Boise, ID Accessory Structures: Garage Conversions (2026)
Garage conversion rules in Boise, ID, sometimes called garage-to-ADU or accessory living unit conversions, govern permits, ceiling height, egress, and parking replacement.
Key Facts
- Size cap
- 900 sq ft or 70% of home, smaller
- Parking
- Must replace parking lost on same lot
- Bedrooms
- Max two bedrooms per ADU
- Height
- Max two stories
- Review
- Zoning review plus building permit required
Summary
Boise allows turning a garage into living space as an accessory dwelling unit, but only if replacement off-street parking is sited elsewhere on the lot and the unit stays under 900 square feet.
The ADU shall not be larger than 900 square feet or 70 percent of the total floor area of the primary building, whichever is smaller, and shall not have more than two bedrooms... The ADU shall be created through one of the following: ... (f) Conversion of an existing detached accessory structure or attached garage that does not reduce off-street parking below the minimum required for that lot.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-31: Code current through: Ord. 20-26, passed 6-9-2026).
Full Breakdown
Boise City Code § 11-03-03.2.B lets homeowners convert an attached or detached garage into an accessory dwelling unit, but only if the conversion "does not reduce off-street parking below the minimum required for that lot", meaning replacement parking must be sited legally elsewhere on the property first. The finished unit is capped at 900 square feet or 70 percent of the primary dwelling's floor area, whichever is smaller, with no more than two bedrooms and no more than two stories. It must also meet the dimensional standards of the underlying zoning district and the City's adopted Building Code, so review and a building permit are required before work begins.
Violations & Fines
Converting a garage without meeting ADU parking, size, and design standards or without a permit can trigger a stop-work order and code enforcement action from Boise's Planning and Development Services.
Frequently Asked Questions
Can I convert my Boise garage into a bedroom or rental unit?
Do I need a permit to convert a garage in Boise?
Sources & Official References
Other rules in Boise
Compare Boise to another location·View the Idaho accessory structures overview
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