Tempe, AZ Accessory Structures: ADU Rules (2026)

Section 3-402 of Tempe's Zoning and Development Code permits accessory dwelling units in every residential district on a lot with a single-family dwelling. Density is capped at one attached ADU and one detached ADU on any lot under one acre; a lot of one acre or more can add a third ADU if one of the three is designated a restricted-affordable dwelling unit under Section 3-402(G). Size is limited to 1,000 square feet of interior habitable area, or 75 percent of the main residence's gross floor area, whichever is less, on lots under an acre; on lots of an acre or more the cap rises to 2,000 square feet under the same 75-percent test. An ADU capped at 1,000 square feet may have no more than three bedrooms, while larger-lot ADUs have no bedroom limit.

Setbacks for both attached and detached ADUs are a minimum of five feet from the rear, side and street-side lot lines in every district, though a detached ADU can use the smaller accessory-building setback under Section 3-401 where that standard allows less. Front-yard setback follows the standard district setback table in Section 4-202. ADU height follows the same limit as the underlying district's single-family height standard, and the ADU's building footprint counts toward the lot's overall maximum lot coverage. No additional off-street parking is required for an ADU. Each ADU must be separately addressed with its own house number near its entrance, and it must have its own kitchen, bathroom and sleeping facilities connected to city sewer, water and utility service.