Durham’s Unified Development Ordinance gives ADUs a separate use and size rule, while also restricting where a unit may be located. Check mapping before applying the numerical cap.
Local standards
The selected local standards are summarized in the Durham Unified Development Ordinance §5.4.3 — Accessory Dwelling. The UDO lists a standard maximum of 1,000 square feet for a single-story unit or 1,200 square feet total for a multistory unit. In Rural Residential districts on lots of at least four acres, it allows up to one-half the principal dwelling’s floor area, while still requiring the ADU to remain smaller than that dwelling.
Confirm the applicable rule
The cited code provision bars ADUs in mapped flood-hazard areas. Height and placement follow additional underlying district standards that are not reproduced here. Confirm current UDO text, Rural Residential lot area, principal-unit measurement, zoning map, and official flood-hazard mapping; a dimensional cap does not override the location rule. Zoning measurements do not by themselves establish fire separation, building-code compliance, utility capacity, or permit approval. For shared measurement methods, see the setback and separation guide and floor-area guide.
