Junior ADU (JADU)

Carving a second home out of an existing house, rather than building a new structure, is the whole idea behind a junior accessory dwelling unit, or JADU. It is built within the walls of the main home, often from a converted bedroom or garage area, and is typically capped around 500 square feet. A JADU has its own exterior entrance and at least a small kitchen, and it may share a bathroom with the primary house.

The point of a JADU is to add a self-contained living space without building a whole new structure. Because it reuses space already inside the house, it usually costs less than a detached unit and avoids new foundation, roofing, and exterior walls. Owners use JADUs for aging parents, adult children, a home office with a kitchenette, or rental income.

The key difference is scale and construction. A full accessory dwelling unit (ADU) is a complete, independent home, often detached, with its own kitchen and bathroom. A casita is the common Arizona term for a guest house or detached ADU. A JADU is smaller, sits inside the existing home, and may share plumbing, so it is the lightest-weight option of the three.

Arizona has moved to make these units easier to add. A.R.S. 9-461.16 directs many municipalities to allow accessory dwelling units on single-family lots and limits how restrictive local rules can be, which has pushed cities across the Phoenix metro to update their codes. Local rules still govern size limits, setbacks, parking, and owner-occupancy, and they vary by city. For example, a homeowner in Tempe or Phoenix might convert part of a large house into a JADU for a parent, while keeping the main home intact. Before designing one, we confirm the specific city's current ADU and JADU rules, since they are changing quickly.