Mulch and Termites: Understanding Their Impact on House Foundations

Homeowners are often concerned about termites (Isoptera). Mulch applied to the foundation of a home is a common concern. This is a concern that raises a number of questions. Unfortunately, not all experts are in agreement on all the answers. If you are uncertain about how to mulch around your foundation, here is a short answer:

For safety, keep a 1-foot wide strip of mulch free along the foundation. Also make sure that the door and window frames are not in contact with the mulch. Keep the ground as dry as possible.
Apply mulch outside of this zone (people often use it to suppress weeds around their foundation plantings) but keep its depth at a maximum of a few inches and be sure to inspect the mulch for termites.
Let’s now explore the issue in more depth.

Drainage (Moisture), Termites and Your Foundation
There are different opinions on how much caution should be exercised when mulching near a home. Mulch is not a great source of nutrition for the termites. Mulch is not a preferred food source for termites. Mulch is a preferred food source for termites because it provides the conditions they prefer. It retains moisture which they love, and insulates from extreme temperatures. It is extremely rare that termites are present in mulch bags purchased from large box stores or commercial companies. This is because termites do not survive the process of wood shredding. Termites do not live in soil. They are instead found searching for food. Mulch is simply a way to help them flourish.

In your area, termites are a known problem.
You have experienced termite infestations yourself in the past.
Mulching near the foundation of your home is a good idea because termites can cause serious damage.

It is important to have good drainage around the foundation in any case, but is especially important when it comes to termite control. Termites love moisture. It is easy to ensure adequate drainage: grade the ground with a slope of about 5 percent away from your house in order to divert water away from your foundation. Install splash blocks and downspouts to divert water from the foundation. Make sure your gutters are cleaned.

Draw Termites Around Foundations and Mulch
Consider the subquestions that are implied in the question whether mulching around the foundations will cause termite issues.

Can the mulch come in contact with the foundation or not?
How close can the mulch come to the wooden surface of a house wall?
What types of mulch are best for termite prevention? Do wood mulches attract these pests into a yard in search of food?
Each of these questions about termite control deserves a unique answer.

Some experts advise against it (you should not allow such contact if a termiticide was applied to the soil along your foundation when your house was built). Some experts recommend against it (you should definitely not allow this contact if you applied a termiticide to the soil near the foundation of your home when building). This is the best way to eliminate termites from your home.

If you’re less paranoid, and plan to allow mulch to come in contact with your cement foundation, limit the thickness of the mulch layer to two inches. (In fact, even when kept farther away from the home, the mulch layer should not be deeper than four inches. Burnett’s Landscaping, a landscaping company in Salem Connecticut, U.S., recommends that you leave at least 8 inches between the top edge of your planting bed and wood sill plates on the wall of your home.

There is a common misconception about the type of mulch that is best to use to control termites. People assume that because termites consume wood, only wood-based mulches are problematic. This is a myth. It is also a separate question as to whether mulch, in a technical sense, actually attracts termites.

It is not that termites are attracted to a home by the wood mulch they can eat. Rather, termites already in the soil use the mulch to hide and launch an invasion of your home. All mulches, to some extent, provide moisture for termites. The best mulches are those that retain moisture well. This is a quality that your plants will enjoy, as well as termites. Even mulches which retain less water (such as stones mulches), provide pests with places to hide.

The issue isn’t so much whether mulch attracts termites (they probably were already there), but rather that mulch provides a more comfortable environment for these pests. By placing mulch around the foundation of your home, you are inviting termites to emerge from the soil to search for ways into the walls. Termites love cypress sapwood, slash and loblolly pine.

There are some types of wood mulch that termites actually dislike.

Cedar mulch
Mulch made from cypress heartwood
Southern tidewater red cypress
California redwood
Termites do not eat wood, but cellulose. The cell walls of plants (not only trees) that you grow in your backyard contain cellulose. Termites can also damage your landscaping plants.

Be Alert and Know What to Watch for
You can save a lot of cash by being on the lookout and acting quickly when you notice their presence. Find out what termites look like and what they are. Although they may look similar to “white ants,” termites are not the same size as some ants.

There are many species of termites. They are social insects that are divided into castes within their colonies. Not all termites are the same. Termites are found on every continent, except Antarctica. But parts of the U.S.’s northern tier (Northern Maine for example) have a lucky situation: The termite population is small or nonexistent.

Inspect the mulch around foundation plantings regularly to check for termites. Contact a professional termite control company immediately if you see any.