ADU rules in Bowling Green

Bowling Green zoning is the Warren County joint Zoning Ordinance, which allows one accessory apartment per lot by right in the R-E and RS-1A through RS-1D single-family districts (the RR district is county only), as well as in AG and several commercial districts. A detached accessory apartment must sit in a side or rear yard and meet all building setbacks, with no variance or waiver available for that location rule. The catch is occupancy: the unit is limited to relatives of the household, a caregiver, or the owner (see rental restrictions).

The same accessory apartment may be attached to or inside the house (the definition names basement apartments and extensions of the primary structure). Any entrance to an attached unit must be on the side or rear facade, and the unit must not alter the single-family character of the house or the neighborhood's development pattern.

The accessory apartment's floor area may not exceed 50 percent of the floor area of the principal structure, and it may have no more than two bedrooms. A 2019 staff interpretation counts only conditioned, enclosed space on both sides of the comparison (garages, carports and covered patios are excluded). Accessory buildings in single-family districts may not rise above the tallest point of the principal structure's roof, and in Bowling Green all accessory buildings together may not exceed the principal building's footprint. The square-footage waiver available for other accessory structures expressly excludes accessory apartments.

Accessory apartments may only be located on lots where the primary residence is occupied by the property owner. The owner may instead live in the accessory apartment, but only if the main house is then occupied by the owner's relatives. The requirement is an ongoing use standard, not just an application condition.

At least one off-street parking space is required for the accessory apartment, in addition to the spaces required for the primary residence (two for a single-family home in the RS districts).

Accessory apartments are a permitted residential unit type ('P') in the single-family districts, so the normal route is a building permit issued by the Building Inspector after zoning review, with no Board of Adjustments hearing. Lots in local historic districts also need Historic Preservation Board review of new construction, and the Nutwood/Magnolia overlay adds architectural standards for accessory apartments.

An accessory apartment may only be occupied by people related by blood, marriage, adoption, guardianship or custodial relationship to those living in the main house, plus at most one caregiver serving someone on the property, so renting it to an unrelated tenant is not allowed. Short-term rental (stays under 30 days) is not a listed use in the RS-1 districts at all; it needs a Board of Adjustments conditional use permit in AG, R-E and the RM districts and a Planning Commission short-term rental license wherever it is allowed.