ADU Regulations in Idaho (ID)
Idaho is rated Moderate for ADU construction with an ADU-friendliness score of 30/100 (Restrictive). Idaho does not have a statewide ADU law — regulations are set entirely by local jurisdictions. Owner must reside on the property. Additional parking may be required. Idaho has no statewide ADU law, but Boise and several growing cities have adopted local ADU ordinances in response to housing shortages. The state legislature has considered but not passed ADU reform. Local regulations vary significantly.
Full ADU Regulations Summary for Idaho
| ADUs Allowed | Yes |
| Statewide ADU Law | No |
| Maximum ADU Size | Set locally |
| Owner Occupancy Required | Yes |
| Parking Required | Yes |
| Minimum Setback | Set locally |
| Permitting Timeline | Varies by jurisdiction |
| Impact Fees | Varies by jurisdiction |
| Long-Term Rental Allowed | Yes |
| Short-Term Rental (Airbnb) Allowed | Yes |
| Ease of Building | Moderate |
ADU Regulations by City in Idaho
ADU rules can vary by city even within the same state. Without a statewide ADU law, Idaho cities set their own rules, and policies can differ significantly. Below are ADU details for 3 cities in Idaho.
Boise
ADUs allowed by right on single-family lots since 2020. Maximum 900 sq ft. Owner occupancy required. One parking space required.
Meridian
ADUs permitted with conditional use approval in residential zones. Stricter requirements than Boise.
Coeur d'Alene
ADUs allowed in certain residential zones. Regulations updated in 2023 to address housing demand.
How Idaho Compares to Other States
Below is a comparison of Idaho with five states that have similar ADU-friendliness scores. This comparison helps illustrate where Idaho stands nationally.
| State | Score | Statewide Law | Parking Req? | Owner Occ? | Ease |
|---|---|---|---|---|---|
| Idaho (ID) | 30 | No | Yes | Yes | Moderate |
| Alabama (AL) | 30 | No | Yes | Yes | Difficult |
| Delaware (DE) | 30 | No | Yes | Yes | Moderate |
| Georgia (GA) | 30 | No | Yes | Yes | Moderate |
| Illinois (IL) | 30 | No | Yes | Yes | Moderate |
| Indiana (IN) | 30 | No | Yes | Yes | Difficult |
Frequently Asked Questions About ADUs in Idaho
Can I build an ADU in Idaho?
Yes, ADUs are allowed in Idaho. However, Idaho does not have a statewide ADU law, so the specific rules depend on your city or county's zoning code. Some cities are more permissive than others. The ease of building is rated "Moderate" with a friendliness score of 30/100.
Do I need to live on the property to have an ADU in Idaho?
Yes, Idaho generally requires owner occupancy — the property owner must live either in the main house or the ADU. This means you cannot rent out both units simultaneously. Note: individual cities may have their own owner-occupancy rules, so check your local zoning.
How big can an ADU be in Idaho?
Idaho does not set a statewide maximum ADU size — this is determined by your local jurisdiction. Common local limits range from 600 to 1,200 square feet. Check your city's zoning code for the specific maximum.
How long does it take to get an ADU permit in Idaho?
The permitting timeline in Idaho is: Varies by jurisdiction. Without a statewide mandate, permitting timelines depend entirely on your local jurisdiction's review process.
Who decides ADU rules in Idaho?
Your city or county — Idaho has no statewide ADU statute, so zoning boards set the rules jurisdiction by jurisdiction. We track 3 Idaho cities above (including Boise); if yours isn't listed, the planning or zoning office is the authoritative source.
Check ADU Rules for Your City
Use our ADU regulations lookup tool to find the specific rules for your city in Idaho, or browse all 50 states to compare ADU regulations across the country.