What Is the Cost of Building an ADU in California?

The cost of building an ADU in California varies based on factors such as size, design, site conditions, utility work, and local fees. A statewide homeowner survey found that the median ADU construction cost is $150,000, or approximately $250 per square foot, providing a useful benchmark for homeowners planning an ADU. The California Department of Housing and Community Development notes that ADUs are “an affordable type of home to construct in California” (California Department of Housing and Community Development). For many homeowners, ADUs offer a practical way to add living space, generate rental income, and increase property value. “The median statewide construction cost of an ADU is $150,000, or $250 per square foot.” (Terner Center for Housing Innovation)