What counts as an ADU
An accessory dwelling unit (ADU) is a secondary, independently livable structure on the same lot as a primary home—a detached guest house, a garage conversion, or an attached unit with its own entrance. Guest houses without a kitchen are typically treated differently by code than a full ADU with kitchen and bathroom facilities, so which one you're building matters for permitting.
Why ADU rules vary so much by location
ADU regulations—whether they're allowed at all, minimum lot size, maximum square footage, parking requirements, and whether the unit can be rented—are set at the city or county level and vary significantly. Some jurisdictions have streamlined ADU approval in recent years; others still restrict them. This is one of the first things we confirm once we know your ZIP code.
What's typically included in an ADU plan set
- Site plan showing the ADU's placement relative to the primary home, setbacks, and lot lines
- Foundation plan
- Floor plan showing all rooms, including kitchen/bath if applicable
- Exterior elevations
- Cross section and roof plan
- Electrical plan
This is effectively the same Full Architectural Plan Set structure used for a new home—just scaled to a smaller footprint. See What's Included in a Full Plan Set? for detail on each sheet.