When was the last time you looked at your crawl space? Have you ever? Too often, crawl spaces become havens for mold and bugs, which damage your house and impede on your standard of living. When such infestations take hold, it’s important to treat them. More importantly, you need to address their source: moisture. Remove moisture, and you can prevent bugs and mold from taking control of your crawl space and invading the rest of your house.

Signs of a Moist Crawl Space

Signs that you have too much moisture in your crawl space are fairly obvious. Fuzzies (i.e. mold growth) on the wood or across the ground under your house are one such sign. Other signs include bugs that make their way into the rest of your house — spiders, camel crickets, termites, slugs, centipedes, and millipedes all thrive where there’s moisture. Rats and damp smells are also signs of too much moisture under your house, as are pools of standing water or water that beads on surfaces.

How Mold Spreads

Mold can grow on virtually any organic structure as long as there’s enough moisture (about 70 percent relative humidity) and oxygen. Wood, paper, insulation, carpet, and dirt are all surfaces mold will grow on. As mold matures, it produces spores, which are the mold’s version of seeds. If the spores land in moist environments conducive to growth, the mold will spread. If left unchecked, it will eventually cause structural damage.

What to Do About Moisture

To address moisture in your crawl space, you have to do more than install dehumidifiers. You have to address the source of the moisture.

Standing Water

Standing water is one source. Leaky and broken pipes, runoff, floods, and cracks in the foundation are all ways large amounts of water can enter your crawl space and pool up. As the water evaporates, it increases the humidity of the air. At the same time, the relative humidity also creases, which then keeps the remaining water from evaporating.

Standing water is a problem not just because it increases the humidity, which makes the environment attractive to mold, but it attracts pests. Think of the standing water as a pool in the Sahara. It will attract all sorts of lifeforms in the area: insects, arachnids, rodents (which eat the bugs), snakes (which eat the rodents), etc. In the summer, standing water can also provide breeding space for mosquitos.

To get rid of standing water, you will have to make repairs and deal with the incoming water. This means you might have to install a French drain or a sump pump. If your plumbing is leaking, you will have to call a qualified plumber to repair it. Also, you will have to pump out or soak up the pooled water.


Another major source of moisture in crawl spaces is from the ground. When the earth in your crawl space isn’t covered up, water is able to evaporate from it. The water vapor then gets trapped under your house, increasing the humidity down there. Moisture can also seep in or evaporate through cement blocks and concrete, as well.

You can address water vapor that enters your crawl space through evaporation by encapsulation the space. Once that is done, you can decrease the remaining humidity with a dehumidifier and fans.

Outside Ventilation

The third major source of humidity in your crawl space is outside ventilation. The ventilation, of course, doesn’t itself cause the humidity; the transfer of air does. In the summer, warm air enters under the house and cools it down. Because cool air cannot hold as much moisture as warm air (think of a sponge being squeezed), the relative humidity increases. And this, in turn, decreases evaporation.

This issue is also solved through encapsulating the crawl space and then using dehumidifiers to lower the humidity.

Poor Interior Ventilation

The fourth source of moisture in your crawl space is improper ventilation from inside your house. Air from your HVAC system or from your clothes dryer should never be directed into your crawl space. Likewise, air should never be sucked from your crawl space into your house. If your crawl space isn’t encapsulated, the HVAC system is likely sucking mold spores and unwanted odors into your house if it does this. It also provides vermin and bugs an easy way into your living space. If your crawl space is encapsulated, sucking air from the space will force the HVAC fan to work extra hard.

To fix problems with your ventilation, contact a licensed HVAC specialist in your area.

Who to Contact to Find?

Depending on the source of moisture, you will have to call a different expert to handle the issue. If you have plumbing issues, you will have to call a certified plumber. HVAC issues will require an HVAC specialist. For all other needs, you can find a general contractor or one of many companies that specialize in crawl space encapsulation. If you have a large mold problem, you’ll have to call a remediation specialist.

A number of pest control companies also provide crawl space services. If you live in Columbus or Bloomington Indiana, Yes Pest Pros can provide for all your crawl-space-related needs. Yes Pest Pros treats mold, dries out crawl spaces, installs proper insulation, and encapsulates crawl spaces. They also install sump pumps and French drains.