Idaho adu city regulations
Boise
Accessory dwelling units are permitted on lots with a primary single-family home, with a maximum size of up to 1,000 square feet or 40% of the primary home's size (whichever is smaller), allowing up to two bedrooms, reduced parking requirements, and owner occupancy of the property required, following 2019 and 2023 zoning updates that eased prior restrictions from 600 sq ft and one bedroom.
Meridian
Accessory dwelling units are allowed in residential zones with a maximum size of 900 square feet and limited to one bedroom, requiring attachment to the primary dwelling on lots under a certain size and owner occupancy of the main home.
Eagle
Accessory dwelling units are permitted as accessory uses in residential zones, subject to size limits not exceeding 900 square feet, one bedroom maximum, and compliance with setbacks and design standards matching the primary structure; contact Eagle Planning for precise ordinance details as specific limits are not detailed in statewide summaries.
star
Accessory dwelling units are allowed in single-family residential zones up to 800 square feet with no more than one bedroom, must be attached or detached with rear-yard placement, and require owner occupancy of the primary residence; short-term rentals are prohibited.
Kuna
Accessory dwelling units may be permitted through conditional use approval in agricultural and rural residential zones, with size limits up to 1,000 square feet or 50% of the primary home, requiring septic approval and no separate utilities; variances may be needed for detached units.
Garden city
Accessory dwelling units are restricted to attached configurations (e.g., basement or garage conversions) up to 750 square feet with one bedroom maximum, must maintain neighborhood compatibility, and require connection to existing utilities without separate metering.
Nampa
Accessory dwelling units are permitted in residential zones with a maximum size of 500 square feet and limited to one bedroom, requiring rear or side yard placement for detached units, owner occupancy of the primary home, and approval from the health district for sewage connections.
caldwell
Accessory dwelling units are allowed on single-family lots up to 900 square feet with one bedroom, must be subordinate in design to the main house, include one off-street parking space, and comply with general zoning setbacks; short-term rentals under 30 days are prohibited.
middleton
Accessory dwelling units require conditional use permits in residential districts, limited to 800 square feet or 40% of the primary dwelling (whichever is smaller) with one bedroom, owner occupancy required, and must meet fire separation and utility tie-in standards.
emmett
Accessory dwelling units are permitted in rural residential zones up to 1,000 square feet as secondary dwellings, subject to minimum 1-acre lot size, health department septic approval, and no more than one per property with the primary home owner-occupied.
Parma
Accessory dwelling units may be approved via administrative permit in agricultural and residential areas, with size caps at 750 square feet and one bedroom, requiring compliance with flood zone rules if applicable and connection to shared utilities.
wilder
Accessory dwelling units are allowed as accessory uses on larger lots (minimum 5 acres in ag zones), up to 900 square feet with one bedroom, must include sewage disposal approval, and are limited to one per parcel with design compatibility to the main structure.
melba
Accessory dwelling units require zoning compliance review and are limited to 600 square feet maximum in rural areas, with owner occupancy and no short-term rental use allowed; septic permits mandatory.
mountain home
No specific ADU regulations or size limits found in public sources; ADUs may be permitted as accessory uses in residential zones subject to general zoning setbacks, building codes, and health department approvals—contact Mountain Home Planning and Zoning for details.
idaho city
No specific ADU regulations or size limits found in public sources; contact Boise County Planning for local guidelines, as unincorporated areas like Idaho City follow county rules.
new plymouth
No specific ADU regulations or size limits found in public sources; ADUs may be allowed via conditional use permits in residential or agricultural zones subject to county setbacks and health approvals—contact New Plymouth City Hall or Payette County Planning for details.
Idaho adu county regulations
Ada
Accessory dwelling units (ADUs) in unincorporated areas are limited to a maximum of 1,200 square feet or 20% of the lot area, whichever is smaller, with no more than one bedroom.
Adams
No specific ADU regulations or size limits found in public sources; contact Adams County Planning and Zoning for local guidelines.
bannock
ADUs are permitted with a minimum size of 300 square feet and a maximum of 900 square feet, though larger sizes may be allowed with a variance; one ADU per lot in residential zones.
Bear lake
No specific ADU regulations or size limits found in public sources; contact Bear Lake County Planning for details.
Benewah
No specific ADU regulations or size limits found in public sources; contact Benewah County Planning for details.
Bingham
No specific ADU size limits identified; ADUs may be permitted as accessory uses in residential zones subject to general zoning setbacks and lot coverage rules—consult Bingham County Planning and Development.
Blaine
No specific ADU regulations or size limits found in public sources; contact Blaine County Planning and Zoning.
Boise
No specific ADU regulations or size limits found in public sources; contact Boise County Planning.
Bonner
ADUs are limited to a maximum of 900 square feet with no more than two bedrooms; one ADU per lot, must be attached on lots under 20,000 square feet.
Bonneville
No county-wide ADU size limits specified; in Idaho Falls (within county), maximum 750 square feet with one bedroom—check with local municipalities for variations.
Boundary
No specific ADU regulations or size limits found in public sources; contact Boundary County Planning.
Butte
No specific ADU regulations or size limits found in public sources; contact Butte County Planning.
Camas
No specific ADU regulations or size limits found in public sources; contact Camas County Planning.
canyon
No county-wide ADU size limits; follows local city rules (e.g., Nampa: max 500 sq ft, one bedroom; Caldwell: max 900 sq ft, one bedroom)—zoned residential properties only.
caribou
No specific ADU regulations or size limits found in public sources; contact Caribou County Planning.
cassia
ADUs are restricted to no greater than 1,000 square feet; requires health department permit for sewage and owner notification to buyers.
clark
No specific ADU regulations or size limits found in public sources; contact Clark County Planning.
clearwater
No specific ADU regulations or size limits found in public sources; contact Clearwater County Planning.
custer
No specific ADU regulations or size limits found in public sources; contact Custer County Planning.
elmore
ADUs are limited to a maximum of 900 square feet; permitted as accessory to single-family dwellings with administrative approval.
Franklin
No specific ADU regulations or size limits found in public sources; contact Franklin County Planning.
fremont
No specific ADU regulations or size limits found in public sources; contact Fremont County Planning.
GEM
ADUs (secondary dwellings) are permitted up to 1,800 square feet in gross floor area in zones allowing residential uses; requires owner occupancy and minimum 5-acre lot in agricultural zones.
Gooding
No specific ADU regulations or size limits found in public sources; contact Gooding County Planning.
idaho
No specific ADU regulations or size limits found in public sources; contact Idaho County Planning.
jefferson
No specific ADU regulations or size limits found in public sources; contact Jefferson County Planning.
jerome
No specific ADU regulations or size limits found in public sources; contact Jerome County Planning.
kootenai
In unincorporated areas, accessory living units (ALUs) shall not exceed 1,000 square feet or 50% of the primary structure's habitable space, whichever is greater.
latah
No specific ADU size limits identified; ADUs permitted as conditional uses in certain zones—contact Latah County Planning & Building for details.
lemhi
No specific ADU regulations or size limits found in public sources; contact Lemhi County Planning.
lewis
No specific ADU regulations or size limits found in public sources; contact Lewis County Planning.
lincoln
ADUs require a health department permit for sewage disposal; no specific size limit detailed in available sources—consult Lincoln County for full ordinance details.
madison
No specific county-wide ADU size limits; proposed rules include minimum 2-acre lot and attached to primary dwelling—check with Madison County Planning & Zoning or cities like Rexburg.
minidoka
No specific ADU regulations or size limits found in public sources; contact Minidoka County Planning.
nez perce
No specific ADU regulations or size limits found in public sources; contact Nez Perce County Planning (note: Lewiston city may have separate rules).
oneida
No specific ADU regulations or size limits found in public sources; contact Oneida County Planning.
owyhee
No specific ADU regulations or size limits found in public sources; contact Owyhee County Planning.
payette
No specific ADU regulations or size limits found in public sources; contact Payette County Planning.
Power
No specific ADU regulations or size limits found in public sources; contact Power County Planning.
Shoshone
No specific ADU regulations or size limits found in public sources; contact Shoshone County Planning.
teton
No specific ADU regulations or size limits found in public sources; contact Teton County Planning (note: Driggs and Jackson may have rules).
twin falls
No specific ADU size limits; accessory structures under 1,000 square feet may not require permits, but ADUs must comply with residential zoning—consult Twin Falls County Planning.
valley
ADUs may not exceed the lesser of 1,000 square feet or 50% of the primary structure's square footage (excluding garages); owner occupancy required.
washington
No specific ADU regulations or size limits found in public sources; contact Washington County Planning.
