Crawl space mold in Upstate SC homes

If you live in the Upstate and your house sits on a crawlspace, there's a good chance some of the wood under your floor has seen mold. It's one of the most common things we find in Greenville, Spartanburg and Anderson homes. Most of the time it's manageable. The key is understanding why it's there.

Why Upstate crawlspaces grow mold

• Humid summer air. Most older homes here have vented crawlspaces. In summer, the vents pull in warm, humid outdoor air. When that air meets the cooler soil, joists and subfloor, moisture condenses on the wood.
• Red clay that holds water. Our clay soil stays damp long after a rain. Without a good vapor barrier, that moisture evaporates straight into the crawlspace.
• Torn or missing vapor barriers. Plastic sheeting gets torn by service techs, pests and time. Even a few uncovered areas add a lot of moisture.
• Drainage and plumbing. Gutters that dump at the foundation, grading that slopes toward the house, and slow plumbing leaks all show up as standing water or damp soil underneath.
• HVAC in the crawlspace. Ducts and air handlers that sweat in summer, and condensate lines that drain under the house, keep the space damp.

Signs you have crawl space mold

• A musty smell in rooms over the crawlspace, often stronger when the AC first comes on
• Hardwood floors that cup or feel soft
• Insulation sagging or falling from between the joists
• Standing water, wet soil or torn plastic when you look through the access door
• Dark staining or fuzzy white, gray or green growth on joists and the underside of the subfloor

Not everything white is mold. White, crusty deposits on block foundation walls are usually efflorescence, which is minerals left behind as water moves through masonry. It's a sign of moisture, but it isn't mold.

Does crawl space mold affect the air in your home?

It can. Air moves up from the crawlspace into the living space through gaps around pipes, wiring, ducts and floor seams, especially in older homes. That's why a crawlspace problem often shows up as a musty smell upstairs. Whether it's affecting your indoor air is something testing can answer: air samples from the living space are compared with an outdoor control, and surface samples can identify what's growing on the framing.

What to do about it

1. Find and stop the moisture. Fix gutters, downspouts and grading first. Repair plumbing leaks and make sure condensate lines drain away from the house.
2. Cover the ground. A continuous vapor barrier, overlapped and sealed, cuts down the moisture coming off the soil.
3. Control the air. For many Upstate homes, sealing the vents and adding a dehumidifier or conditioned air (often called encapsulation) is the long-term fix. A licensed contractor can tell you what fits your house.
4. Deal with the existing growth. Light surface growth on structurally sound wood is often cleaned once the moisture is under control. Heavier growth or damaged wood needs a remediation company.
5. Verify. After any cleanup or encapsulation, clearance testing confirms the work did what it was supposed to.

When testing is worth it

You don't need a test to know a crawlspace is damp. Testing is worth it when you need to know whether the problem is reaching your living space, when someone in the home is having symptoms, when you're buying or selling, or when you've been quoted an expensive remediation and want an independent answer first. See why to test before you pay for mold removal.

Preston Johnson is a licensed residential contractor with the SC Residential Builders Commission, so a crawlspace inspection with us looks at the building, not just the samples: where the water is coming from and what will actually fix it.