Cost to build accessory dwelling unit — Boise City, ID

Last updated: September 24, 2026

What affects the price

Building an ADU involves several moving parts that shape your total investment. The final figure depends heavily on whether you choose a prefab unit or a custom build from the ground up. Site conditions are another major factor; if your property requires extensive grading, utility trenching, or foundation work, costs will climb. You also have to consider your choice of finishes, like high-end appliances or custom cabinetry. Navigating local permit fees and impact assessments also adds to the total.

About this service

When estimating the cost to build, consider the difference between a prefab unit and custom construction, as well as site preparation requirements like clearing trees or grading land. Labor and material prices also play a significant role. We provide an exact pricing confirmed free on the call.

Frequently asked in Boise City

Also serving nearby: Meridian · Nampa · Bend · Spokane Valley · Spokane

All cities in Idaho →

More on this: HUD ADU resources — ADU policy and financing research.

Service area details

Serving all of Boise City — population 235,421; about 2,784 residents per square mile across 84.6 sq mi.

Neighborhoods served in Boise City: Meridian, Nampa, Bend, Downtown Boise, The North End, East Boise — and every surrounding area.