You might not see them. You might not hear them. But there may be an entire population of pests living in your home's crawl space. Pests you may find in your crawl space range from furry mammals like chipmunks, rats and mice, to destructive insects and bugs like termites.

rat in crawl space

An insect or animal in your crawl space will often gnaw, chew or eat its way upwards, following air ducts, pipes and electrical wiring to get into your home's living spaces, walls, attic and insulation. Whether you want to know how to get rid of chipmunks in your crawl space, or you want to help prevent future pest problems like rats in the crawl space, you need to understand why pests like this space – and how they can get inside.

Pest problems in a crawl space: what is a crawl space?

When your home was being built, your general contractor likely chose one of six common foundation types:

  1. Monolithic slab
  2. Supported slab
  3. Floating slab
  4. Crawl space
  5. Plenum space
  6. Full basement

A crawl space foundation is a common in homes across North America. When a home has a crawl space, it means the house sits above a shallow space (3–4 feet high or less) enclosed by the foundation wall. While the sides are enclosed, the crawl space itself usually sits on bare soil. However, in some cases, the crawl space may be composed of gravel or concrete.

What is the purpose of a crawl space?

Setting a house atop a crawl space provides convenient access to plumbing, electrical wiring and ductwork, making home installation, repair and maintenance easier pre- and post-construction.

A crawl space also keeps your house off the ground. This provides protection from damage if your property is prone to flooding. However, homeowners should be aware that crawl spaces can provide attractive shelter for many types of pests.

Does my house have a crawl space?

You probably already know if your home has a crawl space. Some of the most common types of houses that feature crawl spaces include:

  1. Manufactured homes
  2. Prefab homes
  3. Modular homes
  4. Traditional or older homes

If your home has a crawl space, it may extend beneath the entire floor plan of your house and is likely accessible from the outside. In some cases, your crawl space may only extend below part of your house, especially if your home is built on a grade or has a partial basement.

The best and only way to measure the size of your crawl space is to get into the space itself. This is also the most effective way to ascertain the extent of a potential rat, mouse or pest problem in your crawl space. This is best done by a professional, but some homeowners are comfortable checking for themselves.

Animals in crawl space: what kinds of pests can occupy my crawl space?

Crawl spaces are dark, protected from most of the elements, and relatively warm and humid compared to the surrounding environment. That's why they're often a haven for a range of pests.

Some of the most common pest problems you'll encounter in your home's crawl space include:

  1. Rodents (mice, rats, chipmunks, etc.)
  2. Ground-dwelling insects (millipedes, termites, etc.)
  3. Carpenter ants
  4. Cockroaches
  5. Crickets
  6. Spiders
  7. Beetles
  8. Flying insects (wasps, hornets, ground-dwelling bees, etc.)

Crawl space pest prevention: how can I help prevent pests from occupying my crawl space?

Because you probably aren't in your crawl space very often, pest problems under your home can spread before you even realize there's an issue.

So, the best pest defense is a good pest offense. Take preventive measures to help stop crawl space pest problems before they even start.

Change your landscaping

Poorly planned or maintained landscaping may serve as an invitation for pests to explore your crawl space. Keep debris, bushes, brush, grass, mulch and other organic material away from the edges of your home's foundation. Many pests, including ants, centipedes, rodents and termites, are attracted to this organic matter and will use it as a home base.

Keep your landscaping tidy and trimmed to help prevent these pests from finding and moving into your crawl space.

Seal crawl space openings where pests may enter

You can't do much if your crawl space's floor is bare soil. However, you can help limit and deter pests by sealing as many potential entryways into your the space as possible.

Some pests like mice, rats and chipmunks can squeeze through gaps that are as small as half an inch.

Common crawl space openings include:

  1. Gaps between the foundation and the soil
  2. Gaps between the foundation walls and your home's floor
  3. Gaps around pipes, wiring, etc.

Though treatment by a professional is recommended, these gaps may be filled with spray foam insulation or even stuffed with steel wool. You can also use caulk, but only if the gaps are very narrow (e.g., narrow cracks in your flooring).

Do not seal ventilation openings in your foundation without consulting a professional. If vents are sealed, other measures must be taken to prevent moisture buildup in your crawl space.

Control moisture in the crawl space

Many pests in your crawl space can survive a long time without eating, but all pests need at least minimal water and moisture. For instance, rodents need water to drink, and cockroaches and termites (which originally hail from tropical climates) thrive with humid air and moist soil. The following three methods can help control moisture and keep your crawl space dry, helping to prevent many crawl space pest infestations.

1. Spread a crawl space vapor barrier

Most crawl spaces will benefit from a vapor barrier, but especially those that have a bare-soil floor. A vapor barrier is usually plastic sheeting placed on the soil that helps to prevent moisture in the soil from seeping up into your crawl space. Have a professional install a vapor barrier to ensure it's properly installed and avoid possible damage to the home.

2. Use crawl space encapsulation

Most crawl spaces aren't fully separated from living spaces, which is what a contractor might commonly refer to as your home's building envelope. This allows pests to move up from the crawl space and find their way into your home.

Crawl space encapsulation requires mitigating all mold and drainage problems (after all, if there are pre-existing problems in your crawl space, you won't want to seal them in permanently).

Encapsulation usually entails a combination of reinforced liners and dehumidifiers.

Again, installation and set-up is something that should be done by a professional.

3. Install ventilators

A dry crawl space is less prone to attracting and harboring pests. Plus, dry wood (12 percent moisture content or less) is less susceptible to infestations from termites, beetles, ants, mold and other common crawl space problems.

Adding a ventilator can help to prevent air from getting trapped in your crawl space where humidity can build up and moisture condenses. Because every home is different, the specifications for installing air vents may differ from one home to the next. In order for a ventilator to work properly, professional installation is recommended.

Contact Terminix® for an inspection today

Trained pest control professionals can inspect your crawl space and help you identify any problems. Crawl spaces are especially prone to termite issues, and at Terminix, we offer free initial termite inspections by teams of trained experts. We can also inspect and help defend your crawl space from other pests like rats, mice and ants with services like encapsulation and vapor barriers.

It's difficult to diagnose or identify a crawl space pest problem without a physical inspection. Don't let crawl space problems get out of control. Contact Terminix online to schedule your inspection today.

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