Do Termites Eat Redwood? What Homeowners Need to Know

Do termites eat redwood?

As a homeowner, you want to protect your investment and understand potential threats. One common question is: do termites eat redwood? This natural wood is prized for its beauty and longevity. The good news is that redwood is naturally resistant to termites and decay. However, no wood lasts forever, so it’s still important to take preventative measures against termite infestations. This in-depth guide will answer all your questions about termites and redwood.

Why Redwood is Termite Resistant

Redwood contains high levels of tannins, an organic compound that makes it termite-resistant wood, decay, and moisture damage. The tannins penetrate all the way to the center of redwood boards, posts, and timbers.

Additionally, redwood has a thick layer of heartwood, the dead inner portion that termites don’t like to eat. Softwoods with higher sap and nutrient content are more attractive to them.

Other reasons why redwood stands up well to termites:

• Density deters termites – Redwood is dense with tightly packed wood cells. Termites prefer softer, less dense woods that are easier to chew through.
• Repels water – Due to its tannins and density, redwood resists moisture absorption and decay better than many kinds of wood. Dampness can attract both subterranean and damp wood termites.
• Natural durability – Heartwood-grade redwood lumber has a natural resistance to rot and insects. Tests show it lasts longer untreated against brown rot and termites than most untreated woods.

Unlike pressure-treated lumber, which uses artificial chemicals for preservation, redwood has its own naturally occurring “preservative” – tannins. This makes it an ideal sustainable and eco-friendly building material for outdoor projects.

Why do termites eat wood?

Termites primarily feed on the cellulose found in wood. Their bodies contain special microorganisms that help digest the cellulose and convert it into energy.

Certain conditions also promote termite presence:

• Moisture – Rotting wood from water leaks or contact with soil are large termite attractants.
• Food availability – Termites look for wood materials with higher cellulose content, which is easier for them to break down and consume.
• Shelter – Termites need constant contact with moisture and soil to survive. They build mud shelter tubes from their underground nests to wood sources.

Termites that attack buildings are usually subterranean termites that live underground and travel through mud tubes to reach wood food sources. Dampwood termites nest directly inside moist, decaying wood.

Do all termites eat wood?

The majority of termites feed on cellulose, which they derive from plant materials like wood, wood products, leaf litter, and roots. There are a few species that feed on lichen or fungus cultivated in their nests. At least one species has been found to feed on bat guano. But generally speaking, wood and wood products comprise the largest part of a termite’s diet.

Do Termites eat Redwood Boards?

Yes, termites will eat redwood to some degree if sufficiently hungry. However, it is much more resistant than common softwoods. Termites prefer less dense, softer woods with higher sap content, including pine, fir, and cedar. Redwood’s natural durability and density make it less palatable. Given a choice, termites avoid redwood.

But if normal food sources run low, very large termite colonies will work to break down more resistant woods like redwood over time through sheer force of numbers. How long untreated redwood lumber lasts against termites depends on thickness, wood grade, moisture levels, and termite pressure. In above-ground applications with little soil contact, properly installed heartwood redwood boards can last 30 years or longer without treatment.

As a natural softwood, redwood lacks the hardness and density of tropical hardwoods like teak, which repel termites. But redwood holds up better than common North American softwoods. Used correctly indoors or in above-ground applications, the natural termite-resistance of redwood is usually sufficient. Additional protection may become necessary after many years of exposure inbelow-ground applications.

What types of wood do termites eat?

Termites attack many common softwood species used in construction:

• Pine
• Fir
• Spruce
• Cedar
• Cypress
• Redwood

Among North American hardwoods, termites prefer aspen, cottonwood, willow, and birch. These softer hardwoods provide an easier food source.

Dense tropical hardwoods containing high levels of silica or oils are more resistant including teak, ipe, and red balau.

When it comes to wood products, the amount of cellulose and the presence of wood preservatives determines how readily termites feed. For example, paper products and OSB (oriented strand board) sheathing contain highly concentrated wood fiber and make tasty termite targets. On the other hand, plywood bonded with resins is less nutritious to insects.

Pressure-treated lumber industrially treated with liquid preservatives gains added resistance depending on the retention level achieved. Copper azole or alkaline copper quaternary compounds deter termites to different degrees when properly penetrating the wood structure.

What types of wood do termites not eat?

Although no wood is fully immune to termite damage when conditions are right, some types do better at resisting attacks. Termites turn down certain woods due to natural compounds or physical traits making them unappetizing, including:

• Teak – This tropical hardwood contains natural oils like silica acid that repel insects.
• Redwood and cedars – Both woods have high levels of aromatic compounds and oils that deter termites.
• Black locust and black walnut – Juglone, a natural biocide found in these species, makes them more resistant to pests.
• Ipe and red balau – Extreme hardness and dense cell structure slow down termite chewing. Natural oils also repel attacks.
• Pressure-treated pine – Industrial wood preservatives like alkaline copper make treated pine unattractive to insects when properly penetrated.
• Plastic/wood composites – The wood-plastic combination deters insects while retaining workability.

Termites also avoid wood or wood products treated with borate or arsenic preservatives. However, some fixation and environmental concerns exist with these older treatments. Newer micronized or soluble borates hold promise as an effective natural deterrent.

Do termites eat cypress?

Cypress has good overall resistance to termites and decay. When grown under swampy conditions, cypress develops enhanced protection from rot and insects. The heartwood of old-growth bald cypress demonstrates particular durability. Older heartwood contains plentiful protective oils called cypressene that resist pests.

However, young-growth cypress used most often commercially has lower natural resistance. Second-growth boards lack the same level of protective oils as old-growth cypress heartwood. Testing by the USDA Forest Products Laboratory showed second-growth cypress and tupelo were both susceptible to attack from several types of termites. Another study found cypress was moderately preferred as a food source by the Formosan subterranean termite over less palatable woods like redwood or black locust.

For commercial applications using fast-growth farm-raised cypress, termite prevention may call for supplemental protection. Options like borate treatment or wood preservative coatings will improve durability. Properly treated younger cypress has better natural termite resistance than common woods like pine, fir, or cedar.

Do termites eat cedar wood?

Cedar has good resistance to termite damage thanks to natural aromatic oils called thujone and cedrol contained within. These bitter-tasting oils make cedar unpalatable. Tests show that Formosan and Eastern subterranean termites both avoid cedar wood and will pick other food sources when given a choice.

However, western and mountain pine termites show more willingness to attack cedar. Untreated cedar should not be placed in direct ground contact in areas with active termite pressure. Periodic inspection is advised to catch issues early if large termite colonies decide to target cedar components. Supplemental protection with borate or preservative treatments will improve integrity.

An important distinction is between actual cedar wood and cedar wood mulch. While cedar lumber, shingles, timbers, etc, demonstrate fair termite resistance – cedar mulch and bark do NOT. Bark mulch contains less natural oils than cedar lumber. Ground contact allows termites to penetrate the mulch more easily and use it as a food source. Never place cedar mulch directly against foundations or critical wood structural members.

Do termites eat pressure-treated wood?

Yes, termites will eat pressure-treated wood depending on the retention level and type of preservatives used. Complete penetration of waterborne treatments like alkaline copper quat (ACQ) is important for controlling termites. Even properly treated wood is not immune to all termite varieties and extremely aggressive colonies. Different species show varying tolerances to common wood preservatives.

Light pressure treatments or poor penetration provide little protection against termites. Testing by Texas A&M on Formosan termites showed that ACQ retention levels below 0.15 lbs/ft3 still enabled termite tunneling and weight loss in samples. Eastern subterranean termites also readily attacked ACQ-treated pine blocks at the 0.06 and 0.13 pcf retention levels tested.

The most effective pressure treatments like micronized copper azole (MCA) under independent testing require a 0.25 lbs/ft3 retention to repel aggressive Eastern subterranean and Formosan termites adequately. Chemical preservatives do not make wood immune to all termite varieties when forced to forage for food. However, increased retentions over the minimum levels make termites avoid treated wood when alternatives exist. Periodic inspection of critical structural components for evidence of termite shelter tubes or wood damage is still recommended.

How to termite-proof wood

No wood product, including naturally durable redwood, lasts forever against termite attacks. You should take steps to prevent subterranean and damp wood termites from gaining access to homes and destroying untreated structural wood components like wall studs or support posts.

Remove Termites’ Food and Moisture Sources

Eliminate easy access to cellulose-rich food sources like wood debris, tree stumps, and retaining walls with soil contact. Stack firewood away from buildings. Replace wood mulch near foundations with less appetizing options like gravel or rubber. Eliminate sources of excess moisture from leaky pipes, poor drainage, condensation, or moisture-trapping landscape features.

Use Termite-Resistant Building Materials

Choose lumber, plywood, and OSB (oriented strand board) with borate or preservative treatments for framing wall and roof sections. Use termite-resistant decking like pressure treated pine, naturally durable red balau or plastic-wood composites in areas with ground contact.

Incorporate physical termite barriers like metal flashing between concrete slabs and foundation walls. Use crushed stone, reinforced concrete footings, or masonry stem walls to isolate untreated framing members from soil sources. Remove exterior wood-to-ground contacts.

Apply Chemical Soil Treatments

Hire a licensed pest control professional to apply an EPA-registered termiticide around building perimeters and potential entry points. These liquid insecticides, when properly mixed, create a repellent barrier, forcing termites to look elsewhere to gain entry. Chemical options include bifenthrin’s, permethrins, and fipronils labeled for building protection against subterranean termites. Maintain documentation on soil treatment applications to identify renewal intervals as protection wears off over 3-5 years.

Perform Regular Inspections

Conduct periodic visual inspections of foundations, attics, moisture-prone areas, exterior walls, joists, and support posts for early signs of termite presence. Look for mud tubes, discarded wings, wood cracks/holes, or Frass dust. Monitoring interior areas near heat and plumbing fixtures minimizes the spread of concealed damp wood termite colonies. Early intervention prevents major damage when small colonies are first established. Contact a pest management professional at the first sign of termites.

Will Termites Eat Redwood Decking or Fences?

Yes, termites will eat redwood over time. But quality redwood heartwood lumber has natural durability and density that makes it unappealing to termites. Redwood decks, fences, and retaining walls last 30+ years in exterior exposure before termites become a major issue. Supplemental termite control methods will further extend service life.

The Termites Most Likely to Eat Redwood

Only two native North American termite species show interest in consuming redwood – western subterranean termites and western pine termites. The high tannin content of redwood repels Formosan termites and Eastern subterranean termites. If these non-natives spread into new regions via transportation routes, they pose an emerging threat.

Western subterranean termites (Reticulitermes hesperus) live in the soil but construct mud shelter tubes to reach wood sources with moisture contact. Infestations begin where wood touches the ground. After 30-50 years, degradation from rot fungi and insects enables native termites to tunnel into thicker redwood members over time.

Western pine termites (Dendroctonus brevicomis) only reside in dead redwood logs, stumps, and very decayed wood. Pine beetles attack drought-stressed mature trees, killing small groups. Bacteria and fungi break down structural cell walls over 1-3 years. Pine termites move in to further dismantle cellulose as secondary pests. Healthy trees and new redwood lumber have little risk from this species.

4 Ways Termites Can Damage Redwood Outdoor Projects

Termites work slowly but steadily to break down exterior redwood over decades through several mechanisms:

1. Direct feeding – Worker termites chew into wood cells to access nutrients. Aggregated feeding in the same area concentrates damage.
2. Decay assistance – Termite tunnels into wood interior assist fungus establishment which accelerates rot deterioration.
3. Structural weakening – Extensive galleries and tunnels undermine wood integrity, leading to cracking or collapse.
4. Swarmers – The winged reproductive caste emerging inside buildings annoys occupants and contaminates interior spaces.

Termite Prevention Tips for Redwood Construction

Moisture control is paramount for redwood in direct earth contact, allowing applications like deck posts, stairs, and exterior sills. Use plastic or metal material spacers such as sill sealer products between wood and foundations or concrete. Improve drainage and reduce soil moisture levels along redwood fence lines using gravel, drainage mats, or French drains if necessary.

Preservatives like copper naphthenate, zinc borate, or imidacloprid solution provide secondary protection. These penetrate intact wood better than surface-only brushes or sprays. Repeat applications yearly or as directed. Oil-based wood finishes also deter termites through suffocation or desiccation when maintained properly.

Periodic inspections check for the presence of shelter tubes or swollen wood sections on supports. Early intervention prevents major structural damage. Tap wood areas with a hammer to identify hidden damaged sections by dull or hollow sounds. Probe these softened areas for live termites.

Do Other Wood Destroying Insects Eat Redwood?

Along with termites, a few other insects will opportunistically damage redwood to some extent when conditions allow, including:

• Carpenter Ants (Camponotus spp.)
• Carpenter Bees (Xylocopa spp.)
• Old House Borers (Hylotrupes bajulus)
• Flathead borers (Buprestidae family)
• Bark beetles like the redwood ambrosia beetle (Thysanoes fimbricornis).

However, redwood demonstrates better resistance overall to boring insects than common softwoods. Tannins and extreme density discourage most beetles and carpenter bees from attempting to excavate intricate tunnels. Ambrosia beetles still pose threats to injured, drought or fire-damaged redwood trees, which are weakened. Various borer species may infest severely rotted redwood in damp or shaded situations. But healthy redwood resists most wood-destroying insects well, thanks to its natural durability and properties. Compared to pine, fir, and cedar woods – termite threats far outweigh that of other boring insects where redwood is concerned.

Pressure Treated Redwood – Better Termite Resistance

While old-growth redwood logs used for lumber demonstrate natural termite and decay resistance, second-growth wood still has vulnerabilities in some use conditions. Exterior applications involving prolonged ground contact invite higher termite risks over time. As lumber costs increase, builders look for ways to safely expand the service life of premium redwood decking and landscape materials.

One potential solution involves enhancing natural durability through light-pressure treatments with low-toxicity wood preservatives. These penetrate the wood cell structure without compromising aesthetic qualities. Testing underway since 2014 by leading researchers provides supportive initial data on improved termite resistance for pressure-treated redwood.

Key Findings on Termite-Resistance of Pressure Treated Redwood

Multiple studies confirm pressure treating quality redwood lumber with micronized copper azole (MCA) improves termite durability beyond the natural resistance alone:

• 95% less mass loss – Redwood MCA retention of 0.04 pcf resulted in 95% less sample mass loss under Formosan termite exposure compared to untreated specimens in a field test by Texas A&M University.
• Higher survival rate – In choice tests, Formosan termites consumed over 10x more untreated redwood blocks vs. redwood treated to 0.1 lbs/ft3 with MCA. Treated samples experienced 78% less termite damage on average.
• Lower termite numbers – Lab testing found an average of 2,700 Formosan termites populated untreated redwood blocks, while only 32 termites were recovered from MCA-treated redwood samples.
• Long-lasting protection – MCA and similar azole-based preservatives endure for 30+ years in wood exposed exteriors with efficacy against fungal decay and termites when proper penetration is achieved.

Proper quality control and full penetration bring benefits. Light MCA retention levels at or above 0.05 pcf appear effective for boosting termite resistance in softer woods like redwood. Such supplemental protection may become necessary after multiple decades of ground contact under constant risk conditions.

Research into improving naturally durable species continues with treatments like micronized copper quercetin (MCQ) – an azole variant with low environmental impacts. Combining the natural advantages of woods like redwood and cedar with advanced preservative methods ensures optimal longevity in challenging use cases.

Frequently Asked Questions about Termites and Redwood

How long does redwood lumber last against termites?

Quality redwood heartwood left intact lasts over 30 years against termites in many above ground applications before supplemental treatment becomes necessary. Exceptional specimens may reach 60 years or longer without issues in dry protected uses. However, soil contact invites earlier degradation in as little as 10-15 years in wet areas despite redwood’s durability. Preventative measures maintain optimal integrity for long service lives.

What natural protections prevent termites in redwood?

Tannins create an unpalatable bitter taste, making redwood less appetizing. Plus, redwood density and compound-filled heartwood deter invasive tunneling into the wood interior. Redwood absorbs moisture slower thanks to extractives, helping reduce decay fungus establishment, leading to termite discovery.

How effective are termiticides and borate treatments on redwood?

Borate solutions and termiticide liquid concentrates like imidacloprid or permethrin soak deep into redwood wood cells thanks to cellular structure. Follow manufacturer-labeled application instructions based on wood thickness and exposure conditions. Reapply chemicals periodically for ongoing protection as directed. Treat cuts end for best absorption.

Do Formosan termites eat redwood worse than native subterranean termites?

Yes, the larger Formosan termite (Coptotermes formosanus) shows greater wood consumption capabilities compared to smaller native species. Testing found Formosans ate over 10x more redwood mass than Eastern subterranean varieties when given a choice. Stopping invading Formosans before infestation establishment is key. Their sheer numbers intensify damage potentials.

How often should I inspect redwood projects for termites?

Conduct visual monitoring of redwood construction elements like deck posts, fences, and retaining walls once every 1-2 years for indicators of termites. Look for new mud shelter tubes beginning from soil sources, swollen softened wood areas, pencil-sized tunnels, discarded wings, or Frass pellets. Probe cracks with an awl to check for live termites. Catching infestations promptly limits damage spread.

Conclusion

Redwood has considerable natural defenses against termites and decay thanks to unique protective compounds within its cellular structure. The dense grain deters the majority of wood-destroying insects. Natural durability gives redwood decking, siding, and landscape timbers long, reliable service lives under normal conditions without supplemental treatments required initially.

However, no wood product lasts indefinitely against the elements. Exterior redwood projects with constant soil moisture contact invite termite colonization faster over time as nutrition is depleted. Supplemental protections help harden redwood against insect threats as environmental exposure accumulates past the 30-year mark. Light-touch preservative treatments avoid compromising the integrity or beauty of redwood projects when correctly applied.

As a homeowner, periodically monitor outdoor redwood construction components for early warning signs of termites – particularly along areas bordering soil. Catching an infestation before major structural damage occurs gives a wide range of treatment options to eliminate pests and prevent further spread. With periodic care and maintenance, a redwood deck or outdoor project will grace your property for generations.