Mold in the crawl space: what to do about it

What crawl space mold looks like

White, green or black fuzz on the joists, beams or subfloor. It starts at the coldest, dampest corner and spreads. A musty smell that is strongest near the floor registers, or in the lower part of the house, often comes from below. Growth on the wood means humidity has been above 60 percent for a long time.

What to do first

• Find the moisture. Standing water after rain, a leak, open vents in summer, wet insulation. Mold needs moisture and about 48 hours, so any water event is a reason to look.
• Do not cover it. Laying new plastic or a liner over a crawl space with mold seals the problem in.
• Do not stir it up. Scraping or pulling out moldy insulation without containment can spread spores into the house.
• Get it looked at. A technician can show you the growth, measure the moisture and explain the cause.

What proper remediation involves

Remediation done properly has four parts. Containment: the work area is sealed and put under negative air so spores do not travel into the living space. Removal: mold-damaged porous material, such as insulation, comes out and is bagged. Treatment: remaining surfaces are HEPA-vacuumed, cleaned and treated with an antimicrobial, and heavily affected wood is encapsulated or replaced. Moisture: the leak, the humidity or the drainage problem that started it is corrected, usually in the same job.

Watertight is an IICRC-certified company for remediation, and our crews work in respirators and protective gear. See mold remediation for how we handle it.

Keeping it from coming back

Treating mold without fixing the water is a temporary fix. That is why the drainage, the liner or the dehumidifier goes into the same job. For most Louisville crawl spaces that means drainage and a sump if water collects, then a sealed crawl space with a dehumidifier holding the humidity under about 60 percent.

Testing

We inspect, identify visible growth and measure moisture. For lab testing, especially for a real estate transaction, we recommend an independent tester so the results are unbiased. We do not do asbestos work; if a house needs it, we will tell you and point you to a licensed abatement contractor.