Tempe, AZ Accessory Structures: ADU Permits (2026)

Arizona HB 2720, codified at ARS 9-461.18, requires Tempe to allow accessory dwelling units (casitas) by right on every lot zoned for single-family residential use. Tempe's Zoning and Development Code (ZDC) governs ADU standards consistent with the state mandate effective January 1, 2025. The state statute requires the city to allow at least one attached or internal ADU and one detached ADU per single-family lot as a permitted use without discretionary review; lots one acre or larger qualify for a third detached ADU if at least one unit is deed restricted as affordable. Setbacks for rear and interior side yards are capped at no more than 5 feet under the statute. Tempe Community Development processes applications through its online permitting portal. Required permits include building, electrical, plumbing, and mechanical, with work subject to the International Residential Code as adopted by Tempe City Code Chapter 8. Plan review typically runs two to six weeks for a standard residential ADU. Tempe's location adjacent to Arizona State University makes ADUs especially common for student housing, multigenerational living, and supplemental rental income.