A rough estimate is $225-$300/SF but like others have said, it varies based on site conditions, design, and finishes.

My company specializes in ADU design and planning. We can provide preliminary estimates based on your project scope and help you with bidding the project out to local contractors to get the best value.

You can check us out at Buildoly - we are a New England based ADU platform that helps homeowners design, permit, and build custom ADUs in one streamlined process. If you send me a message, I'd be happy to provide a free feasibility report & cost estimate on your intended property. You can also sign up for a consultation and we'll guide you through the entire process and provide insights specific to your ADU build.