwelling units; regulation; applicability; definitions) and amended A.R.S. § 9-500.39 (vacation rentals) (Laws 2024, ch. 196, enacting clause: "Title 9, chapter 4, article 6, Arizona Revised Statutes, is amended by adding section 9-461.18").
• Cities covered by the law had until January 1, 2025 to adopt complying ADU regulations (A.R.S. § 9-461.18(F)).
• Amended in 2025: HB 2928 (Laws 2025, ch. 217, signed May 23, 2025; effective September 26, 2025 per the azleg.gov General Effective Dates table) narrowed the airport-area exclusion — see "What it actually says" below — and added A.R.S. § 11-810.01, which requires counties to adopt ADU rules for unincorporated land. This page reflects the current, amended text of § 9-461.18.
• Last verified: September 1, 2026.

What it actually says

Who must comply. The statute applies to any municipality with a population of more than seventy-five thousand persons (A.R.S. § 9-461.18).

What cities must allow. On any lot or parcel where a single-family home is allowed, the city must allow at least one attached and one detached ADU as a permitted use (A.R.S. § 9-461.18(A)). On lots of one acre or more, the city must allow a minimum of one additional detached ADU if at least one ADU on the lot is a "restricted-affordable dwelling unit" — one rented to households earning up to eighty percent of area median income (A.R.S. § 9-461.18(A) and definitions).

Size. The city must allow an ADU that is seventy-five percent of the gross floor area of the single-family home on the same lot, or one thousand square feet, whichever is less (A.R.S. § 9-461.18(A)). "Gross floor area" means the interior habitable area (A.R.S. § 9-461.18, definitions).

What cities may NOT do (A.R.S. § 9-461.18(B)):

• Prohibit the single-family home or the ADU from being used or advertised as separately leased long-term rental housing — "long-term" meaning ninety days or longer, or month-to-month (§ 9-461.18(B) and definitions).
• Require any family, marriage, or employment relationship between the people living in the house and the people living in the ADU (§ 9-461.18(B)).
• Require additional parking for the ADU, or fees in place of parking (§ 9-461.18(B)).
• Require the ADU to match the main home's exterior design, roof pitch, or finishing materials (§ 9-461.18(B)).
• Apply stricter standards to the ADU than to single-family homes in the same zone for height, setbacks, lot size or coverage, or building frontage (§ 9-461.18(B)).
• Set rear or side setbacks for ADUs of more than five feet from the property line (§ 9-461.18(B)).
• Require public street improvements, except reconstructing what construction actually disturbed (§ 9-461.18(B)).
• Require a restrictive covenant as a condition of an ADU permit (§ 9-461.18(B), (C)).

Building codes. Cities may not require ADUs to comply with commercial building codes or to install fire sprinklers (A.R.S. § 9-461.18(D)).

Private covenants. The statute says it "does not prohibit restrictive covenants concerning accessory dwelling units entered into between private parties," while separately barring a city from requiring a restrictive covenant as a permit condition (A.R.S. § 9-461.18(B)(8), (C)). The statute itself does not decide whether a particular private covenant is valid or enforceable.

The penalty for city foot-dragging. If a covered city failed to adopt complying regulations by January 1, 2025, ADUs "shall be allowed on all lots or parcels zoned for residential use in the municipality without limits" (A.R.S. § 9-461.18(F)).

Short-term rentals. HB 2720 originally amended A.R.S. § 9-500.39 to permit an owner-residency rule for a vacation rental on property containing an ADU constructed on or after the law's effective date (Laws 2024, ch. 196, § 2). HB 2928 later replaced that construction-date trigger with a final-approval-date trigger; see the separate HB 2928 page for the current wording.

The 2025 amendment — airport areas. As originally enacted in 2024, the statute did not apply to land "in the territory in the vicinity of" an FAA commercially licensed airport, a general aviation airport, or a public airport as defined in A.R.S. § 28-8486 (Laws 2024, ch. 196). HB 2928 (Laws 2025, ch. 217) inserted "that has a noise level of greater than sixty-five decibels" after the third category in A.R.S. § 9-461.18(G)(3). Under the ordinary last-antecedent reading, that phrase modifies the public-airport category immediately before it; the text does not expressly say whether it also reaches the two earlier civil-airport categories. The exclusions for tribal land and for territory in the vicinity of a military airport or ancillary military facility (as defined in A.R.S. § 28-8461) remain, without a decibel qualifier (A.R.S. § 9-461.18(G)).

Where it applies

• Covered: municipalities with a population of more than 75,000 (A.R.S. § 9-461.18). By recent Census figures that reaches Arizona's larger cities — Phoenix, Tucson, and Mesa, for example — but see "What's still unsettled" on the exact roster.
• Not covered: smaller cities and towns (population 75,000 or under) are not required to follow § 9-461.18 (A.R.S. § 9-461.18, applicability).
• Excluded land, even in covered cities: tribal land; territory in the vicinity of a military airport or ancillary military facility (A.R.S. § 28-8461); and the civil-airport categories in A.R.S. § 9-461.18(G)(3), followed by the phrase "that has a noise level of greater than sixty-five decibels." See the unresolved grammar point below before treating that qualifier as applying to every civil-airport category.
• Counties: since 2025, a parallel statute, A.R.S. § 11-810.01 (added by Laws 2025, ch. 217), requires counties to adopt ADU rules for unincorporated land. This page covers the municipal statute; the county statute has separate standards that are not detailed here.

What's still unsettled

• Which civil-airport categories the 65-decibel phrase modifies. HB 2928 inserted the phrase after the public-airport category in § 9-461.18(G)(3), creating a last-antecedent question that the statutory text does not expressly resolve for the two earlier categories.
• How airport "vicinity" and the 65-decibel test are measured. The statute text we read does not specify a noise metric (e.g., day-night average vs. peak) or who draws the noise contour. We could not verify a mapping method from the statute itself.
• The exact roster of covered cities. The 75,000-population threshold is in the statute, but we did not verify from a primary source which cities currently cross it or which population count (decennial census vs. mid-decade estimate) governs.
• Separate sale of an ADU. The chaptered text contains no provision addressing whether an ADU may be sold separately from the main home. Confirm the current subdivision, condominium, and title requirements before treating separate sale as available.
• The § 9-500.39 owner-residency amendment. The session law's vacation-rental clause cross-references A.R.S. § 12-1134 (Arizona's private-property-rights statute) in a way we did not fully trace; treat our one-sentence summary above as a pointer, not a complete statement.
• Other 2025 changes. HB 2928 also amended A.R.S. §§ 9-500.39, 9-500.49, and 11-269.17; we did not itemize those changes here.
• Litigation. We did not verify any pending litigation over this statute one way or the other.

Related pages

• Arizona's Middle-Housing Law: HB 2721
• HB 2928 — the 2025 ADU follow-up (Laws 2025, ch. 217)

Verified-answer blog posts (HOA vs. HB 2720; ADU vs. guest house vs. short-term rental; Starter Homes Act) will be linked after the live Blog collection URL pattern is inspected. Do not invent cost-guide or permit-process slugs.

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• Chaptered session law (Laws 2024, ch. 196 / HB 2720): https://www.azleg.gov/legtext/56leg/2R/laws/0196.htm
• Current statute, A.R.S. § 9-461.18: https://www.azleg.gov/ars/9/00461-18.htm
• Bill status, HB 2720 (56th Leg., 2nd Reg. Sess.): https://apps.azleg.gov/api/Bill/?billNumber=HB2720&sessionId=128
• 2025 amendment, chaptered (Laws 2025, ch. 217 / HB 2928): https://www.azleg.gov/legtext/57leg/1R/laws/0217.htm
• Bill status, HB 2928 (57th Leg., 1st Reg. Sess.): https://apps.azleg.gov/api/Bill/?billNumber=HB2928&sessionId=129
• General effective dates (2024 = 09-14-2024; 2025 = 09-26-2025): https://www.azleg.gov/general-effective-dates/

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