Add an ADU to your lot

Your town decides what fits.

• Many towns allow one ADU per lot, and most cap how big it can be.
• Several beach towns have no ADU rule and decide lot by lot.
• On septic, the county health office often has to approve the system for a second home first.

Our lot check works from the address, and it can tell you three things about any of the four kinds below. We find out whether your town allows that kind of ADU, and how big. We look up your lot's flood zone. If the lot is on septic, a private tank and drain field, we tell you who has to approve a second home.

The kinds a town allows narrow the choice early. Carolina Beach recognizes an accessory apartment only inside the existing structure. In its residential districts, Calabash allows only a detached garage apartment, on the town's terms. Boiling Spring Lakes names a unit above a detached garage in its rule. Southport allows one within the house, attached to it or detached from it.

The patterns

Most of the rules fall into a few patterns. New Hanover County allows a detached ADU by right in districts that permit one: one per lot, beside a single-family house, with one parking space. That covers Masonboro, Ogden and Porters Neck. Pender County caps a detached unit at 33 percent of the main house's heated floor area, as in Rocky Point, Maple Hill and Currie. St. James allows one by special use permit, up to 800 square feet and two bedrooms, behind the main house. Burgaw caps an accessory apartment at half the main house or 800 square feet, whichever is less. Shallotte caps it at 35 percent of the primary house.

Southport lists an accessory dwelling as a special use in its R-10 and R-20 districts, decided at a Board of Adjustment hearing. Carolina Beach recognizes an apartment only inside the existing structure. Surf City allows one on the mainland and none on the island. Holden Beach, Caswell Beach, Ocean Isle Beach, Wrightsville Beach and Kure Beach set out no ADU category of their own. There, the answer comes lot by lot, from the town office that reads its code.

Where the code is silent

Where a town names no ADU, the question goes to the office that reads its code. In Ocean Isle Beach, that is the planning office. In Holden Beach, it is Planning and Inspections. In Caswell Beach, the zoning administrator decides, and in Kure Beach, it is the Building Inspector. We put the question to that office in writing, before any design assumes the answer.

What decides it on your lot

• Setbacks, lot coverage, and buildable area
• Whether the lot is on sewer or septic, and what capacity remains
• Electrical service capacity at the existing panel
• Driveway, parking, and emergency access
• Flood zone designation and required elevation
• Stormwater and drainage once impervious area increases
• HOA covenants and any architectural review
• Existing structure condition, where an ADU attaches to or sits above it

Bring us the address. That is where this starts.

In a mapped flood zone, the code limits enclosed space below the design flood elevation to parking, access and storage (Section R322.2.2). The design flood elevation is the flood height the code builds to. It is never lower than the base flood elevation, the flood height on FEMA's map. A garage below that line becomes living space only once the new floor sits at or above the height your town requires. That rule often decides between converting the garage and building above it.

Inland, the wastewater question usually comes first. Around Rocky Point and Maple Hill, Pender County Environmental Health has to approve capacity for a second home first. Only then does the zoning cap, a third of the main house, even matter. On Winnabow acreage, each home needs its own approved way to handle wastewater. In Castle Hayne, an ADU moves forward only once the county sees documented water and sewer capacity from the utility. Where the lot relies on a well and septic, those must meet the county's standards.

The answer is the same care a full house gets, scaled down. That means an air barrier that runs without a gap and ventilation sized to the small space. It also means dehumidification that runs long enough to work. Airtightness without stuffy interiors explains how a tight building pairs with fresh-air ventilation, and the high-performance page covers sizing the equipment correctly.

The six steps of our process walk through each stage in order, from that first conversation to the finished build.

For an ADU, the early steps answer one question first: what your lot and your town will allow. We confirm that with the jurisdiction in writing. Then we design against that record and estimate the cost in real time as the design develops. You finish holding a design you own, whether or not we build it.

Once the design and the permit path are settled, we direct the build, and certified trade partners work from the drawings. Your private client workspace holds the documents: each decision with its reasoning, your selections, and the build schedule.