Tempe’s City guide and June 6, 2025 Zoning Administrator Opinion describe selected ADU area, setback, and height rules. The guide also notes a later December 17, 2025 Board of Adjustment decision about two-story units; these are dated administrative sources, not a substitute for current code.
Local standards
The selected local standards are summarized in the Tempe ADU City Guide. The related source Zoning Administrator’s Opinion, June 6, 2025 states the Zoning Administrator’s dated height and setback interpretation. For a lot under one acre, the guide states an ADU area maximum of the lesser of 75% of the principal dwelling’s interior habitable floor area or 1,000 square feet. At one acre or more, the comparison uses 2,000 square feet instead. The guide’s standard side/rear distance is five feet unless the district or overlay allows less.
Confirm the applicable rule
The June 2025 opinion says detached ADU height follows the single-family district height rather than the ordinary 15-foot accessory-building limit; it also says ordinary accessory-building setbacks should not apply under its stated state-law reasoning. The City guide’s later Board of Adjustment note says a use permit is required for a two-story ADU. These statements address related but distinct questions; verify current code and the case record. Zoning measurements do not by themselves establish fire separation, building-code compliance, utility capacity, or permit approval. For shared measurement methods, see the setback and separation guide and floor-area guide.
