Accessory Structures in Boone County, MO (2026)
3 county-level rules, plus city-specific rules for 1 city in Boone County, Missouri.
Verified from official government sources
ADU Rules
Missouri has no statewide ADU mandate; ADU regulation is delegated to counties under Mo. Rev. Stat. Ch. 64. The Boone County Zoning Ordinance (administered by Resource Management at 801 E. Walnut St., Columbia) treats accessory dwellings as accessory structures or as conditional uses depending on district. The County is actively considering expanded ADU allowances under its 2026 Affordable Housing public hearing process; until adopted, second dwelling units typically require a conditional use permit and must meet the underlying district's lot size and setback rules.
Accessory Dwelling Units in Unincorporated Boone County
Some RestrictionsBoone County Zoning Regulations § 7.1.3 (Accessory dwelling - A-1, A-2, A-R, R-S Districts)
7.1.3 A single accessory dwelling is allowed on legally created individual parcels in the A-1, A-2, A-R, and R-S Districts subject to the following: 7.1.3.1 There shall be a minimum separation of 10 feet between the primary and accessory dwelling unless they are attached by a common wall. 7.1.3.2 The accessory dwelling shall not exceed 75% of the total square feet of the primary dwelling or 1,5...
Shed & Carport Rules
Boone County zoning bars building a shed or other accessory structure before the main house is under construction, and bans using it as a residence unless the main dwelling is also occupied.
Boone County Shed & Accessory Building Rules
Some RestrictionsBoone County Zoning Ordinance § 7.1.5.1
No accessory building shall be constructed upon a lot until the construction of the main building has actually commenced, and no accessory building shall be used unless the main building on the lot is also being used with the following exceptions: � The use of a temporary construction shed or road wagon for the storage of tools, material, and...
Garage Conversions
Boone County zoning bans converting a garage or other accessory building into living space, with the only exception being an approved accessory dwelling unit.
Boone County Garage Conversion Restrictions
Significant RestrictionsBoone County Zoning Ordinance § 7.1.5.4
Accessory buildings may not be used for dwelling purposes except as provided in 7.1.3 and 7.4.1 above.
Accessory Structures by City in Boone County
1 cities in Boone County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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