How much does it cost to build an ADU?
May 2, 2026 · contractor
Thinking about adding an accessory dwelling unit for family. What's a realistic cost range and what drives it up?
1 answer
Best answer
ADUs typically run $100,000–$300,000+ depending on size, whether it's a conversion (garage) or new build, and local permit/utility costs. Garage or basement conversions are usually the cheapest path. Design, foundation, and utility hookups drive most of the price. Start with a local pro who knows your city's ADU rules — they vary a lot.