Introduction
What’s lurking beneath your floorboards could be making you sick—and slowly eating your house from the ground up.
Crawl space mold is the kind of silent menace most homeowners ignore—until the musty smell rises or the floorboards start to warp.
But this hidden intruder is more than an eyesore; it’s a trigger for allergies, a threat to your home’s structure, and a red flag for potential buyers.
So how do you get rid of mold in a crawl space under your house? The answer starts with moisture control and ends with long-term prevention. In this blog, we’ll break down everything from DIY mold-busting methods to professional-grade solutions—plus what it takes to keep it from coming back.
Why Mold in a Crawl Space is a Serious Problem
Your lungs and your foundation both have skin in the game.
Mold spores in the air can lead to a laundry list of health problems—think sneezing, coughing, asthma flare-ups, and even chronic respiratory issues.
And because air from your crawl space can circulate into your living areas, mold doesn’t stay in the basement.
Structurally, mold weakens wood and insulation, inviting rot and decay that can compromise your home’s integrity over time. Translation? Small spots can lead to big-dollar repairs.
And if you’re thinking of selling your home, mold in the crawl space is a deal-killer. It signals neglect, invites inspections, and slashes property value.
When is it more than cosmetic? If the affected area is larger than 10 square feet, smells earthy or foul, or keeps reappearing despite cleaning—it’s time to act.
Step-by-Step Guide to Mold Removal
1. Stop the Moisture First
Mold doesn’t just appear—it thrives where moisture lingers.
Before you touch the mold, you have to fix what’s feeding it. Mold spores need damp, humid conditions to grow, so cutting off that water source is step one.
Here’s what to do:
- Fix all leaks — plumbing, foundation cracks, or condensation issues.
- Install a vapor barrier — this plastic sheeting seals off the ground, keeping soil moisture from rising.
- Run a dehumidifier — your crawl space should stay below 60% humidity at all times to prevent regrowth.
Humidity isn’t just a side effect—it’s the root of the problem. Nail that, and you’re halfway to mold-free.
Prep Like a Pro (and Protect Yourself)
Mold spores don’t care who you are—they’ll go for your lungs, eyes, and skin.
That’s why preparation and protection are non-negotiable. Treat your crawl space like a hazard zone.
Your PPE checklist:
- N-95 mask or a respirator
- Non-porous gloves
- Safety goggles
- Long sleeves and pants
Ventilation tips: Open access vents if possible. Use box fans or air movers to keep fresh air flowing in—and spores blowing out.
Tools of the trade:
- HEPA-filtered vacuum — removes loose spores from surfaces and air
- Stiff-bristle brushes — ideal for scrubbing mold off wood and concrete
- Spray bottles and buckets — for applying and rinsing your cleaning agents
3. Choose Your Attack Plan: DIY vs. Pro
A. DIY Methods (for areas under 10 square feet)
If it’s a small patch, and you’re confident in your cleanup game, here are your weapons of choice:
- Vinegar: Spray undiluted or mix 1:1 with water. Let it sit 10+ minutes before scrubbing. Effective for many common mold strains.
- Baking Soda: Sprinkle directly or mix with water to create a paste. Helps deodorize and scrub.
- Borax: Mix one cup with a gallon of water. No need to rinse, but handle carefully—avoid skin and eye contact.
- Hydrogen Peroxide (3%): Spray on, wait 10–15 minutes, scrub, then dry the area thoroughly.
Warnings:
- Never mix vinegar with hydrogen peroxide—it creates a toxic gas.
- DIY is for limited cases only. If you’re unsure or overwhelmed, stop here and call a pro.
B. When to Call the Pros (for over 10 square feet)
Once the mold goes beyond what a spray bottle and elbow grease can handle, you’re in professional territory. Here’s what they bring:
- Soda Blasting: Like sandblasting but with baking soda—non-toxic and perfect for wooden joists and beams.
- Antimicrobial Treatments: These advanced sprays kill spores and prevent regrowth long after cleanup.
Pros of hiring a specialist:
- Complete mold eradication
- Structural assessments
- Guaranteed prevention strategies
- Less health risk to you and your family
Cons:
- Can cost significantly more
- Requires scheduling and potential home access
Bottom line: If it’s big, persistent, or smells like trouble—trust the experts.
VI. Summary Table: DIY vs. Professional
| Factor | DIY (Small Area <10 sq ft) | Professional (Large Area >10 sq ft) |
| Cleaning Agents | Vinegar, Baking Soda, Borax, Hydrogen Peroxide | Soda Blasting, Antimicrobial Sprays |
| Tools Needed | Brushes, Spray Bottles, PPE (mask, gloves, goggles) | HEPA Vacuums, Encapsulation Systems, Advanced PPE |
| Safety Level | Moderate – must use PPE, limited exposure | High – full containment and protective protocols |
| Effectiveness | Good for light, localized mold | Best for widespread, deep-rooted infestations |
| Cost | Low | Higher upfront, but thorough and long-lasting |
| Best Use Case | Minor surface mold, early detection | Structural mold, recurring issues, or health concerns |
Final Thoughts
Crawl space mold is sneaky—but beatable. With the right knowledge and tools, you can take control before it takes over.
Whether you’re tackling a small patch solo or calling in the pros, the key is to act fast and act smart. Mold doesn’t wait. And neither should you.
This isn’t just about your crawl space—it’s about protecting your home, your air quality, and your peace of mind.
1. What kills mold in the crawl space?
Mold in crawl spaces can be killed using vinegar, baking soda, borax, or hydrogen peroxide for small areas. For severe infestations, professionals use soda blasting and antimicrobial treatments.
2. How do you kill mold under flooring?
To kill mold under flooring, remove the affected material if possible. Clean subflooring with mold-killing agents like borax or hydrogen peroxide, then dry thoroughly and treat with a mold sealant.
3. What kills 100% of mold?
No method guarantees 100% mold eradication, but professional-grade antimicrobial treatments combined with moisture control can effectively eliminate mold and prevent recurrence.
4. How long does it take to remove mold from a crawl space?
DIY mold removal may take a day or two for small areas. Professional remediation of larger infestations can take several days, depending on the extent of damage and drying time.
5. When should I call a professional for crawl space mold?
If the mold covers more than 10 square feet, has p
Pingback: How to Test for Mold in Your Home -