ORDINANCE GUIDEEffective Feb 2026
Boise ADU Guide
A summary of Boise ADU rules under ZOA25-000013 (2026), including maximum size, setbacks, owner-occupancy, parking, and the eight free pre-approved plans.
This guide summarizes Boise accessory dwelling unit rules based on City of Boise Zoning Code amendment ZOA25-000013. Effective date: 2026-02-15. This is not legal advice. Standards change. Verify all information at https://www.cityofboise.org/departments/planning-and-development-services/planning/boise-zoning-code/pre-approved-adu-plans/ before making any development or acquisition decision.
Renew analysis
Where this pathway usually breaks. And where it actually works.
Investors can now develop two ADUs on a single lot, doubling rental income potential compared to the previous one-ADU limit. This applies to detached, attached, and junior ADU configurations.
The 70% rule allows larger ADUs on properties with larger primary dwellings, creating flexibility for higher-end rental units. Junior ADUs offer a lower-cost conversion path for existing interior space.
Alley-facing lots gain buildable area, making ADU development viable on smaller or constrained parcels. This is particularly valuable in established neighborhoods like The Bench and North End.
Transit-proximate properties eliminate parking construction costs, improving ADU project economics. Verify transit corridor maps before acquisition.
Non-owner-occupied investment properties can now add ADUs without triggering occupancy restrictions, expanding the investor pool and rental inventory potential.
Pre-approved plans eliminate architectural design costs and accelerate permitting timelines, reducing soft costs and time-to-market for ADU projects.