ADU rules in Ada County, ID — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Unincorporated Ada County allows one secondary (accessory) dwelling per lot of at least 6,000 square feet. It must be 350 to 1,200 square feet, or 60% of the principal home's above-ground living space, whichever is less, and capped at three bedrooms.
Ada County Code Title 8 (Zoning), Section 8-4-23 governs secondary attached or detached dwellings on unincorporated land. A principal dwelling with a certificate of occupancy must already exist. Only one additional dwelling is allowed per property, on a lot of at least 6,000 square feet, and the owner must occupy either the principal or the secondary dwelling. The unit must be 350 to 1,200 square feet (or 60% of the principal home's above-ground living space, whichever is less), have no more than three bedrooms, separate kitchen and bath, its own entrance and address, and sit on a foundation. A recorded deed restriction is required. Inside Boise, Meridian, Eagle, Kuna, or Star, the city's ADU rules apply.
Building or renting a secondary dwelling without meeting Section 8-4-23 (size, occupancy, deed restriction) is a zoning violation enforced by Ada County Development Services.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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Ada County has no ordinance banning backyard composting. Home compost piles are allowed, but they must not become a nuisance, attract rodents or vermin, or c...
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Ada County has no ordinance banning or specifically regulating residential artificial turf. Installation on private property is generally allowed; check drai...
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Ada County does not require any particular landscape plants and does not ban native or xeric plantings. As long as growth is not an overgrown-weed nuisance o...
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Ada County has no ordinance banning rooftop rainwater collection. Under Idaho water law, capturing rain and snowmelt from your own roof for use on your prope...
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Ada County itself sets no residential watering schedule. In the Treasure Valley, outdoor irrigation typically comes from irrigation districts (Nampa-Meridian...
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Ada County declares overgrown weeds and grasses a public nuisance when they create a fire, safety or health hazard, or interfere with neighbors' use of their...
See how Ada County's adu rules rules stack up against other locations.
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