The popularity of Accessory Dwelling Units (ADU) is increasing across California, especially in cities such as San Diego where there is a high demand for housing.
From the design point of view, an auxiliary housing unit (ADU) is a secondary living space that is built on the same plot as an existing house. It is sometimes called a granny flat, casetta or in-law suite.
But the big question is: Is it cheaper to add anything else to your home, or to make Adu? And what is its real cost in California? Let's understand this.
Adu is changing thinking about the value, income and flexibility of housing of the property of the owners of the house. But are they worth investing? Let us consider it step by step.
In this 2025 guide, we will answer the most common ADU questions: what adu means, why some people oppose them, the difference between home and Adu, Permit Rules in California and how to start the Adu process.