Mold Remediation Blog

Preventing Mold Growth In Your Home’s Crawl Space

And What To Do If It’s There Already

Visiting the crawl space of your home is no one’s idea of a good time, but it’s something you should do at least twice a year. After all, it’s in your crawl space that you’ll find the first signs of trouble for most of your home’s systems. Whether it is popped venting, leaky pipes, or structural issues, symptoms tend to run downhill, and there’s nothing lower than your crawl space.

Your crawl space is also prone to building up moisture, and moisture almost always leads to mold growth, especially when combined with darkness. So while it’s good to check for mold whenever you inspect your crawl space, there are steps you can take to make sure your crawlspace stays too dry for mold to find a home.

Understanding Mold

The first thing to understand about mold is that it is everywhere, always. Every breath you take has mold spores in it. Mold only becomes an issue when it becomes concentrated in the air, which only happens around mold colonies.

What Happens When Mold Concentrates In The Air

When mold spores become too numerous in the air you breathe, you can suffer many diverse symptoms, such as:

  • Headaches
  • Fatigue
  • Allergy-like Symptoms
  • Shortness Of Breath

In more severecases, a person can have a true allergic reaction, and those with lung deficiencies can have severe reactions to heavy concentrations of mold.

What Brings Mold Into A Home

Mold needs three things to thrive: A lack of light, a good moisture source, and something to eat. That last part is why mold is so dangerous to your home. When there is mold on a wall or a joist, it isn’t just growing; it’s eating your home. If left for too long, mold will destroy the structural integrity of any home and make it unsafe for habitation.

Making Your Home Inhospitable To Mold

You can’t just leave your home open to the elements, which means that you’re going to have dark areas in your home. So, the only thing you can do is make sure that your home is too dry to support a mold colony.

But moisture isn’t inherently bad. In fact, your home needs a certain level of humidity to keep everything together. If the air is too dry, wood can get brittle and weak. The acceptable humidity range for your home is 30 – 50%. That allows enough moisture to keep your wood framing healthy but not enough to invite mold over for dinner. Achieving that balance in the lower areas of your home is the trick.

Keeping Your Crawl Space Dry

Your crawl space is in direct contact with the earth, so it requires a little care and planning to keep it too dry for mold to grow. The two main ingredients for a properly dry crawl space are insulation and ventilation.


The underside of your subfloor should be well insulated and with the insulation tight against the subfloor. This keeps heat from propagating through the floor and into your crawl space. Otherwise, the warm ceiling in a crawl space will allow condensation to form in the area, which will lead to mold in no time.


Have you ever noticed that a glass set on a towel to dry will always have droplets of water inside? And that, if you set the glass partly off the towel, it will dry completely? That’s a lot like the way your crawl space works.

With limited ventilation, it is easy to build excessive moisture in your crawl space. But if you allow good airflow through the space, the humidity levels will drop significantly. However, you need to take care to balance that airflow with the need to keep critters out from under your home.

Some argue that tightly sealing your crawl space is the best answer, but that’s only so long as there’s never a leak in your plumbing. Any moisture that gets into a sealed crawl space is going to remain there instead of evaporating away. And, as we said, mold spores are everywhere, always. Just add water.

What If You Find Mold?

If you’ve taken our advice and inspected your crawl space, what do you do if you find mold? The first thing is to find the source of the moisture that mold needs to grow. It could be a leaky pipe or condensation from an uninsulated portion of your subfloor. It could even be your gutter system’s downspouts failing to send the water away from your foundation.

Once you’ve discovered and eliminated the moisture source, verify that you have sufficient ventilation for your crawl space. You can do this by using a humidity sensor and watching the humidity levels drop after you’ve done your repairs. If the humidity levels don’t drop below 50%, then you most likely need to increase the ventilation.

The tricky part of the process will be determining what needs to be removed, repaired, or cleaned. Your best answer for this is to call in a mold professional.

Mold Remediation Services

If you have no interest in messing around in your crawl space or want to be certain that the problem will be handled professionally, call a Mold Remediation Service. They have the equipment and the knowledge necessary for full remediation of your crawl space’s mold problem.

If you call Valor Mold Removal, we will be able to tell you within a few minutes of setting up our equipment exactly how much mold is in the air down there. Other mold services will need to send samples to a lab, which will give you results in a few weeks.

Once we determine that you have a problem, we’ll find the source and take the appropriate actions. Sometimes that means hauling in equipment, and sometimes it means simply airing out the space. We always seek the simplest, most cost-effective answer for our customers.

If you are concerned that you might have a mold problem in your DC area home, contact us at Valor Mold Removal. With our specialized equipment (one of 70 in the world), we can test your entire home in a few hours and give you a room-by-room report as we go.

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96% Success Rate

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