Franklin County, NC Accessory Structures: ADU Rules (2026)

The Unified Development Code's Accessory, Temporary, and Home Occupation Use Group standards at § 5.3.10, item 2, cap accessory dwelling units at one per lot, and only where the lot is developed with a single dwelling unit; a residential lot already carrying more than one unit cannot add an ADU, and no ADU is permitted on a lot with a two-family duplex, multi-family building, or family care home. The unit must meet every setback that applies to accessory uses, buildings, and structures elsewhere in Article 5, plus a 20-foot separation from the principal dwelling, and it cannot use a separate driveway from the main house.

If the lot's legal access runs over an easement, a recorded maintenance agreement for that easement is required. Franklin County's Environmental Health Department must certify that any septic system serving the property can handle the added unit before it is approved. An ADU may be a manufactured home, but only if it satisfies every other criterion in the section and the underlying zoning district allows manufactured housing. Because the standard sits in the UDC, violations, building an unpermitted second unit, skipping the septic certification, or ignoring the 20-foot separation, run through the Administrator's notice-and-correction process at § 3.3 and can draw a civil penalty up to $500 per day or a Class 3 misdemeanor charge under § 3.4.2, in addition to permit denial or revocation for the underlying development approval.