ADU Construction in Boise, Idaho

Choosing the right kind of ADU

The right ADU depends on three things: your lot, your budget and how the unit will be used. A detached cottage gives both households the most privacy and usually the strongest rental appeal, but it needs its own foundation and longer utility runs. A conversion reuses a structure you already have, which typically costs less and moves faster, but it's limited by the shape and condition of that space.

Boise has made both easier. The city no longer requires owner occupancy or an added parking space for an ADU, and in 2026 it began offering free pre-approved plans for detached units. Idaho's 2026 ADU law extends similar rules to Meridian, Eagle, Garden City and other cities over 10,000 people by February 2027.

Every project starts with a lot check: zoning, setbacks, easements, floodplain and utilities for your address. From there you get a written estimate covering design, permits and construction, so you can compare options before committing. See typical budgets in the ADU cost guide, or check your city on the service areas page.