Accessory Structures in Onslow County, NC (2026)
2 rules for unincorporated Onslow County, North Carolina.
Verified from official government sources
ADU Rules
Onslow County allows one accessory dwelling unit per lot with a single-family home in the unincorporated county. Its heated floor area is capped at 60 percent of the principal home's heated area, or 900 square feet, whichever is less in the R-15 and R-20 districts, and 1,200 square feet in the Rural Agricultural (RA) district.
Onslow County ADU and Garage Apartment Rules
Some RestrictionsOnslow County Code of Ordinances § 9.8(A)
A.ACCESSORY DWELLING UNIT 1.One accessory dwelling unit is permitted per lot that contains a single-family dwelling. 2.The heated gross floor area of the accessory dwelling may not exceed 60 percent of the heated gross floor area of the principal dwelling, or 900 square feet, whichever is less in the R-15, and R-20 zoning districts, or 1,200 square feet in the RA (Rural Agricultural) zoning dis...
Shed & Carport Rules
A detached shed in Onslow County is a residential accessory structure under Section 8.3. Enclosed accessory buildings cannot exceed 50 percent of the principal home's square footage without a Special Use Permit, must sit behind the front building line except on lots of 2 acres or more, and follow size-based setbacks in Table 8-3.
Onslow County Shed Size and Setback Rules
Some RestrictionsOnslow County Code of Ordinances § 8.3, Table 8-3, Note 1
The total square footage of enclosed accessory structures shall not exceed 50 percent of the total square footage of the principal structure and will not apply to pools and decks. This limitation does not apply in the RA (Rural Agriculture) Zoning District. If the accessory structure is to be over 50 percent, then it shall require a Special Use Permit.
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