Raleigh Accessory Dwelling Unit (ADU) Size Regulations
In the City of Raleigh, the maximum square footage for an Accessory Dwelling Unit (ADU) is generally capped at 800 or 1,000 square feet, depending on the size of the lot and the zoning district. Regardless of the numerical cap, the gross floor area of the ADU must always be less than the gross floor area of the principal dwelling on the lot [Section 2.6.3.D.1]. Furthermore, any ADU constructed as a manufactured home is strictly limited to a maximum of 600 square feet [Section 2.6.3.D.6].
Maximum Floor Area by District
The City of Raleigh Unified Development Ordinance distinguishes size limits based on whether the property is located in a Residential District or a Mixed Use District.
Residential Districts
For properties located in Residential Districts (R-1, R-2, R-4, R-6, and R-10), the City of Raleigh establishes maximum gross floor area (GFA) based on the total area of the lot.
| Lot Area | Maximum ADU Gross Floor Area |
|---|---|
| Greater than 40,000 square feet | 1,000 square feet |
| 10,000 to 40,000 square feet | 800 square feet |
| Less than 10,000 square feet | 800 square feet |
Note: The ADU must always be smaller than the principal dwelling, which may effectively lower these maximums for smaller primary homes [Section 2.6.3.G].
Mixed Use Districts
In the City of Raleigh Mixed Use Districts (including RX-, OX-, NX-, and CX-), the size of an ADU is standardized regardless of the lot size.
| District Type | Maximum ADU Gross Floor Area |
|---|---|
| All Mixed Use Districts | 800 square feet |
Note: As in Residential Districts, the gross floor area of the ADU must be less than the gross floor area of the total principal use [Section 3.6.2.G].
Specific Use Limitations and Exceptions
Manufactured Homes as ADUs
If a property owner in the City of Raleigh chooses to use a manufactured home as an ADU, specific additional requirements apply. The structure must be affixed to a permanent foundation and cannot exceed 600 square feet in gross floor area [Section 2.6.3.D.6].
Live-Work ADUs
In certain Mixed Use contexts, such as an Apartment building where a Live-Work use is located within an ADU, the floor area of the live-work space is further restricted. In these instances, the space cannot exceed 1,000 square feet or 40% of the gross floor area of the associated dwelling unit, whichever is smaller [Section 6.7.3.E.11].
General Accessory Structure Rules
While general accessory structures (like sheds or detached garages) in the City of Raleigh are subject to combined floor area limits based on lot size, the Raleigh Unified Development Ordinance explicitly exempts ADUs from these general accessory structure area limits. ADUs are governed specifically by the standards in their respective "Additional Housing Patterns" sections [Section 2.6.3.D.5].
Sections Cited
- Section 2.6.3. Accessory Dwelling
- Section 2.6.3.D. Accessory Dwelling Unit Regulations
- Section 2.6.3.G. Building Specifications (Residential)
- Section 3.6.2. Accessory Dwelling
- Section 3.6.2.D. Accessory Dwelling Unit Regulations
- Section 3.6.2.G. Building Specifications (Mixed Use)
- Section 6.7.3.E. Live-Work