Maximum Size Standards for Accessory Dwelling Units (ADUs) in Charlotte
In the City of Charlotte, an Accessory Dwelling Unit (ADU) located within an accessory structure is permitted a maximum heated floor area of 600 square feet or 70% of the total floor area of the principal residential use, whichever is greater. Notwithstanding this calculation, the City of Charlotte mandates that no ADU may exceed a total absolute maximum of 1,000 heated square feet. These units must remain clearly subordinate to the primary residence and are limited to one per lot.
Size and Floor Area Requirements
The City of Charlotte Unified Development Ordinance establishes specific mathematical thresholds to ensure that an ADU remains incidental and subordinate to the principal dwelling. For ADUs situated within an accessory structure, the following area limits apply:
| Metric | Standard |
|---|---|
| Minimum Base Allowance | 600 heated square feet |
| Proportional Limit | 70% of the total floor area of the principal residential use |
| Calculation Method | The greater of the two values above is permitted |
| Absolute Maximum Cap | 1,000 heated square feet |
For example, if the principal residence in the City of Charlotte has a total floor area of 1,200 square feet, 70% of that area is 840 square feet. Because 840 is greater than the 600-square-foot base allowance, the ADU could be up to 840 square feet. If the principal residence is 2,000 square feet, 70% is 1,400 square feet; however, the absolute cap of 1,000 square feet would limit the ADU to that size [Section 15.6.F.6.a].
General Regulations for ADUs
Beyond square footage, the City of Charlotte imposes several requirements on the development and use of these units to maintain the residential character of the neighborhood:
- Subordination: Every Accessory Dwelling Unit must be clearly subordinate to the principal residential use [Section 15.6.F.1].
- Quantity: Only one ADU is permitted on any single lot [Section 15.6.F.3].
- Ownership: The ADU and the associated principal dwelling must remain under the same ownership [Section 15.6.F.4].
- Structure Type: ADUs are permitted in conjunction with single-family dwellings in any district where they are allowed, and with duplex dwellings provided the duplex units are not located on sublots [Section 15.6.F.2].
- Accessory Structure Compliance: If the ADU is a detached building, it is also subject to the general accessory structure regulations of the City of Charlotte, including height and setback requirements [Section 15.6.F.6.b].
Sections Cited
- Section 15.3 Use Definitions
- Section 15.6.F Dwelling – Accessory Unit (ADU)
- Section 17.1 General Standards for Accessory Structures