10 States Where ADU Costs Dropped 25% in 2025
In 2025, ten U.S. states report approximately 25% reductions in ADU construction costs due to abundant materials, efficient permitting processes, and heightened builder competition. Residents in California, Oregon, Washington, and seven others now find it feasible to construct affordable detached cottages or interior conversions. These developments transform expensive expansions into practical investments that enhance property value and generate rental revenue.







