Do Termites Eat Treated Wood?

Termites cause major damage to homes and structures by eating through wood. This has led many homeowners to use treated lumber when building or renovating, hoping to prevent termite infestation. But does treated wood stop termites in their tracks? Or are these voracious insects still able to feast on woods that have been chemically altered?

Understanding the interaction between termites and treated lumber is crucial for homeowners wanting to protect their property. This article will provide a deep dive into termite behavior, the treatment process for wood, and the latest scientific research on how effectively it deters termite invasion. After reading, you’ll know to make informed decisions about treated wood and termite control for your home.

Do Termites Eat Treated Wood

What is Treated Wood?

Before understanding if termites eat treated wood, it’s important to know what treated lumber is and how it differs from regular wood. Treated wood has been injected or impregnated with chemical preservatives that help protect it from insects, fungus, rot, and other forms of decay.

The most common preservative used is chromated copper arsenate, or CCA. This mixture of chemicals contains chromium, copper, and arsenic, which are toxic to termites and other pests. The wood is placed in a pressurized chamber where the preservatives are forced deep into the fibers and cells of the wood.

Other preservatives include alkaline copper quaternary (ACQ), copper azole, borates, and creosote. Each chemical solution protects the wood through different mechanisms, like repelling and killing insects, preventing fungal growth, or making the wood indigestible.

Treated lumber is common for outdoor constructions like decks, fences, landscape timber, and picnic tables. The chemical preservation protects the wood from rot and decay far longer than untreated wood. It’s also become very popular for indoor applications like basement framing, sill plates, and interior supports.

Homeowners choose treated lumber to prevent termite infestations, fungus growth, and moisture damage. But how well does treated wood hold up against the mighty termite?

The Myth of Termite-Proof Treated Wood

The common misconception is that treated lumber is 100% resistant or ‘termite proof’. Many assume that the toxic chemicals make treated wood impossible for termites to eat through. However, scientists have found that termites can and will still infest treated wood under certain conditions.

Research shows that termites can ingest treated lumber and slowly eat through the chemical barriers intended to deter them. A study published in the Philippine Agricultural Scientist found that termites could consume approximately 25-30% of wood treated with CCA before dying from the chemicals.

Termites also can avoid directly ingesting treated wood by tunneling through the center of beams or eating around the chemical layer near the surface. One study found termites caused substantial damage by digging through the interior of CCA treated wood samples while avoiding the treated outer layers.

The level of termite resistance depends on factors like the specific chemicals used, the treatment method, penetration depth, concentration levels, and application quality. Improper treatment can lead to chemical concentrations that are too low to deter termites fully. Environmental factors also impact the longevity of the preservatives over time.

While treated wood does have termite-resistant properties, it cannot be considered ‘termite proof.’ Given the right circumstances, termites may still be able to infest and cause major structural damage.

How Termites Interact with Treated Wood

Termites have specialized digestive systems that allow them to derive nutrients from cellulose, the main component of wood. The preservatives in treated lumber are toxic and aimed to disrupt their digestion. However, some termite species have adapted to tolerate low levels of certain chemical treatments.

Several factors come into play in how effectively treated lumber deters termites:

Type of preservative chemical – Each solution has varying levels of toxicity. Borates are considered more termite-resistant than copper-based preservatives. Creosote is highly repellent. The level of protection also depends on how well the chemicals permeate the wood tissue.

Concentration and retention – Higher concentrations and deeper penetration of preservatives increase termite resistance. Standards require a certain chemical retention in treated wood, but application can vary.

Termite species – Not all termites are affected equally. Formosan termites may be more tolerant than Eastern subterranean termites of certain chemicals like CCA.

Weathering – Environmental exposure can degrade wood preservatives over time, lowering termite resistance. Moisture and temperature extremes accelerate this process.

Wood properties – Higher density wood generally accepts more preservative penetration for improved protection. Softwoods like pine are more easily treated than hardwoods.

With lower chemical concentrations or weathering, termites can overcome the treated wood’s defenses better. Even woods treated properly to standards can become vulnerable over time.

Signs of Termite Infestation in Treated Wood

Part of protecting your home is monitoring closely for any signs of termite activity. Even in treated lumber, termites may find a way. Here are indications that termites have breached your chemical defenses:

Mud tubes – Termites build narrow mud tubes along wood surfaces to create protected passageways. Tubes leading up from the soil are a major red flag.

Hollowed out galleries – Termites eat out the inside of wood, leaving a thin outer shell. Tapping wood to check for hollow areas can find hidden infestations.

Damaged paint or drywall – Termites sometimes chew through materials to reach the treated wood behind it. Bubbled or cracked surfaces may indicate activity.

Swarming winged termites – Large numbers of winged reproductive termites emerging inside is a sure sign of an active infestation in the home.

Piles of frass – Sawdust-like debris from their wood eating can build up below infested areas. A clue to look for.

Sagging floors – Eaten away structural wood can start to sag under weight. It’s a serious sign of advanced damage.

Noticing these signs early and inspecting vulnerable areas like basements and porches periodically can help detect termite invaders before they ruin your treated wood. Call a professional exterminator immediately if you confirm termites have become a foothold.

Types of Wood and Their Termite Resistance

While treated lumber can deter termites, certain wood species also have natural resistances. Understanding the termites’ preferences can guide decisions when selecting wood for home projects.

Cedar – Highly resistant to termites. The natural oils in cedar repel and are toxic to insects. Decay resistant too. Western red cedar is the ideal choice.

Pine – Very susceptible to termites. The soft wood is easily excavated. Pressure treated pine gains more resistance but less than naturally termite-resistant woods.

Plywood – The glues used in manufacturing plywood make it unpalatable for termites. They will damage surface veneers but usually not eat glue layers.

Redwood – Another naturally durable wood. Redwood contains chemicals like tannins that deter termites. But not considered as resistant as cedar.

Cypress – While not the toughest wood, cypress does have moderate natural durability against termites and decay. Southern yellow cypress is a decent option.

Composite lumber – Plastic, metal, and cement mixed into composites create a termite barrier. Brands like Trex are inedible to insects.

Opting for wood species that termites avoid can be an alternative or addition to treated lumber for protecting against infestation. Consulting an expert can help select the ideal wood for your home project and location.

Alternative Solutions and Preventive Measures

While treated wood has preservatives to deter termites, there are also additional steps a homeowner can take to protect their property:

  • Use naturally termite-resistant woods like cedar, cypress, or redwood for vulnerable structural components.
  • Have a professional treat soil around the home’s foundation with termiticides to create a chemical barrier.
  • Ensure outdoor sprinklers don’t excessively moisten soil, attracting termites.
  • Seal any cracks in foundation walls or openings around utilities to prevent termites from entering.
  • Install a mesh termite barrier around foundation walls to block underground entry.
  • Have wood structures properly treated by a professional at the time of construction or renovation.
  • Conduct regular inspections for signs of termites, especially in damp areas. Call an exterminator immediately if found.
  • Have an annual termite inspection and treatment done by a pest control company. Maintain protection over time.

Taking a layered approach provides the best defense against devastating termite damage. Treated lumber can provide powerful protection, especially when combined with other preventive measures

Understanding Termite Behavior

To fully grasp the interaction between termites and treated wood, it’s important to understand what drives termite behavior and preferences. There are a few key factors that attract termites to specific wood sources:

Cellulose – Termites can only digest cellulose, requiring a food source high in this wood component. Softwoods have more cellulose.

Moisture – Termites need a constantly moist environment to survive. Damp wood in wet soil is ideal habitat.

Toxins – Termites avoid woods with high levels of natural toxins like tannins, resins, and oils. Treated woods use this principle.

Hardness – Dense hardwoods are more difficult for termites to excavate and consume. Softwoods are easier targets.

Decay – Fungi breaking down wood plant fibers produces nutrients termites can absorb. Decayed wood attracts them.

These factors drive termites to seek out wood sources that balance cellulose content and moisture levels while avoiding toxicity. Understanding these motivations provides clues to protect wood structures from infestation.

Different Chemical Treatments for Wood

Not all termite-resistant wood treatments are created equal. The level of protection depends greatly on the type of chemical preservative used. Here are some of the most common options:

Chromated Copper Arsenate (CCA) – The historically most used preservative for residential lumber. Provides decent protection but concerns over arsenic leakage have reduced use. Banned for some residential uses.

Alkaline Copper Quaternary (ACQ) – Water-based treatment without arsenic. Uses copper as active ingredient. Resistance depends on retention level in wood but generally protects well.

Copper Azole – Utilizes copper coupled with an organic azole compound. Considered more effective than CCA or ACQ, but also more expensive. Used for decks, landscaping, and fences.

Disodium Octaborate Tetrahydrate – Borates deter termites by disrupting their digestive system. Environmentally friendly and inexpensive. Leaches out more readily than other options.

Creosote – Derived from coal tar, it deeply penetrates and preserves wood. Toxic and repels termites. It is restricted in residential uses but common for outdoor utility poles.

Fipronil – A newer termiticide occasionally used in wood treatments. Very toxic to insects. Studies show excellent termite mortality rates. Expensive and not widely available.

Understanding the pros and cons of each solution can guide choices in treated lumber for optimal termite protection. Periodic reapplication may be needed as preservatives dissipate over time.

Environmental Factors Affecting Termite Infestation

Termites are attracted to certain environmental conditions that support their colonies. Dampness, heat, and food sources draw them in. Being aware of these factors can help monitor risks:

Moisture – The major attractant. Termites need high humidity. Standing water, downspouts, and leaky pipes around the home provide moisture.

Heat – Warmer temperatures speed up termite metabolism. South-facing walls and heat buildup in confined spaces raise vulnerability.

Wood Piles – Stacks of firewood or construction lumber give termites an unlimited food source. Avoid storing wood against structures.

Tree Roots – Roots penetrating near foundations offer hidden access. Trimming back trees and shrubs around the home is advised.

Soil Contact – Wood touching soil creates the highest risk. Steps like elevating beams off ground level can help reduce access.

Cracks – Any cracks or entry points in the foundation give termites an easy way into wood structures. Seal them up.

Closely monitoring these factors provides warnings and ways to disrupt attractive conditions around your home strategically. It limits the likelihood termites discover and feast on your wood.


While treated lumber has definite termite-resistant properties, it is still vulnerable under the right circumstances. Termites may penetrate the chemical barriers through persistence, tolerance, and avoidance behaviors. Environmental factors also play a major role.

Vigilance is key for homeowners. Inspect regularly for early signs of termite infestation. Combine treated wood with preventative measures like maintaining dryness around the home, sealing entry points, clearing wood debris, and having professional treatments done regularly.

Utilizing wood species naturally repellent to termites is also an effective strategy, either in place of or along with treated lumber. A multi-pronged approach provides layered defenses against termite invasion.

Protecting your home from termites requires diligence, but with the right knowledge of their behaviors and vulnerabilities, treated wood can be an effective part of your arsenal. While not ‘termite proof,’ treated lumber can be a powerful deterrent when used strategically as part of an integrated pest management plan.