Accessory Structures in Boise, ID (2026)
5 verified accessory structures rules for Boise, Idaho, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Boise allows up to two accessory dwelling units per single-family lot, capped at 900 square feet or 70% of the primary home's floor area, with no more than two bedrooms and two stories in height.
Boise Accessory Dwelling Unit (ADU) Rules
Some RestrictionsBoise City Code § 11-03-03.2.B
ADUs are permitted only as an accessory use to a single-family dwelling (attached or detached). A lot or parcel may contain up to two accessory residential units in any combination of ADUs or Tiny Homes on Wheels (THOW). Maximum density standards shall not apply to ADUs. The ADU shall not be larger than 900 square feet or 70 percent of the total floor area of the primary building, whichever is ...
ADU Owner Occupancy
Inside the Harris Ranch Specific Plan area, Boise requires the principal home or its accessory dwelling to stay owner-occupied on an ongoing basis. The Planning Director cannot approve the accessory dwelling unless that commitment is recorded as a deed restriction with the Ada County Recorder before occupancy begins.
Boise Harris Ranch ADU Owner-Occupancy Rule
Significant RestrictionsBoise City Code § 11-07-01.8.C.(12)(g)
That on-going owner-occupancy of either the principal or the accessory dwelling is required and shall be enforced through recordation of a deed restriction to that effect with the Ada County Recorder. A temporary waiver of this requirement may be granted by the Planning Director in the case of a documented need for the owner-occupant to leave the premises for up to 1 year due to employment, ill...
Shed & Carport Rules
Detached carports in Boise can't sit in front of the house or encroach into front and street-side setbacks without a conditional use permit, though one-story carports under 200 square feet skip a building permit entirely.
Boise Carport Setback and Permit Rules
Some RestrictionsBoise City Code § 11-03-03.1.B(3)(c)
No detached accessory building or structure shall occupy any area in front of the primary building, unless approved by the Planning and Zoning Commission as a conditional use permit. However, on lots that have topographical or other physical constraints, the Planning Director may approve a detached accessory building or structure in front of the primary building. ii. Regardless...
Garage Conversions
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.
Boise Garage Conversion to ADU Space
Some RestrictionsBoise City Code § 11-03-03.2.B(6)(f)
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.
Tiny Homes
Boise allows a tiny home on wheels as an accessory unit to a single-family home, capped at 400 square feet and subject to permitted utility hookups.
Boise Tiny Homes on Wheels Rules
Some RestrictionsBoise City Code § 11-03-03.2.P
P. Tiny Homes on Wheels (THOW): (1) Maximum density standards shall not apply to THOW. (2) THOW are permitted only as an accessory use to a single-family dwelling (attached or detached). (3) A lot or parcel may contain up to two accessory residential units in any combination of ADUs or tiny homes on wheels (THOW). (4) The THOW structure shall be no larger than 400 square feet in size. (5) A THO...
Looking for Ada County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Boise city rules.
Accessory Structures in Ada County →