Mold in the Crawl Space Under Your Lafayette Home: Causes, Checks and Fixes

If your house sits on piers or a raised foundation, the space underneath is one of the most common places mold grows in Acadiana homes, often for months before anyone notices. The first clue is usually a musty smell after a rain, floors that feel soft, or fuzz on the joists when someone finally crawls under the house. Here's what's going on down there, what you can check yourself, and when to bring in a pro.

Why crawl spaces under Lafayette homes stay damp

Mold needs moisture. The EPA puts it simply: the key to mold control is moisture control. Crawl spaces in south Louisiana get moisture from several directions at once:

• The ground itself. Bare soil gives off water vapor all year. Without a ground cover (a plastic vapor barrier), that moisture rises into the wood framing.
• Humid outdoor air. Many older raised homes have open foundation vents. In summer, warm, humid air flows in and meets surfaces that are cooler, like the underside of an air-conditioned floor or metal ductwork. That's where condensation forms.
• Rain and drainage. Lafayette Regional Airport averages about 63 inches of precipitation a year, according to NOAA's 1991–2020 climate normals. Downspouts that dump next to the foundation, or soil that slopes toward the house, send that water underneath.
• Plumbing and AC. A slow drip from a supply line, a drain joint, or an AC condensate line can soak one area of subfloor for months without showing up inside.

Together, these keep wood damp enough for mold even when there's never standing water.

Signs of crawl space mold

• A musty smell inside, often stronger after rain or when the AC kicks on
• Floors that feel soft or bouncy, or boards that cup
• Sagging, wet, or fallen insulation between the joists
• White, gray, green or black growth on joists, beams or subfloor

Color doesn't tell you much. The CDC notes that you don't need to know the type of mold to deal with it; if you see or smell it, it should be removed and the moisture problem fixed.

What you can check yourself

If you can get into the crawl space safely (watch for wiring, sharp objects, pests and tight spots), a flashlight and a phone camera go a long way:

1. Look at the ground cover. Is there a vapor barrier at all? Is it torn, bunched up, or missing in sections?
2. Look for water. Standing water, wet soil, or water lines on the piers point to a drainage or plumbing issue.
3. Check the ductwork. Sweating ducts or dripping insulation wrap in summer point to condensation.
4. Check the wood. Photograph any growth or staining on joists and subfloor, and note where it is, especially near plumbing, under bathrooms and kitchens, and around the AC.
5. Walk the outside. Where do the downspouts discharge? Does the soil slope away from the house? The EPA recommends making sure the ground slopes away from the foundation so water doesn't collect there.

An inexpensive humidity meter left under the house for a week or two also helps. For living spaces, the EPA suggests keeping indoor relative humidity below 60 percent, ideally 30 to 50 percent. A crawl space that stays well above that is a moisture problem worth solving.

Why spraying it isn't enough

Crawl space sprays and foggers look like a quick fix. But the EPA notes that dead mold can still cause allergic reactions in some people, so it has to be removed, not just killed. And if the moisture source isn't fixed, the mold comes back.

What a proper fix usually involves

Every crawl space is different, but a lasting fix usually has two parts:

1. Remove the growth. That means cleaning or removing mold from joists, beams and subfloor, and taking out materials that can't be cleaned, like moldy fiberglass insulation. Doing this without spreading spores into the house takes care and the right equipment.

2. Control the moisture. Depending on what's causing it, that can include:

• Fixing plumbing or AC drain leaks
• Redirecting downspouts and improving drainage around the house
• Installing or replacing a ground vapor barrier
• Insulating sweating ductwork
• Sealing the crawl space and drying it with a dehumidifier, sometimes called encapsulation

Whether a vented or sealed crawl space suits your house depends on its construction, drainage and HVAC setup. That's a call for someone who has actually been under it.

When to call a pro

The EPA says homeowners can usually handle mold covering less than about 10 square feet. Crawl space mold rarely stays that small, and working in a tight, dirty space makes containment hard. It's time to call when:

• Growth covers more than a few joists or a large patch of subfloor
• There's standing water or wet soil under the house
• Floors are soft or sagging, which can mean the wood is damaged
• The smell is reaching your living space
• Mold came back after you cleaned or sprayed it

Ask any contractor how they'll find and fix the moisture source and keep spores out of the house. In Louisiana, mold remediation jobs of $7,500 or more require a mold remediation license from the Louisiana State Licensing Board for Contractors, and you can look up a contractor's license on the LSLBC website.

Get a local pro under your house

If you've found mold under your home or can't track down that musty smell, learn more about crawl space mold removal. If a leak or storm water caused it, start with water damage restoration so the structure gets dried first. Homeowners just south of the city can read about mold remediation in Broussard.

One call connects you with a local pro. Call (337) 205-7937 to describe what you're seeing and get a free, no-pressure quote.

Frequently asked questions

Will a vapor barrier alone fix crawl space mold?
Usually not. A ground vapor barrier cuts down moisture coming up from the soil, but existing growth still has to be removed. Other sources, like leaks, poor drainage or sweating ducts, also have to be fixed.

Should I close my crawl space vents?
Not on your own without a plan. Closing vents without adding a proper ground cover and a way to dry the space can trap moisture. Whether to keep a crawl space vented or seal it depends on the house, so get it assessed first.

Do I need mold testing before crawl space mold removal?
Often not. The EPA says sampling usually isn't necessary when mold is visible, and the CDC doesn't recommend routine testing. If you want testing, Louisiana licenses mold assessment separately from remediation, so hire an independent licensed assessor.

Does homeowners insurance cover crawl space mold?
It depends on your policy and what caused it. Mold from a sudden covered event, like a burst pipe, is treated differently from mold caused by long-term humidity. Check your policy or ask your agent. Your insurer decides what's covered.

Lafayette Mold Pros connects homeowners with independent local mold remediation professionals.

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