Typical accessory dwelling costs in California

How much does an accessory dwelling (ADU) cost to design and build in California?

An accessory dwelling unit is a deeply personal thing. Every property, home, and homeowner is different. Your needs, tastes, and site will be different from those of your neighbor. So naturally, design, permitting, and construction costs will vary from project to project.

In the Bay Area in 2019, you can expect a 650-square-foot ADU to cost around $350,000. A 350-square-foot ADU will likely cost around $225,000. Of course, your costs may be more or less, depending on what you want for your accessory dwelling unit.

Let’s get a little more specific. Although your experience will be unique, you can get an idea of what it will cost by looking at similar projects. Here’s a look at some real costs for accessory dwellings in the Bay Area.

• A 650-square-foot accessory dwelling in El Cerrito cost $290,322.75 to design and build. It has one bedroom, one bathroom, a kitchen/living area, and a loft.

• A one-bedroom, one-bathroom ADU in Santa Cruz cost $315,194.77 to design and build. It’s attached to a garage, which is shared with the main home.

• A cottage in Berkeley cost $280,276.00 to design and build. It has two bedrooms, a bathroom, a kitchen, and a living area. (This one is a great story of a real family effort.)

• A 374-square-foot, versatile space in Concord, CA, can be used for anything the homeowner wants. It includes a living area, a bathroom, a kitchen, and storage cabinets. The total cost was $228,668.24

If you’re adding an accessory dwelling to your home in the San Francisco Bay Area, expect to spend between $225,000 and $550,000 for design, permitting, and construction.