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How Much Mold In A Crawl Space Is Acceptable?

How Much Mold In A Crawl Space Is Acceptable
How Much Mold In A Crawl Space Is Acceptable

Wondering how much mold in a crawl space is acceptable? We’ll cut right to the chase. The answer is none. After reading this article, you’ll find out why we say this.

Unfortunately, mold in a crawl space is pretty much a fact of life. Many homeowners never look inside their crawl space and don’t realize what’s going on in there. Their home starts to smell musty, and they wonder where the foul odor is coming from.

Crawl spaces get moldy because they’re humid, and mold can rot wood and, over time, cause structural damage. Mold can also make you sick, and most people don’t know that a certain amount of crawl space air makes its way into your home’s living area. That means you’re breathing it in. Not a pleasant thought.

In this article, we’re going to discuss signs you have mold in your crawl space, causes of a moldy crawl space, mold removal, how to prevent mold in a crawl space, and more.

How much mold in a crawl space is acceptable?

There is no acceptable level of mold in a crawl space. Mold doesn’t belong in a crawl space, period. Even a small amount of mold in a crawl space will grow and spread, and since – as we noted above – some of the air in the crawl space enters your home, you need to aim for zero mold in the crawl space. Mold is an allergen and can cause health problems.

Why you need to remove mold in your home’s crawl space

Mold in your home’s crawl space causes:

  • Unpleasant odors – Mold spores are invisible but smell bad.
  • Health problems – You don’t want to breathe mold.Mold can cause allergies and respiratory problems.
  • Damage to wood, carpets, and other items – If mold from your crawl space gets in your home’s living area, it could cause damage to wood, carpets, fabrics, drywall, etc.
  • Mold lowers your home’s property value – Who wants to buy an unhealthy house full of mold?

Signs you might have mold in a crawl space

Signs you might have mold in your crawl space include:

  • Your home smells musty – That unpleasant odor might be coming from a moldy crawl space. 
  • People living in your home have allergies, and respiratory issues – This could be from mold and other allergens floating up from the crawl space.
  • There’s visible mold on your floor and baseboards 
  • Your wooden floor is warped 
  • There’s visible mold on crawl space beams, joists, etc
  • Wooden structures in the crawl space are starting to rot – Wood rot can eventually cause structural damage.

Causes of mold in a crawl space

Mold in a crawl space is caused by moisture (i.e., high humidity). But, where does the moisture come from? Crawl space moisture comes from:

  • Concrete shrinkage cracks are hairlines (usually vertical) in a poured concrete foundation wall. While they aren’t going to affect your home’s structural integrity, they can allow moisture to enter the crawl space.
  • Soil – Soil contains moisture, and if the soil in a crawl space isn’t covered, mold could eventually start to grow.
  • Vents – Open vents allow humid air to enter the crawl space.
  • Leaky pipes – If your pipes leak water into the crawl space, mold will start to form.
  • Flooding – A recent flood will increase the level of moisture in the crawl space and, as a result, the level of mold as well.
  • Excess moisture in the soil around the foundation – If there’s a lot of water in the soil around a foundation, it will eventually find a way to get inside a crawl space. The solution is to get groundwater under control. We’ll talk more about this in a bit.

Types of mold

There are various types of mold in crawl space: black, yellow, white, and green. There’s no reason to go into detail about each one because they’re all bad. You don’t want any mold in your crawl space. If you see even a tiny amount of mold, you need to get rid of it pronto.

Crawl space mold removal

Mold in a crawl space is a big mess, and removing it takes time. It’s not a fun job. It could also expose you to allergens if you’re not extremely careful. Therefore, we recommend leaving this job to the pros. If the mold isn’t completely removed from the crawl space, it could grow again.

If you’re determined to DIY, make sure you’re wearing personal protection that’s OSHA-rated. This includes a respirator, goggles, clothing that you can later throw away (you don’t want to bring the mold into your home’s living area), gloves, etc.

Keep in mind that simply removing the mold in a crawl space doesn’t address what caused the mold to grow to begin with. If you want to keep your crawl space mold-free, you’ll need to eliminate the root cause. This might include repairing a concrete shrinkage crack, fixing leaky plumbing, or installing a drain tile system.



How to prevent mold in a crawl space

One way to prevent mold in a crawl space is to ensure there isn’t any excess water in the soil around your home’s foundation. Here are a few ways to do that:

  • Install a drain tile system – A drain tile system is a gold standard when it comes to controlling groundwater around your foundation. For more information, see How Does A Drain Tile System Work?
  • Clean your gutters regularly – Clogged gutters will cause water to spill over the side of your house and into the soil next to the foundation. From there, it could get into your crawl space and cause trouble.
  • Install downspout extensions, if necessary – Downspouts that are too short release water next to the foundation. Extensions are inexpensive, easy to install, and will carry water away from the foundation before releasing it.
  • Regrade yard, if necessary – Your yard should slope away from the foundation. If it doesn’t, water will pool near the foundation and make its way into the crawl space. A landscaper can help you with yard regrading.
  • Encapsulate the crawl spaceCrawl space encapsulation involves covering the crawl space walls and floor to prevent moisture from getting into the crawl space through the soil or the foundation walls. Adding a dehumidifier will kick this up a notch.
  • Watch for foundation cracks – These could allow water to get into the crawl space, especially if there’s excess water in the soil around the foundation with a build-up of hydrostatic pressure.

In a crawl space, no amount of mold is acceptable because even a tiny amount will grow and spread. Therefore, the only solution is to eliminate all mold in a crawl space.

If you’re struggling with mold in your home’s crawl space and you’re in our service area in Nebraska, Iowa, Kansas, and Missouri, contact us today for a repair estimate. 


Dave Epp

Dave is the President at Epp Foundation Repair with over 27 years of experience in the industry. Dave has worked on thousands of foundation, basement, concrete, and crawl space repair projects since 1993. Dave is involved in several civic and church organizations and enjoys coaching youth sports, mainly football, golfing, and elk hunting.



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