5 county-level rules, plus city-specific rules for 1 city in Jefferson County, Kentucky.
Verified from official government sources
Jefferson County (Louisville Metro) allows ADUs on single-family lots under LDC § 4.3.27 (2021 amendment). ADUs are limited to 800 sq ft or 30% of the main home. Owner occupancy of the main home or ADU is required. ADUs under this provision cannot be used as short-term rentals. Most approvals are administrative.
In Jefferson County (Louisville Metro), one-story detached accessory structures under 200 sq ft need no building permit. Structures 200 sq ft or larger require a permit. The combined footprint of all accessory structures cannot exceed the main house footprint. Maximum height is 24 feet or the main house height (whichever is lower).
Garage conversions to living space in Jefferson County (Louisville Metro) require a building permit. Converting to an accessory apartment may require a Conditional Use Permit or follow the ADU process under LDC § 4.3.27. All work must meet Kentucky Residential Code standards.
Louisville Metro requires a building permit for carports exceeding 200 sq ft under 2018 Kentucky Residential Code. LMCO Land Development Code sets side setback of 3-5 feet and counts carports toward lot coverage.
Louisville Metro regulates tiny homes via 2018 Kentucky Residential Code Appendix Q for units under 400 sq ft. THOWs typically classified as RVs and restricted to RV parks. ADU ordinance (2020) allows tiny accessory dwellings.
1 cities in Jefferson County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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