Siding and exterior envelope replacement on the North Carolina coast

Code in force

2018 North Carolina Residential Code. New work meets the rules for a new structure (Section R102.7.1).

Design wind speed

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

New sheathing

Braced by one of the high-wind design methods the code lists for 130 mph and up (Section R301.2.1.1).

An opened wall

Insulated to code where the repair exposes the cavity, unless the cavity already holds insulation (Section N1110).

Building permit

None for siding replacement costing $40,000 or less and done to code. Load-bearing work needs one (General Statute 160D-1110).

Flood rule

In a mapped flood zone, 50 percent of the building's market value (49 in Carolina Beach). Most towns and counties count the work over one year. Some count two years or five.

Two parts of the code come into play once the wall is open. New sheathing has to be braced by one of the code's methods. Sheathing helps the wall stand up to wind, so it is part of the structure. And a wall cavity the repair leaves open gets insulated to today's code, unless it already holds insulation.

The permit follows the structure.

North Carolina exempts siding replacement from a building permit when the job costs $40,000 or less and meets the code. Work on load-bearing parts of the house needs a permit at any cost. We treat new sheathing and framing as that kind of work. So a job that re-sheathes the wall goes through a permit, and so does any job over $40,000, siding included.

The flood rule adds up the whole job.

In a mapped flood zone, the flood rule weighs the cost of the work against the market value of the building. Reach 50 percent, and the whole house has to meet the flood height a new house would. Carolina Beach sets its line lower, at 49 percent. Many towns count the work over any one year, and New Hanover County counts over five. Siding, sheathing and a roof on an older cottage can reach the line in one job. So we place the job against your town's line before we price it. The town-by-town table lists each rule.

A historic district reviews the outside first.

In some towns, a historic district reviews the outside of the house before the building permit. In the local district in Southport, exterior work needs a certificate of appropriateness, and it covers repair as well as new work. In Wilmington, exterior work in a local historic district needs one from the Historic Preservation Commission first.

Wind on this coast drives rain sideways, into laps and joints. Some water always gets past the siding. A wall lasts when that water has a path back out, and the wall has room to dry.

The layers, from the frame out

• Sheathing, repaired where it rotted and braced to the code
• A water-resistive barrier, each upper course lapped over the one below
• Flashing at every window and door, and where a roof meets the wall
• A rainscreen gap: a thin air space that lets water drain out and the wall dry
• An insect screen at the bottom of the gap, left open so water can leave
• Base flashing at the foundation, to throw water clear of the sill
• New siding and trim, with fasteners suited to salt air

Every opening gets flashed again.

Each window and door is flashed to its maker's instructions. Where those give no detail, the code calls for a pan under the sill, sloped or sealed so water runs back out. Every opening the job uncovers is flashed again before the new siding goes on. Replacing the windows and doors themselves is its own project, covered on our impact windows and doors page.

The siding has to hold in the wind.

The code asks the siding, the material behind it and its fastening to resist the wind loads for your house. That load depends on the design wind speed, the height of the house and how open the land or water around it is. So we match the siding and its nailing to that load.

Salt air decides the fasteners.

The code sets a corrosion area east of the Intracoastal Waterway, from the South Carolina line north to Beaufort Inlet. In our three counties, that means the barrier islands, such as Oak Island. There, metal fasteners and connectors outside the heated part of the house are hot-dip galvanized, or an approved equal. Siding nails and trim screws count. Coastal durability covers how we choose hardware for salt air.

You pick the siding.

You choose the siding and trim for their look and upkeep. Whatever you pick goes on over a wall that drains, and it is installed to its maker's instructions. How a coastal wall drains and dries goes deeper on the layers behind it.

Sealing air leaks while the wall is open

With the siding and sheathing off, the seams in the wall are easy to reach. If drafts, damp or high power bills are part of the problem, we can seal the air barrier then. We set an airtightness target, and a blower-door test checks the house against it. Whether to do it is your call.

Fasteners, flashing and the air barrier get checked while they are still in view, before the siding hides them.

We look hardest at the bottom of the wall.

On a house over a crawlspace, the wall stands on a sill plate and a rim joist. That is the wood where the frame meets the foundation wall. Water that gets behind old siding runs down the wall to that joint, so we look hardest there. A new sill plate on a masonry foundation is treated or naturally decay-resistant wood, as the code requires.

Hidden damage is priced as an allowance.

Some damage only shows once the siding is off. That damage is carried as an allowance in the price. The assessment records what can be seen before the work starts.

When the roof is part of the job

Sometimes the roof comes off in the same job, because it is near the end of its life or the damage runs up to it. The new roof meets the underlayment rule for your design wind speed. Under shingles at 140 mph and above, that means a heavier underlayment with wider laps. Every lot in Brunswick and New Hanover Counties is at 140 or above, and so is Topsail Township in Pender. Where the roof meets a wall, the flashing laps under the wall's water barrier and sends water onto the roof.

Living at home through the work

Staging is planned for each house, around the scope, the house and the weather. What has to stay usable, and when, is settled in the assessment, and the work is planned around it. Living through a renovation covers the rest.

Wall trouble can have more than one cause. A stain on the siding can trace back to a gutter, a roof edge or humid air leaking into the wall. The assessment looks at the structure, the envelope and the mechanical systems together, so the fix aims at the cause. Planning for moisture before it appears goes further into why.

The choices are yours.

• The siding and trim, for their look and upkeep
• Whether the windows and doors join the job
• Whether the roof joins the job
• Whether to seal the wall to an airtightness target, checked by a blower-door test

Design is its own step, and the drawings are yours to keep. Each decision goes into your private online workspace with the reason behind it.

Plan the whole envelope at once.

In a flood zone, everything done to the house inside your town's window counts together. A roof this spring and siding next winter can land in the same count. So we plan the whole envelope as one scope, and place it against the line before design commits you to it.

In Hampstead, many older houses along the sound were built before today's flood maps. Pender County counts its 50 percent line over any one year. A new roof and new siding in the same year count together there.