Columbia, SC Accessory Structures: ADU Owner Occupancy (2026)

The owner-occupancy condition sits inside the same accessory dwelling unit standard that authorizes a second unit on a single-family lot, Sec. 3(d)(1), and it is the second listed condition after the one-ADU-per-lot cap. It gives the property owner two compliant configurations, not one: the owner can live in the principal house and rent the ADU, or live in the ADU and rent the principal house, but at least one of the two units on the lot must be the owner's permanent, full-time residence at all times.

A lot where neither unit houses the owner, for example, a property bought purely as a rental with both the house and the ADU leased to tenants, does not meet the standard even if every other ADU requirement, size cap, parking, single kitchen, is satisfied. The requirement works together with the rest of Sec. 3(d)(1): the ADU must share the principal dwelling's address and cannot be subdivided or separately owned, so ownership of the lot, and therefore of both units, stays unified, which is what makes the owner-occupancy test enforceable against a single owner rather than two separate landlords.

The standard does not specify a minimum number of months of occupancy or require an annual affidavit; it reads as a continuing condition of the ADU's legal status. Practically, a homeowner who moves out of both units, for instance relocating for work and renting out the whole property, converts the ADU from a code-compliant accessory unit to a non-compliant one until an owner resumes residency in the house or the ADU.