HB 2928 / Laws 2025, ch. 217
In force
CURRENT STATUS
/ ARIZONA BUILDING LAW
HB 2928 is the 2025 clean-up of Arizona's 2024 casita law. It did four things that matter to a homeowner. It inserted a 65-decibel qualifier after the civil-airport exclusions, with the grammatical reach of that phrase still unsettled. It extended the ADU mandate to counties for unincorporated land. It changed the trigger for the rule that lets a city or county require you to live on the property if you rent an ADU as a short-term rental. And it exempted historic districts from a separate law on administrative plan review. It did not lower the 75,000-population line for cities.
/ LAW RECORD
In force
CURRENT STATUSSeptember 26, 2025
EFFECTIVE DATEhttps://www.azleg.gov/legtext/57leg/1R/laws/0217.htm
PRIMARY SOURCE URLThis page is general information for homeowners, not legal advice.
HB 2928 is the 2025 clean-up of Arizona's 2024 casita law. It did four things that matter to a homeowner. It inserted a 65-decibel qualifier after the civil-airport exclusions, with the grammatical reach of that phrase still unsettled. It extended the ADU mandate to counties for unincorporated land. It changed the trigger for the rule that lets a city or county require you to live on the property if you rent an ADU as a short-term rental. And it exempted historic districts from a separate law on administrative plan review. It did not lower the 75,000-population line for cities.
1. Airport zones near cities (A.R.S. § 9-461.18(G)). Before HB 2928, the city ADU mandate 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 under A.R.S. § 28-8486. HB 2928 inserted the phrase "that has a noise level of greater than sixty-five decibels" after the third category in § 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 the qualifier also reaches the two earlier civil-airport categories. Tribal land and land near military airports remain excluded without a decibel test (§ 9-461.18(G)(1)–(2)).
2. The 75,000 line did not move. The chaptered text struck "with a population of more than seventy-five thousand persons" from subsection (A) and re-inserted the same words as a new subsection (H): "This section applies to a municipality with a population of more than seventy-five thousand persons." Cities and towns at or under 75,000 are still outside § 9-461.18.
3. Counties now have their own ADU mandate (new A.R.S. § 11-810.01). "A county shall adopt regulations that allow on any lot or parcel where a single-family dwelling is allowed both of the following: 1. At least one attached and one detached accessory dwelling unit as a permitted use. 2. A minimum of one additional detached accessory dwelling unit as a permitted use on a lot or parcel that is one acre or more in size" (§ 11-810.01(A)). The county "may require at least one accessory dwelling unit on the lot or parcel to be a restricted-affordable dwelling unit" for that third unit (§ 11-810.01(A)(2)). Size: "at least seventy-five percent of the gross floor area of the single-family dwelling on the same lot or parcel or one thousand square feet, whichever is less," and a county may allow larger (§ 11-810.01(B)). The county prohibitions in subsection (C) mirror the city list: no ban on separate long-term rental, no relationship test, no added parking, no design-matching, no stricter height/setback/coverage rules than the main house, no rear or side setback over five feet, no street-improvement condition, no required covenant. Counties may still enforce "sensitive environmental area regulations, wildfire prevention regulations, emergency vehicle access regulations, drainage and flood control regulations" (§ 11-810.01(E)) and may require an adequately sized septic system where sewer is unavailable (§ 11-810.01(I)). Deadline: January 1, 2026, after which ADUs "shall be allowed on all lots or parcels zoned for residential use in the county without limits" (§ 11-810.01(G)). There is no population threshold in the county section as enacted.
4. Short-term rentals in an ADU: the owner-residency trigger changed (A.R.S. § 9-500.39(B)(9) and § 11-269.17(B)(9)). Cities and counties generally may not prohibit short-term rentals (§ 9-500.39(A); § 11-269.17(A)), but each may require the owner "to reside on the property if the property contains an accessory dwelling unit." HB 2928 rewrote the trigger. The old text keyed on an ADU "that was constructed on or after" the 2024 law's effective date. The new text keys on paperwork: the residency rule may apply only "if a certificate of occupancy, certificate of completion or similar final approval for the accessory dwelling unit was issued by the municipality on or after September 14, 2024," and "does not apply" where that final approval "was issued on or before September 13, 2024" (§ 9-500.39(B)(9); county wording identical with "county" in § 11-269.17(B)(9)). HB 2928 also added the county-side ADU definition cross-reference to § 11-810.01 (§ 11-269.17(L)(1)).
5. Historic districts and administrative review (A.R.S. § 9-500.49(D)). A separate 2025 law requires cities to let staff approve site plans, plats, and objective design review without a public hearing and lets cities adopt self-certification programs. HB 2928 added a new subsection (D): that section "does not apply to" land in a district of historical significance under § 9-462.01(A)(10), land "designated as historic on the national register of historic places," or land "designated historic by a local government." This is an exemption from the administrative-review statute. It is not an exemption from the ADU law or the middle-housing law; the 2026 bill that would have done that (HB 2375) died.
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