ADU rules in Oldham County

A detached accessory dwelling unit (a separate building, including a garage apartment joined to the house only by a breezeway) needs a conditional use permit from the Board of Adjustments after a public hearing. It is available in the AG-1, CO-1, R-1, R-1A, R-2 and R-2A districts (the AG-2 use table also lists it as a conditional use), not in R-3, R-4, R-4A, T or the commercial districts. The unit must meet the setbacks for a primary structure, stand at least 5 feet from the house, sit behind it, and counts as a whole dwelling unit toward the district's density limit. The county board granted such permits on 6-18-2026 and heard two more on 10-15-2026.

Interior units (inside the footprint of a new or existing house) and attached units (an addition to the house's floor area) are allowed by right with a building permit when the general conditions are met. Interior units are listed for AG-1, CO-1, R-1, R-1A, R-2 and R-2A; the attached-unit text lists AG-1, CO-1, R-1, R-2 and R-2A, although the R-1A and AG-2 use tables list both forms as permitted. An attached unit needs a permanent interior connection through a common wall (a breezeway does not count), and neither form counts toward density.

Detached units may not exceed 25 percent of the primary structure's square footage, and attached units may not exceed 30 percent of its finished square footage; the ordinance sets no fixed square-foot cap and no separate limit for interior units. Both detached and attached units are limited to the height of the house. The Board of Adjustments may grant variances from these standards: on 6-18-2026 it allowed an 864 sq ft unit where the 25 percent rule on a 2,576 sq ft house yielded 644 sq ft (a 220 sq ft variance).

The property owner must live in either the main house or the accessory unit, and at building permit application the owner signs an accessory dwelling unit affidavit. The requirement is written as a standing condition, not only an application-time test. Kentucky has no state ADU law that would preempt it.

The ADU section requires off-street parking for the accessory unit but does not say how many spaces. The parking tables require at least 2 spaces per dwelling unit for single-family detached homes and duplexes, and uses not listed are set by the Administrator from the closest comparable use, so expect staff to ask for at least one added space; the count applied in practice was not confirmed.

Interior and attached units are by right with a building permit (staff review plus the owner-occupancy affidavit). Detached units require a conditional use permit from the Board of Adjustments after a public hearing with mailed and newspaper notice, and no certificate of land use issues until the board's minutes are approved at its next meeting. Applications in the unincorporated county and Crestwood go to the Oldham County Board of Adjustments; La Grange keeps its own Board of Adjustments for land inside its limits.

The ADU section does not bar long-term rental, though the owner must live on the property and the unit may not have separate utility services unless codes or the provider require them. Short-term rental of any dwelling unit, ADUs included, falls under §250-050: an annual Short Term Rental Property permit from Planning and Development Services is required, and in every residential and agricultural district only an owner-occupied host (primary residence on the same or an adjacent lot) may operate, by conditional use permit; non-owner-occupied short-term rentals are not permitted there. The Board of Adjustments has also attached a no-short-term-rental condition to a detached ADU permit (8003 Shadow Creek Road, 6-18-2026).