ADU Laws

Northern Virginia / Virginia (statewide trend)

Virginia adopted a statewide ADU framework effective January 1, 2025 (HB 900 / §15.2‑2292.2), defining ADUs and capping local permit fees, limiting minimum lot sizes, and allowing one ADU per single‑family lot, with optional local requirements on size (up to 1,500 sq ft or 50% of primary), lease terms, owner‑occupancy (either main or ADU), and distance from the main house. Localities like Fairfax, Arlington, and others still control details such as which residential zones permit attached or detached units, but they generally must treat ADUs as an accessory use and cannot require special‑use permits or extra parking beyond what the new statute allows.

Washington, DC

DC broadly permits “accessory apartments” in most R‑zones, often by right, including internal, basement, and some detached units, subject to lot size, height, and lot‑coverage rules, with a few zones still requiring a special exception review. The code also addresses entrance location, parking, and occupancy, but in practice many standard rowhouse and single‑family lots can add a code‑compliant ADU if general zoning and building standards are met.

Wilmington, North Carolina

Wilmington allows one ADU per lot in most residential zoning districts, typically up to 1,200 square feet or 50% of the main dwelling, whichever is less, with standard setbacks, height limits, and one off‑street space unless waived near transit. Detached backyard cottages, garage apartments, and interior conversions are all allowed as long as they meet the city’s development code and the NC Residential Code.

North Carolina (statewide)

North Carolina’s recent legislation (e.g., HB 409 / similar ADU preemption efforts) requires cities and counties that allow single‑family homes to also allow at least one ADU per lot, prohibits mandatory owner‑occupancy, and restricts localities from piling on extra parking or aesthetic standards beyond normal residential rules. Local zoning still sets maximum size, height, and placement, but the default posture is now ADU‑friendly statewide, preempting outright bans in most single‑family districts.

Charlotte, North Carolina

Under Charlotte’s Unified Development Ordinance, one ADU is allowed per single‑family lot, either attached or detached, with size tied to a percentage of the primary dwelling, and it must share ownership and utilities with the main house. The city regulates door placement, access, and parking but treats ADUs as an accessory residential use, so they are generally permitted where detached houses are allowed if basic dimensional standards are met.

Myrtle Beach, South Carolina

Myrtle Beach and Horry County rely on conventional zoning districts rather than a dedicated ADU statute, so small secondary units are typically only possible in multi‑residential or certain mixed‑use districts, or via planned developments, not in all standard single‑family zones. The city is also strict on short‑term rentals and subdivision rules, so using a “tiny home”‑style ADU as a rental or on a new small lot often runs into subdivision and STR restrictions rather than pure building‑code issues.

South Carolina (statewide)

South Carolina has no single statewide ADU mandate; instead, ADUs are allowed or restricted by local zoning, though model rules and guidance set typical limits such as max size of 1,000 sq ft or 50% of the main dwelling and a detached height cap around 25 feet. Many cities and counties that do allow ADUs require matching exterior appearance, detailed site plans, and sometimes owner‑occupancy or extra parking, so each jurisdiction’s ordinance must be checked before planning a project.

Georgia (statewide)

Georgia likewise leaves ADUs to local control, but many cities have started explicitly legalizing them in certain residential districts, with size caps, bedroom limits, and impervious‑surface controls. Urban jurisdictions like Atlanta often limit ADUs to around 750 square feet and impose owner‑occupancy and minimum lease‑term rules, while suburban and rural counties may be stricter or not address ADUs at all, effectively barring them in some zones.