Tempe

Arizona has enacted statewide ADU preemption in two waves. HB 2720 (signed 2024-05-21, codified at A.R.S. § 9-416.18) requires every Arizona municipality with population of at least 75,000 to permit ADUs on single-family parcels by 2025-01-01: at least one attached and one detached ADU on every single-family lot, plus a third detached ADU on lots one acre or larger if at least one unit is income-restricted. HB 2928 (signed 2025-05-28) extends the same regime to counties, with a 2026-01-01 compliance deadline; counties that fail to adopt compliant regulations by that date must allow ADUs by-right on every residential parcel. Both bills cap ADU size at the lesser of 75% of the primary dwelling's gross floor area or 1,000 sqft, prohibit additional parking requirements, prohibit design-matching mandates, set a 5-foot maximum side and rear setback, prohibit additional impact fees keyed to ADU status, and forbid public-street-improvement conditions. Owner-occupancy may be required by a city or county only when the ADU is operated as a short-term or vacation rental and only for ADUs constructed on or after 2024-09-14. Critically, both bills explicitly preserve the enforceability of private CC&Rs, so HOAs may continue to ban ADUs.

Arizona does not operate an ADU-specific statewide loan, grant, or forgivable-loan program. The Arizona Department of Housing (ADOH) administers the State Housing Trust Fund, federal HOME and CDBG pass-through, the federal Low-Income Housing Tax Credit allocation, and the Arizona is Home down-payment-assistance and mortgage product line. None target ADU construction directly, though an ADU-bearing primary residence can qualify for the underlying mortgage when other eligibility criteria are met. The Arizona Industrial Development Authority issues mortgage credit certificates and revenue bonds that can flow through to ADU-bearing properties on the same basis as conventional homes.

• Arizona Department of Housing
• Arizona is Home Down Payment Assistance
• Homeowner Assistance Fund (HAF)

Arizona's state-level ADU programs work through the HB 2720 / HB 2928 preemption framework rather than through a separate pre-approved-plan catalog or fee-waiver statute. The state itself does not maintain an ADU plan library, but HB 2720 and HB 2928 effectively waive impact fees keyed to ADU status by prohibiting cities and counties from imposing them. Pre-approved plan libraries are emerging at the city level (Tempe received a 2025 AARP Community Challenge Grant for an ADU Design Challenge that will populate its standard plan library). No statewide ministerial-approval timeline mandate exists beyond the general preemption requirements; cities and counties retain discretion over the review process so long as they do not impose conditions HB 2720/2928 forbids.

• HB 2720 / HB 2928 implicit fee-waiver
• ASU Morrison Institute / Arches HB 2720 Implementation Brief