1 county-level rule, plus city-specific rules for 1 city in Boone County, Missouri.
Verified from official government sources
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.
Boone 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...
1 cities in Boone County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
See every category we cover for Boone County — parking, noise, fences, fires, animals, pools, and more.
Boone County Ordinance Hub →