Getting Ready for Moisture Season

Moisture season comes to the Triangle every year, and it often arrives faster than homeowners expect. By the time the air feels heavy in June, the crawl space under your house has usually been taking on moisture for weeks. Increased insect activity is often the first thing people notice, but that's just a nuisance. The real problem is the moisture accumulating under the home.

That moisture collects in the insulation and on the floor joists. When condensation is allowed to sit on structural wood through the humid months, year after year, it softens the wood, feeds mold and, given long enough, weakens the floor system.

Central North Carolina actually has two kinds of moisture problem, and they peak at different times of year: humid air in summer and wet ground in winter. Here is what each part of the year does to a crawl space in Wake and Durham counties, and what to check under the house as it comes around.

December Through February: Wet Ground

Winter air is drier, but winter ground is wetter. With the trees bare and temperatures low, far less of the rain that falls evaporates or gets drawn up by plants, so the soil stays saturated for longer. Piedmont soil is weathered rock with a clay-rich layer that drains slowly, and once it is full, water moving through it can come up through a crawl space floor or seep in at the base of the foundation wall.

What to check: standing water or wet soil after rain, a vapor barrier that has floated or puddled, mud lines on the piers, and, if you have a sump pump, whether it is running and discharging outside. Winter is also when the stack effect is strongest, pulling crawl space air up into the house, so a musty smell in January is worth taking seriously.

March and April: Spring Rain

The ground is often still wet from winter when the spring storms start. Gutters that filled with leaves in the fall, and with pollen and debris since, overflow and pour water down against the foundation.

What to check: clean the gutters, make sure downspout extensions are still attached and carry water well away from the house, and look for soil or mulch that has built up against the siding over the winter. If the crawl space took on water over the winter, this is the time to work out why, before summer humidity arrives on top of it.

May: Before the Humidity Arrives

Late spring is the best time to get ready for summer, while it is still comfortable to work under a house.

What to check: the insulation between the floor joists. If it is sagging or has fallen out, it was wet last summer and will be again. Make sure the vapor barrier covers all the soil and is not torn. If you have a crawl space dehumidifier, change the filter and confirm the drain line is clear before its busiest months. Atlantic hurricane season opens June 1, so test the sump pump now as well.

June Through August: Peak Humidity

This is moisture season proper. From June into September the outdoor air here routinely carries more moisture than a crawl space can hold at its cooler temperature. The ground keeps a crawl space cool, and the ductwork and cold-water pipes running through it are cooler still. In a vented crawl space, warm, humid air comes in through the foundation vents, meets those surfaces and condenses, like a glass of iced tea sweating on the porch.

This is when insulation gets heavy and starts to sag out of the joists. At that point its R-value has dropped and it is no longer performing at its intended rating, and wet insulation pressed against the subfloor keeps the wood above it damp too.

What to check: sweating ductwork, damp or sagging insulation, beads of water on joists or pipes, and a musty smell upstairs. Summer thunderstorms can drop a lot of rain in a short time, so look under the house after a hard downpour as well.

September and October: The Late-Summer Peak

The humidity hangs on into fall, and this is when a summer's worth of moisture tends to show. Hardwood floors over a damp crawl space often cup in late summer as the boards take on moisture from below. It is also the heart of the tropical season, when the remnants of a hurricane or tropical storm can bring days of heavy rain inland.

What to check: cupping or soft spots in the floors, and the crawl space after any big storm. By October a crawl space dehumidifier has done its hardest work of the year, so check its filter, its drain and the humidity reading. Our post on what cupping hardwood floors tell you about your crawl space explains how to read the floor.

November: Back Toward Wet Ground

As the leaves come down and the air dries out, the year turns back toward winter's wet ground.

What to check: clean the gutters once the leaves are down, test the sump pump, and make sure the end of any discharge line outside has not been buried by leaves or mulch.

Breaking the Cycle

Sagging, waterlogged insulation and condensation on the floor joists are early warning signs worth acting on before moisture season peaks. Opening more vents or adding fans tends to make a Triangle crawl space wetter in summer, not drier, because the air coming in is the problem.

The lasting fix is to take the crawl space out of the weather. Crawl space encapsulation seals the foundation vents, covers the soil and foundation walls with a sealed liner, insulates the walls and rim joist, and uses a dehumidifier to hold the humidity where mold and rot cannot get started. Any standing water from winter rain is dealt with first, because a sealed liner over a wet crawl space traps the water rather than keeping it out.

Triangle Reconstruction has been sealing and drying crawl spaces across Wake and Durham counties and every county bordering them since 2012. If your insulation is sagging or your ducts sweat in summer, call (919) 924-7600.