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Where Crawl Space Moisture Comes From

Moisture gets into a crawl space four ways, and many homes have more than one at once:

  • Liquid water. Rain runoff, poor grading, clogged gutters and a high water table put water on or under the ground.
  • Ground vapor. Bare soil gives off water vapor all the time.
  • Humid air. Open foundation vents let warm, humid North Carolina air in, and it condenses on cool surfaces.
  • Leaks and condensation. Plumbing leaks, sweating ducts and dryer or bath vents that end in the crawl space add water.

Fix It in the Right Order

Moisture control works best as a sequence. Skipping a step usually means the next one fails.

  • 1. Water outside the house. Clean gutters, extend downspouts and fix grading so water runs away from the foundation.
  • 2. Liquid water in the space. If water collects, install drainage or a sump pump.
  • 3. Leaks. Repair plumbing leaks and route dryer and bath vents outside.
  • 4. Ground vapor. Cover the soil with a heavy vapor barrier.
  • 5. Humid air. Seal the vents and gaps; this is the step that makes the space a sealed system. See crawl space encapsulation.
  • 6. Remaining humidity. Add a dehumidifier to hold the humidity in a safe range.

Signs of a Crawl Space Moisture Problem

  • A musty or earthy smell in the house, stronger on humid days or after rain
  • Standing water or damp soil in the crawl space
  • Sagging, dark or wet insulation under the floor
  • Mold or mildew on joists, subfloor, ducts or the foundation
  • Condensation on ducts, pipes or the underside of the floor
  • Floors that feel cold, soft or bouncy, or gaps between the floor and baseboards
  • Pests such as termites, roaches or rodents, which like damp spaces

What You Can Do Right Now

While you plan a fix, these steps cost little and help:

  • Clean gutters and extend downspouts several feet from the foundation.
  • Make sure the ground slopes away from the house.
  • Route dryer and bath exhaust vents outside, not into the crawl space.
  • Fix visible plumbing leaks and insulate cold water pipes that sweat.
  • Keep stored items out of the crawl space.
  • Take a flashlight and look at the insulation and the ground after heavy rain.

Why It Matters

A damp crawl space does not stay in the crawl space. Air flows upward through gaps in the floor, a pattern often called the stack effect, so a share of the air you breathe at home came from under the house. Moisture also weakens the framing over time, invites termites and wood rot, and can make heating and cooling less efficient.

Fixing moisture is usually much cheaper than repairing the damage it causes.

Our Moisture Control Process

We start with an inspection of the crawl space, the grading and the gutters, then tell you what is wrong and in what order to fix it. You get a free estimate for the full plan or for each step. We only recommend what your space needs; a dry crawl space with a small humidity issue may need a dehumidifier and nothing more.

If mold is already present, we remove it before sealing. See mold removal in Raleigh.

Cost

Costs depend on which steps your crawl space needs. Full encapsulation typically costs $3,500 to $7,500 for Triangle homeowners, with a range of $1,500 to $15,000. Sump pump installation typically ranges from $900 to $2,500. Mold remediation ranges from about $500 for small areas to $6,000 or more for extensive growth, and most homeowners pay $1,500 to $3,500.

We offer flexible financing options for qualifying homeowners. Terms depend on the lender and your approval.

Crawl Space Moisture Control by City

Pick your city for local information and a free estimate.

Crawl Space Encapsulation Apex, NC
Crawl Space Encapsulation Cary, NC
Crawl Space Encapsulation Charlotte, NC
Crawl Space Encapsulation Clayton, NC
Crawl Space Encapsulation Concord, NC
Crawl Space Encapsulation Fuquay-Varina, NC
Crawl Space Encapsulation Garner, NC
Crawl Space Encapsulation Holly Springs, NC
Crawl Space Encapsulation Knightdale, NC
Crawl Space Encapsulation Raleigh, NC
Crawl Space Encapsulation Wake Forest, NC
Crawl Space Encapsulation Zebulon, NC

Also see: Vapor barrier installation, Crawl space dehumidifiers , sump pump services and mold removal.

Crawl Space Moisture Control: Frequently Asked Questions

Rain runoff and poor grading, a high water table, ground vapor from bare soil, humid air through open vents, and leaks or condensation. Many homes have more than one cause.

Work from the outside in: gutters and grading, then drainage or a sump pump if water collects, then a vapor barrier, sealed vents and a dehumidifier. We inspect and tell you which steps your space needs.

It can contribute to musty odors and mold, and air moves from the crawl space into the house. If anyone at home has allergies or asthma, a damp crawl space is worth fixing.

Older practice was to vent crawl spaces. In humid climates like North Carolina, open vents often let in more moisture than they remove. Sealed, conditioned crawl spaces generally control moisture better.

It helps with ground vapor, but not with liquid water or humid air through vents. We check what your space needs.

We serve Raleigh, Cary, Apex, Garner, Wake Forest, Knightdale, Zebulon, Clayton, Holly Springs, Fuquay-Varina and the Charlotte area. Send your address with your request.

Mold needs to be removed first, then the moisture fixed so it does not return. We can do both.

Yes, we offer flexible financing options for qualifying homeowners. Ask when you request your free estimate. Terms depend on the lender and your approval.

Get a Free Crawl Space Moisture Control Estimate

Request an estimate or call (704) 727-4344.

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