Regulations for Accessory Dwelling Units (ADU)
General Definition
- ADUs are units with living space that are an accessory use to the main building.
- ADUs CAN be attached to the main house or in a detached building. Basement ADUs are permitted if interior access to the upstairs is maintained.
- ADUs CANNOT be recreational vehicles or travel trailers.
General Guidelines
- Code Reference: Ammon City Code Title 10 Chapter 7 Section 4.
- Permitting: Must be permitted with the Ammon Building Department.
- Limit: Only one (1) ADU is allowed per lot; a main house must already exist on the property.
- Ownership: Must be under the same ownership as the main house; cannot be subdivided.
- Access: Must use the same driveway access as the main house. Attached units must have a separate exterior access.
- Allowed Zones: RE, RP, RP-A, and R-1 Zones.
Size and Coverage
- Max Size: 75% of the living space above grade of the main house or 1,000 square feet, whichever is more restrictive.
- Backyard Coverage: Only 30% of the backyard may contain covered structures (includes shops, sheds, patio covers, etc.).
Location and Setbacks
- ≥ 12' Behind House: Minimum 3-foot setback from property line (subject to snow/water runoff requirements).
- < 12' Behind House: Must maintain the standard setbacks of the specific zone.
- Separation: Minimum 3 feet from any other structure (otherwise, proper firewalls are required).
- Drainage: All snow/water must remain on the property; it cannot fall on neighboring property or sidewalks.
Address and Utilities
ADUs will NOT be given a separate address. All utilities MUST connect through the main house. No additional service lines can be added for the ADU.
Additional Questions?
Ammon Planning and Zoning Department: (208) 612-4000 (Option 6)