ADU rules in Frankfort

Frankfort allows accessory dwelling units only as a conditional use in the two historic overlay-style districts: the Special Historic (SH) district (§4.403 L) and the Special Capitol (SC) district (Conditional Uses list under §4.412, item L). Ord. 14, 2025 Series (adopted 8-25-2025) added the ADU definition, which covers new stand-alone accessory structures and converted accessory structures, and these two use listings; staff called it a stopgap ahead of the full development code rewrite. The ordinary single-family districts (RE, RA, RB, RC) and every other district in the §4.05 land use table list no ADU use, so a backyard unit there is not allowed.

The same definition counts converted portions of an existing home (internal ADUs) and additions (attached ADUs) as accessory dwellings, and they get the same treatment: a conditional use in the SH and SC districts only. Outside those districts the only route to a second unit in a house is a two-family dwelling, which the land use table permits by right in RD, RL, RH, CL, CH and UM, by conditional use in RC, PO and CG, and in RS only with Board of Zoning Adjustments approval (note 4); that is a duplex, not an ADU, and is not available in the RE, RA or RB single-family districts.

Ord. 14, 2025 adds no size, height or setback standard specific to ADUs. In both districts where ADUs are allowed, no fixed density or setbacks apply: the bulk and density of new structures is decided by the Architectural Review Board to fit the neighborhood (§4.404, §4.414), with setbacks for additions and accessory structures that meet existing setbacks approvable by staff. The district height limit is 45 feet (§4.405, §4.415). The definition does require the ADU to be 'smaller' than the single-family home it accompanies, with no ratio stated.

Neither the ADU definition nor the SH and SC conditional use listings require the owner to live on the property. Owner occupancy matters only for short-term rental: a nightly rental in an ADU counts as an owner-occupied short-term rental (permitted rather than conditional) when the main house on the same property is owner-occupied (Art. 3, SHORT TERM RENTAL - OWNER OCCUPIED). The board hearing a conditional use permit could attach conditions case by case, but the ordinance sets none.

Article 12 has no ADU row; its table requires 2.0 spaces per single-unit dwelling unit elsewhere. In the SC and SH districts, where ADUs are allowed, §12.012 lets adequate residential parking be provided on-street, in public or commercial lots, and says residential parking may be half what other districts require, so in practice about one space, which may be on the street. A short-term rental needs one space per rental contract (§19.154 I).

Every ADU needs a conditional use permit decided at a public hearing. Article 19 sends conditional uses to the Board of Zoning Adjustments under its general criteria (§19.01), while the SC text says the Architectural Review Board 'may grant conditional use permits' for the listed uses, and in both districts the ARB also reviews construction (a certificate of appropriateness). Ord. 14, 2025 adds no ADU-specific criteria, so the general §19.01 findings apply, followed by a building permit.

Nothing in the zoning text bars renting an ADU long-term; the city requires a $20 rental housing inspection before a tenant takes possession of any rental home or partial unit. Short-term rentals (under 30 days) must register yearly with Planning and Community Development, pay a $250 regulatory license fee per unit and pass a rental inspection (§19.154 K, M), and §19.154 P says a detached accessory structure may be a short-term rental only if it is a permitted detached ADU. An ADU short-term rental behind an owner-occupied main house counts as owner-occupied and is permitted in SH and SC (§4.402, §4.412); non-owner-occupied short-term rentals are conditional there and capped at 5 percent of dwelling units in SC and 8 units in SH (§19.154 Q, R; Ord. 22, 2024).