Accessory Dwelling Unit (ADU) Regulations in the City of Raleigh
In the City of Raleigh, an Accessory Dwelling Unit (ADU) is a self-contained residential unit located on the same lot as a principal dwelling. Generally, property owners are permitted to build one ADU (or up to two in designated Frequent Transit Areas) provided the unit is smaller than the primary residence, does not exceed 26 feet in height, and is situated at or behind the front wall of the main house [Section 2.6.3.C, Section 2.6.3.D].
Permitted Locations and Quantity
Accessory Dwelling Units are allowed as an accessory use to Single-unit, Two-unit, and Multi-unit living in the following City of Raleigh zoning districts: R-1, R-2, R-4, R-6, R-10, RX-, OX-, NX-, and CX- [Section 6.1.4].
- Standard Allowance: Typically, only one ADU is permitted per lot [Section 2.6.3.D.2].
- Frequent Transit Areas: On lots within a Frequent Transit Area (as mapped in the Comprehensive Plan), up to two ADUs are permitted. However, only one of these units may be attached to the principal building [Section 2.6.3.D.2].
- Townhouses: In townhouse developments, only one ADU is permitted per townhouse lot, regardless of whether the property is in a Frequent Transit Area [Section 2.6.3.D.2].
- Prohibited Locations: ADUs are expressly prohibited on Flag Lots [Section 2.6.3.D.9].
Dimensional and Size Standards
The City of Raleigh regulates the size of an ADU based on both the size of the principal dwelling and the total area of the lot. The gross floor area of the ADU must always be less than the gross floor area of the total principal dwelling [Section 2.6.3.D.1].
Maximum Floor Area and Height
| Lot Size | Maximum Gross Floor Area (GFA) | Maximum Building Height |
|---|---|---|
| Greater than 40,000 sq. ft. | 1,000 sq. ft. | 26 feet |
| 10,000 to 40,000 sq. ft. | 800 sq. ft. | 26 feet |
| Less than 10,000 sq. ft. | 800 sq. ft. | 26 feet |
Note: GFA includes all conditioned space. Attached unconditioned space is included in the calculation of accessory structure floor area [Section 2.6.3.G, Section 2.6.3.I].
Required Setbacks for Detached ADUs
| Setback Type | Lot > 40,000 sf | Lot 10,000 - 40,000 sf | Lot < 10,000 sf |
|---|---|---|---|
| From Primary Street | Must be at or behind the front wall of the house | Must be at or behind the front wall of the house | Must be at or behind the front wall of the house |
| From Side Street | 20 feet | 20 feet | 10 feet |
| From Side Lot Line | 10 feet | 5 feet | 5 feet |
| From Rear Lot Line | 10 feet | 5 feet | 5 feet |
| From Alley | 4' (no parking) / 20' (with parking) | 4' (no parking) / 20' (with parking) | 4' (no parking) / 20' (with parking) |
Note: For townhouse lots, side and rear setbacks apply to the site boundary [Section 2.6.3.H].
Building and Operational Requirements
- Foundation: ADUs must be affixed to or constructed on a permanent foundation. They cannot be moveable structures [Section 2.6.3.D.1.b].
- Access: The unit must be accessed via a lockable external entrance. All entrances must be externally accessible by pedestrians from the driveway, street, or alley serving the lot [Section 2.6.3.D.3, Section 2.6.3.D.8].
- Separation: Unless attached by a common wall, a detached ADU must be separated from any other building on the lot by at least 6 feet [Section 2.6.3.D.7].
- Parking: The City of Raleigh does not require additional off-street vehicle parking for an ADU [Section 7.1.2.C].
- Ownership: Ownership of an ADU cannot be transferred separately from the principal dwelling unit [Section 2.6.3.D.4].
- Use: Only residential uses are permitted, with the exception of a "Live-Work" use, provided it is the only Live-Work use on the lot and meets all other accessory use definitions [Section 2.6.3.C].
Manufactured Homes as ADUs
A manufactured home may serve as an ADU if it is no greater than 600 square feet and meets specific City of Raleigh design standards, including [Section 2.6.3.D.6]:
- A predominant roofline pitch of 5:12 or greater.
- Eave projections of at least 10 inches.
- A minimum first-story exterior wall height of 7 feet, 6 inches.
- Non-reflective exterior wall coverings.
- Foundation skirting made of brick, stone, or consistent siding materials.
Sections Cited
- Section 1.5.3 Outdoor Amenity Area
- Section 2.1.3 Additional Housing Patterns
- Section 2.6.3 Accessory Dwelling (Residential Districts)
- Section 3.6.2 Accessory Dwelling (Mixed Use Districts)
- Section 6.1.4 Allowed Principal Use Table
- Section 7.1.2 Required Parking
- Section 12.2 Defined Terms