Moisture Planning Before Year Eight

Sooner or later, water gets into a house near the coast. Often nobody sees it for years, until a floor goes soft or a smell won't leave. A house that can drain and dry gives that water a way out.

Plan on water getting in

Seals age. Wind drives rain sideways into joints built for rain that falls straight down. Over the life of a house, water finds a way in somewhere.

So every wall should be able to do three things. It should drain the water, dry out afterward and stay open to inspection years later. How we plan for moisture starts there, for a new wall or a fifty-year-old one.

A wall that cannot dry will eventually tell you so.

Three ways water gets into a wall

Rain is the biggest. Roof overhangs, gutters, flashing and a drainage layer behind the siding send it back out. Grading moves it away from the foundation.

Humid air is the second. It slips through gaps, finds a cool surface inside the wall and turns to water there, out of sight. A continuous air barrier keeps it out.

Vapor is the third. It moves slowly through the materials themselves. Wall layers are chosen so the wall can dry in at least one direction.

Windows and doors are where water most often gets in. The order the flashing layers go on decides whether an opening drains or traps water, so that order is drawn and specified.

The crawlspace under an older house

Many older coastal houses sit over a crawlspace, the short open space between the ground and the first floor. Many were built before sealing a crawlspace was common practice.

A comfort problem upstairs can trace back to ground moisture rising from an open crawlspace below. So the fix often starts there. A performance retrofit can close and condition the crawlspace where the flood rules allow, and correct the drainage around the house.

In a mapped flood zone, an enclosed space below the flood height generally has to let floodwater in and out through openings. A sealed crawlspace there has to do that and still hold its air seal.

The year the house was built matters too. A house started before its town's first flood map is called pre-FIRM. Older houses like these are measured against today's flood rules once a renovation grows.

When the 50 percent rule applies

In a mapped flood zone, one rule shapes a big renovation. It is called the 50 percent rule, or substantial improvement.

The rule sets the cost of the work against the market value of the building alone, land left out. Repairs, remodeling and additions all count, added together.

Once the work reaches half that value, the whole house has to meet today's flood height, freeboard included. That holds even for rooms the work never touched. Carolina Beach draws its line at 49 percent.

Most towns count the work over any one year. New Hanover County's unincorporated areas, Burgaw and Boiling Spring Lakes count it over five.

Past the line, a renovation becomes an elevation project. On a low pre-FIRM cottage, replacing the house can be the better option. The assessment places the whole scope against your town's line before anything is priced.

Your air conditioner removes water too

A cooling system pulls water out of the air while it runs. An oversized one cools the house fast, shuts off and never runs long enough to dry the air. That is how a house reads 72 on the thermostat and still feels clammy.

Equipment sized to the house runs longer, so it controls humidity as well as temperature.

Keep the house easy to check

A moisture plan also has to work in year twelve:

• Key parts stay reachable, so a hunch can be checked without tearing anything open.
• Equipment, filters and drain pans get real room for service, because a part nobody can reach rarely gets looked after.
• The condensate line, the pipe that carries water away from the cooling coil, gets planned with care. A clogged one is a slow leak in a place nobody looks.
• You know the few spots on your house worth a look each season.

Own an older house near the water? Send us the address from our renovation page, and we'll tell you whether the flood rule limits your project.