Durham, NC Accessory Structures: Garage Conversions (2026)

UDO § 5.4.2, Accessory Dwellings, governs converting a garage or other existing space within a Durham house into an accessory dwelling unit (ADU). The provision draws a sharp line based on method: detached ADUs must meet the maximum height allowed for accessory structures in the zoning district, and an ADU built as an addition to the primary structure must meet the height limit that applies to the primary structure itself. But the ordinance carves out a specific exception for interior conversions: 'Height limits shall not be considered if the accessory dwelling is only a conversion of existing space within the primary structure,' meaning a garage-to-ADU conversion that stays inside the existing building envelope does not have to be measured against either height standard.

Size limits still apply regardless of method. The heated floor area may not exceed 1,000 square feet if it is on a single story, or 1,200 square feet in total, except in the Residential Rural (RR) district on lots of four acres or larger, where the cap rises to 50% of the primary dwelling's heated floor area. In every case, the ADU's floor area can never equal or exceed that of the primary structure. A converted garage can also become a duplex-style two-unit ADU under the same primary residence, so long as the combined heated area of both units stays under 1,200 square feet.

The section was substantially rewritten by City-County Text Change TC18-07, 'Expanding Housing Choices,' which took effect in the City of Durham on October 28, 2019. Converted garages must still meet the NC Building Code and Housing Code, and no additional off-street parking is required for the new unit.