Room additions and primary suites on the North Carolina coast

The assessment puts the house on record before anything is priced. Design comes next as its own step, and the drawings are yours to keep. Your private online workspace keeps each decision next to its reason.

How an addition goes together

You make the choices.

• What the room is for: a bedroom, a family room, an office or a primary suite
• Which side of the house it goes on, inside the lot's lines
• A roof that carries on the old roofline, or a shape of its own
• Where the doorway into the house goes
• Heating and cooling from the house's system, or a system for the room
• Windows, siding and trim to match the house
• For a suite: a shower or a tub, the closet and the finishes

A bonus room over your garage wing is built on top of the garage, so it is planned with our second-story additions.

Rot in the old wall is priced as an allowance.

Opening the old wall for the doorway can uncover rot or soft framing behind it. Damage that only comes to light then is carried as an allowance in the price.

You can stay home while it is built.

Your household stays in the house during a room addition. The doorway into the house is cut once the new room is closed in. Living through a renovation covers how the work is planned around you.

Code in force

2018 North Carolina Residential Code. The addition meets the rules for a new structure. The house can stay as built, as long as the work leaves it safe and performing as before (Section R102.7.1).

Design wind speed

Brunswick and New Hanover: 140 mph west of US 17 and 150 mph east of it. Pender: 130 mph, apart from Topsail Township at 140 west of the Intracoastal Waterway and 150 east (Table R301.2(4)).

Building permit

Always. An addition is new load-bearing structure, so the $40,000 permit exemption never reaches it (General Statute 160D-1110).

Moving in

Once the inspector issues a certificate of compliance after the final inspection (General Statute 160D-1116).

Septic lots

An added bedroom goes to the county health department first. The building permit waits for its approval (General Statute 130A-338).

Waterfront lots

State coastal rules cover at least the first 75 feet back from a sound or tidal creek. On the oceanfront, the state's ocean setback governs (15A NCAC 07H).

Setbacks and coverage set the size.

Your zoning district sets how close the room can come to each lot line, and how much of the lot buildings can cover. In the main R-1 district on Holden Beach, the setbacks grow and the coverage cap drops once a house reaches 4,000 square feet. Carolina Beach asks for an impervious coverage plan when a project adds more than 325 square feet of impervious surface. In Southport, any change to the footprint needs a minor site plan.

Some older houses already sit closer to a lot line than today's zoning allows. Brunswick County and St. James hold the enlargement of such a house to today's setbacks, unless a variance is granted.

On the water side of the lot

Along a sound, a tidal creek or many canals, the state's coastal rules cover the first 75 feet back from normal high water. New building sits at least 30 feet from the water, with a few exceptions written into the rule. Hard surfaces, the house included, are capped at 30 percent of that strip. A design can go past the cap only by showing it protects the water as well. Beside Outstanding Resource Waters, such as Masonboro and Topsail Sounds, the strip runs 575 feet deep and the cap is 25 percent.

On the oceanfront, the state's setback is measured inland from the vegetation line, or from a line the state fixed in its place. It grows with the size of the house and the beach's erosion rate, and an addition has to meet it. Where the old house sits closer than today's line, a new room behind the line can join it in looks only, with no structural tie.

A marsh-front or creek-front lot in Scotts Hill often falls under these rules. On a lot like that, the street side or a side yard can have more room to give.

A historic district reviews the addition first.

In Southport's local historic district, a certificate of appropriateness comes before the building permit, and it covers additions. In Wilmington's local historic districts, an addition needs the Historic Preservation Commission's approval first. The commission looks at the outside. State law gives it no say over the rooms inside, apart from a landmark whose owner has consented to interior review.

A house built before 1978

A house built before 1978 falls under North Carolina's lead-safe renovation rules. On an older house, materials that may hold asbestos are checked by an NC-accredited inspector before demolition. Those include old flooring and its glue, joint compound and ceiling texture. Older houses covers what else a house's age can change.

Every lot here is in the high-wind zone.

Design wind speeds run from 130 to 150 mph across Brunswick, New Hanover and Pender Counties. At 130 mph and up, the code sends the design to one of its high-wind methods (Section R301.2.1.1). So the room is tied down in one unbroken chain, from the rafters through the walls to the foundation. Where it meets the house, the joint is engineered for the wind at your address.

East of the Intracoastal Waterway, metal connectors and fasteners outside the heated part of the house are hot-dip galvanized, or an approved equal. Coastal durability explains how salt air shapes the hardware we pick.

The new footing goes in beside the old one.

On a crawl space or slab house, the new room gets a footing of its own. At 140 and 150 mph, the code puts every outside wall on a continuous concrete footing (Section R4503.1). Digging beside the house must leave the old footing supported, so it is shored or protected while the trench is open (Section R403.1.9).

We also build additions onto raised island houses on pilings. An addition there must be engineered for that house.

Where the room meets the house

The doorway into the house is cut through the old outside wall. Where that wall holds up the roof, a header spans the opening and carries the load around it.

In a mapped flood zone, the addition counts toward your town's 50 percent rule. In many towns, a room joined by a doorway alone, or standing on its own bearing wall, meets the flood rules on its own. Frame it into the old house, or build in a V zone, and crossing the line brings the whole house to today's flood height.

Where the new roof meets the old one

The new roof can carry on the old roofline, or take a shape of its own, such as a lower shed roof. That choice is yours. Either way, the new roof is tied down for the wind at your address.

Where the new roof meets the old roof or wall, rain looks for a way in. So the code asks for flashing wherever a roof meets a wall or changes slope (Section R903.2.1). Each piece laps over the one below it, in the order water runs. A low-pitched shed roof under shingles gets a double layer of underlayment (Section R905.2.2).

New walls meet today's energy code.

The new walls, roof and floor meet the energy code's insulation and air-sealing rules for a new house (Section N1108). Behind the siding, a water barrier covers the frame, and every window and door is flashed. Siding and envelope replacement shows how a coastal wall is built to drain and dry.

On the barrier islands, glass in the new room needs protection from flying debris. Impact windows and doors covers the ratings. Planning for moisture before it appears goes further into keeping new walls dry.

Heating and cooling for the new room

The code bars an addition from overloading the systems it joins. New heating and cooling equipment is sized from a load calculation. If the room takes ducts from the old system, that system is evaluated for the new design (Section N1108.1.1.2). HVAC design explains why an oversized system leaves a coastal house clammy.

Every bedroom needs a way out.

Each bedroom needs at least one window or door big enough to climb through in an emergency (Section R310.1). It opens onto a yard or straight onto the street. The code calls it an emergency escape and rescue opening: a way out for you, and a way in for rescuers.

The whole house gets smoke alarms placed to today's rules.

A permitted addition, or any added bedroom, means smoke alarms placed as in a new house (Section R314.2.2). Each bedroom gets one, the area just outside the bedrooms gets one, and so does every level of the house. Carbon monoxide alarms come along where the house burns fuel, such as a gas range or fireplace. An attached garage that opens into the house calls for them too.

On septic, bedrooms size the system.

North Carolina sizes a septic system by its bedrooms. So an added bedroom goes to the county health department first, and the building permit waits for its approval. The tank and drain field also limit where the room can sit. That check is part of adding on in places like Winnabow, Maple Hill and Boiling Spring Lakes, where many houses run on septic.

An addition that adds no bedroom can go to the permit with the state's existing-system affidavit. The owner signs it to confirm the work keeps the required distance from the septic system.

A primary suite adds a bath.

A primary suite is a bedroom, a closet and a bath for your own household. The bath is built as in a bathroom remodel. A waterproof layer goes behind the tile, and a tiled shower floor is water-tested before the tile goes on. The fan is ducted outdoors, and the walls are sealed so damp air stays out of them.

Add a kitchen, and it becomes an in-law suite.

A suite with its own kitchen or its own outside entrance is an in-law suite, and our in-law suite page covers it. With a kitchen, the suite has everything the code counts as a home of its own: places to live, sleep, eat, cook and wash. Your town's rules for accessory dwelling units then apply.