ADU rules in Lexington

Detached ADUs are an accessory use by right in the R-1A through R-1E, R-1T, R-2, R-3 and R-4 zones and the Expansion Area EAR zones, on a lot with a single-family dwelling. The 2021 ordinance (Ord. 102-2021) allowed only conversions of existing accessory structures for a pilot period; Ord. 148-2023, adopted December 7, 2023, allowed newly built detached ADUs, and Sec. 3-12 now lets an ADU be created through new construction. A modular or manufactured home on a permanent foundation may serve as the ADU. The R-5 zone's accessory-use list omits ADUs, and the agricultural zones use farm employee dwelling units instead.

Attached ADUs (converted living space, attached garages, basements, attics or additions) are allowed by right in the same zones as detached units. An attached ADU follows the underlying zone's floor area ratio, lot coverage, yard and height rules for a principal structure, may not add a second pedestrian entrance on the primary wall plane, and any exterior stairs serving it must be on the side or rear.

Sec. 3-12 caps every ADU at 800 square feet, except that converting an existing basement has no size limit as long as it stays within the structure's footprint. Attached units take the underlying zone's height, FAR and lot coverage. Detached units are accessory buildings under Sec. 15-6: all accessory buildings together may not exceed 50 percent of the principal building's square footage or 625 square feet, whichever is greater, nor its footprint, and may not exceed the principal structure's elevation or 20 feet at mid-gable; the city's handout gives the detached range as 625 to 800 square feet depending on the house. There is no minimum lot size and only one ADU per lot.

No owner occupancy requirement. The 2021 ordinance required the owner to live in one of the two units and record a deed restriction; Ord. 148-2023 (December 7, 2023) removed both, and the current Sec. 3-12 contains no residency or deed-restriction clause. Occupancy of the ADU itself is capped at two persons plus children related to either of them or in their custody. Hosting an ADU as a by-right short-term rental still requires a primary resident on the property (see rentalRestrictions).

No additional off-street parking is required. Lexington's zoning ordinance has carried no residential parking minimums since the 2022 parking overhaul (Ord. 113-2022), and Sec. 3-12 instead allows one additional space for an ADU in a zone with a parking maximum, such as the Infill and Redevelopment Area cap of two spaces per single-family lot. The city's handout states that no additional parking space is required.

Administrative. The applicant must hold a pre-application conference with the Division of Planning five working days to three months before applying, then obtain an ADU zoning compliance permit from the Division of Planning, which must issue before the Division of Building Inspection releases the building permit. No Board of Adjustment hearing is needed for the ADU itself; H-1 historic and ND-1 neighborhood design overlays can add review or standards.

Long-term rental of either unit is allowed now that owner occupancy is gone; the ADU is limited to two persons plus related children. Every short-term rental (under 30 days) needs a Division of Revenue special fee license (Code of Ordinances Sec. 13-77), and on single-family lots in residential zones only one dwelling unit or one ADU may be a short-term rental. A hosted rental (a primary resident living on the property, 275 days a year) for up to 10 guests is an accessory use; un-hosted rentals need a Board of Adjustment conditional use permit, at least 600 feet from other conditional-use STRs and within a 2 percent cap on un-hosted units within 1,000 feet. A detached accessory structure may be a short-term rental only if it is a permitted detached ADU or farm employee dwelling unit.