No, you cannot legally build an Accessory Dwelling Unit (ADU) without a permit in California. The process of building an ADU requires obtaining the proper city and county permits before construction begins. These permits ensure that the ADU complies with local zoning, building codes, and safety regulations.
The specifics of these permits can vary widely by city and county. For example, in San Francisco, ADU permits can cost anywhere from six to nine percent of your construction costs. The costs are typically based on the complexity of the ADU project, the size of the unit, and the value of the construction1.
Building an ADU without the necessary permits can lead to serious consequences, including fines, legal actions, and the potential requirement to demolish the un-permitted construction. Therefore, it is crucial to follow all local regulations and obtain all necessary permits before starting the construction of an ADU.
