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Accessory dwelling units in North Carolina

An accessory dwelling unit is a second, self-contained home on the same lot as a main house. No enacted North Carolina statute sets general rules for one, so the local ordinance decides the size, count, and location. The lot must also show room, wastewater capacity, and a record with no restriction against it.

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Quick summary: This guide explains what an accessory dwelling unit is, what North Carolina law says about one, and which rules a local ordinance sets. It is for owners, infill builders, and investors who want a second home on one lot. The key takeaway: the town or county ordinance decides, and the lot must show room, wastewater capacity, and no recorded restriction against a second dwelling.

What an accessory dwelling unit is

An accessory dwelling unit (ADU) is a second, self-contained home on the same lot as a main house. Raleigh’s ordinance defines it as a self-contained dwelling unit on the same lot as a principal dwelling. It can be detached, attached, inside the house, or above a garage.

Durham’s ordinance describes a dwelling that is part of a principal dwelling or on the same lot, and smaller than it. Common names for the same thing include garage apartment, backyard cottage, in-law suite, and basement apartment.

An ADU stays part of the main lot. It is not a separate lot, and Raleigh bars a transfer of its ownership apart from the main house. To sell the second home on its own, you need a new lot. See Lot split: can you split your lot.

What North Carolina law says

No enacted North Carolina statute sets general rules for accessory dwelling units, so the local ordinance decides. Bills to change that have been filed. House Bill 627 of the 2025-2026 session would have added a new section on ADUs to Chapter 160D. Its last recorded action, on May 7, 2025, sent it back to a House rules committee. The section number it proposed is still reserved for future codification.

State law covers one narrow case. A temporary family health care structure is a permitted accessory use on lots zoned for single-family detached homes. The statute limits it in four ways:

  • Occupant. One mentally or physically impaired person, cared for by a relative or a legal guardian who lives on the property.
  • Size. No more than 300 gross square feet.
  • Foundation. It may not sit on a permanent foundation.
  • Removal. It comes off the lot within 60 days after the care ends.

That structure is temporary. A permanent ADU still follows the local ordinance. Ask planning staff whether a new state law is in effect when you apply.

The rules a local ordinance sets

A local ordinance sets the ADU’s count, size, location, and parking. Two adopted ordinances show how much the rules vary.

Rule Raleigh, Sec. 2.6.3 Durham, Sec. 5.4.2
Where allowed R-1, R-2, R-4, R-6, and R-10 districts A residential lot with one or two primary dwelling units
How many One, or up to two in a Frequent Transit Area One
Size cap Smaller than the main house. 1,000 square feet on lots over 40,000 square feet, 800 square feet on smaller lots Smaller than the main house. 1,000 square feet on a single story, 1,200 square feet in total
Height 26 feet The accessory structure height limit, for a detached unit
Parking No vehicle minimum and no maximum in the parking table No parking required
Other limits Not on a flag lot. At least 6 feet from other buildings. A lockable outside entrance Not in a special flood hazard area or a future conditions flood hazard area. No travel trailer or RV as an ADU

The two cities differ on size, location, and flood rules. Your town can differ from both. Read the section for your district before you draw a plan.

Owner occupancy

Some ordinances require the owner to live in the main house or the ADU. Neither section in the table states that rule. Read your town’s section, and ask planning staff before you plan to rent both units.

Private restrictions

A recorded covenant or owners association declaration can bar a second dwelling that the zoning allows. Neighbors or the association enforce it, not the town. See Restrictive covenants: what they are and how to find them.

Watch for: A lot on septic can meet every zoning rule for an ADU and still fail on wastewater. Ask the local health department before you pay for plans.

Septic and sewer capacity

Wastewater capacity often decides whether an ADU can go on the lot. On septic, the permit sizes the system by bedrooms. State rules set the minimum design daily flow for a dwelling unit at 120 gallons per day per bedroom. An operation permit stays valid only while the design daily flow stays unchanged.

An ADU adds bedrooms, so the health department reviews the system first. The existing drainfield and its repair area may not have room for the added flow. On public sewer, ask the utility about a second connection and a meter. See Sewer, septic, or a package plant.

What the lot must show

The lot must show room, utilities, and a clean record before an ADU is worth a design fee. Check these items in order.

  1. Zoning district. Confirm that the district allows an ADU, and read its size, height, and setback rules.
  2. Lot area and shape. Lot area sets the size cap in Raleigh. A flag lot bars an ADU there. See Flag lot: what it is and when a town allows one and Minimum lot size: what it is and how to find it.
  3. Setbacks. A detached ADU in Raleigh sits at or behind the front wall of the house. Side and rear setbacks are 5 feet on lots of 40,000 square feet or less, and 10 feet on larger lots.
  4. Flood zone. Durham bars an ADU in a special flood hazard area.
  5. Wastewater. Septic capacity for the added bedrooms, or a sewer connection.
  6. Covenants. No recorded restriction against a second dwelling.

Take action: Send the lot’s address and the ADU you have in mind, and get the zoning, flood, and wastewater questions in order. Start with Can the house you want fit on this lot?

Who answers the question

Planning staff answer the zoning question. Other parties answer the rest.

  • Building inspections permits the ADU under the state building code. Durham notes that an ADU must meet all building and housing codes.
  • The local health department decides whether the septic system can take the added bedrooms.
  • The water and sewer utility answers questions about connections and meters.
  • A North Carolina real estate attorney reads the covenants and the owners association documents.
  • A licensed land surveyor prepares the site plan that shows the setbacks.

The public record shows the zoning district, the lot lines, the flood zone, and any recorded covenant. It does not show the septic system’s real capacity. We read the record in a fixed order and hand you the open questions.

Key recap

  • An ADU is a second, self-contained home on the same lot as a main house. It is not a separate lot.
  • No enacted North Carolina statute sets general ADU rules. The local ordinance decides.
  • Raleigh and Durham set different size caps, counts, and flood rules. Your town can differ from both.
  • On septic, an ADU adds bedrooms, so the health department reviews the system first.
  • A recorded covenant can bar an ADU that the zoning allows.

Questions

Does North Carolina allow accessory dwelling units?

North Carolina has no enacted statute that requires or bars them in general. Each town or county decides in its ordinance. Raleigh and Durham both allow them in residential districts, with different limits.

Can I sell an ADU separately from the main house?

Usually not. Raleigh bars a transfer of an ADU’s ownership apart from the main house. To sell the second home on its own, you need a new lot through a subdivision or lot split.

Do I need a separate septic system for an ADU?

Not always. The health department decides whether the existing system can take the added bedrooms. If it cannot, the system needs an upgrade or the ADU needs another wastewater option.

Do I need parking for an ADU?

It depends on the ordinance. Durham requires no parking for an accessory dwelling. Raleigh’s parking table sets no vehicle minimum for an ADU.

References

Primary sources cited on this page, in APA style.

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