Phoenix uses “accessory dwelling unit” for a separate living area attached to or detached from an existing home; its page also mentions names such as guest house, casita, and granny flat. The City’s online page provides a preliminary screen, not a parcel approval.
Count units and identify the zone
The Phoenix Planning and Development Department FAQ says that when a lot has no more than one single-family detached primary dwelling, two ADUs are permitted in addition to that primary unit. It says a third ADU may be permitted in certain circumstances. The page directs property owners to My Community Map to identify the zoning district and to the Phoenix Zoning Ordinance for applicable lot-coverage requirements.
The City also points owners to Maricopa County Assessor data for the official lot size and structure dimensions. Treat that as a starting record: compare it with the parcel boundary and zoning rules that apply to the project. The online summary does not list every condition for a third ADU or determine whether the property qualifies.
Check the local dwelling definition and other restrictions
The City’s definition describes an ADU as a separate, self-contained living area with its own external kitchen and ordinary dwelling amenities. The form, unit count, and lot coverage still need to match the current ordinance. The City also advises owners in a homeowners association to check their HOA rules. Such private restrictions are separate from public zoning, but they may affect the project.
What to verify for your property
Use the City’s map to confirm the zone, the County Assessor’s record to check lot information, and the current ordinance to determine permitted count and coverage. Ask Planning and Development about conditions the webpage summarizes only generally, including when a third unit may be possible. Building, fire, utility, permit, overlay, and private-document checks remain separate. Do not treat the typical two-unit screen as a universal answer for every Phoenix parcel or project form.