Termites cannot eat through metal, solid concrete, fiber cement, brick, aluminum, or naturally resistant woods—teak, redwood heartwood, cypress heartwood, and Alaska yellow cedar among them. Their diet is driven entirely by cellulose, the organic compound in wood and plant matter. Anything without cellulose has no nutritional value to them. The critical qualification: resistant is not the same as impassable. Termites routinely tunnel around materials they cannot eat in order to reach wood on the other side.
For homes built with standard lumber, the most accessible resistant options are pressure-treated lumber—using preservatives like alkaline copper quaternary (ACQ) or copper azole (CA-B), required by building code wherever wood contacts soil—heartwood-grade redwood or cypress for above-ground exterior components, and composite or fiber cement trim and decking.
The bypass problem is real and specific. The Eastern subterranean termite (Reticulitermes flavipes)—the dominant species in Texas—can pass a concrete slab through a gap as narrow as 1/32 of an inch. Metal framing and concrete eliminate the food source; they don't seal every entry point. Subterranean termites also construct mud tubes directly across the face of non-edible materials to reach wood above.
Species determines the relevant risk. Subterranean species, including the invasive Formosan termite (Coptotermes formosanus), attack from the soil up using mud tubes, making the bypass risk structural and often hidden. Drywood species enter from above and target dry structural timber or furniture directly—they don't need soil access, which makes resistant wood and composite materials the more relevant defense against them.
For an existing wood-frame home, resistant materials address future renovations. For the structure as it stands, the most effective layer of protection is a professional treatment program alongside any material upgrades.
Which Resistant Woods Are Backed by Research—and Which Are Overstated
Teak is the most lethal wood to termites of any species studied. In USDA Agricultural Research Service research by entomologists Mary Cornelius and Weste Osbrink, more termites died eating teak than in the group that ate nothing at all for six weeks—indicating active toxic compounds, not just palatability. Redwood had the second-highest termite mortality rate and is the most practical choice for residential construction. The DOE Building America Solution Center lists redwood, incense cedar, black locust, northern white cedar, and Alaska cedar as naturally resistant framing options.
Cedar is frequently overstated. Heartwood-grade cedar resists termites; the softer sapwood near the tree's outer edge does not. Cedar sold without a heartwood specification offers limited protection in practice.
Can Termites Get Through Concrete, Metal, or Fiber Cement?
Concrete, steel, aluminum, brick, and fiber cement contain no cellulose and provide no nutritional value to termites. The EPA recommends concrete foundations with a ventilation gap between soil and wood as a core prevention measure during new construction.
The limitation is entry, not feeding. Subterranean termites build mud tubes across the face of these materials, and R. flavipes can penetrate a crack 1/32 of an inch wide. Fiber cement siding—made from Portland cement, sand, water, and cellulose fibers—is resistant in practice because any trace organic content is encased in an inorganic matrix that termites cannot tunnel through. Metal framing eliminates the structural food source but does not prevent termites from using the structure as a bridge to wooden elements elsewhere.
Pressure-Treated Wood: What the Protection Actually Covers
Pressure-treated lumber is chemically resistant to termites, not immune. The treatment process forces copper-based preservatives—most commonly copper azole or ACQ—into the wood pores under pressure, creating a barrier that also inhibits the fungal decay that attracts many termite species. Most U.S. jurisdictions require it by code wherever lumber contacts or closely approaches the soil line.
Two specific failure points degrade that protection. Any cut end that exposes untreated interior wood becomes a vulnerability; field-applied end-cut preservative is required on treated lumber at soil-contact zones. Pressure-treated plywood also loses its moisture resistance over time—sometimes within a year under sustained exposure—which reduces its effectiveness as a termite deterrent.
For residential pest control services scoping in Texas, understanding where treated lumber ends and standard lumber begins is often what determines the true perimeter of risk in an inspection.
What Termites Chew Through That Surprises Most Homeowners
Termites will chew through thin plastic sheeting, drywall paper facing, foam board insulation, cardboard, and cotton or linen textiles to reach a cellulose food source behind them. They cannot eat these materials for nutrition, but they can penetrate them mechanically.
Standard foam board insulation at the foundation is a documented access risk—termites tunnel through it invisibly. The Concrete Masonry & Hardscapes Association notes that buildings constructed without wood or cellulose products are effectively termite-proof structurally, but most residential homes contain enough mixed materials to create access paths regardless of foundation type.
Mineral wool insulation is one of the few insulation materials with no organic content—the DOE Building America Solution Center lists it as naturally termite-resistant.
When a Material-Only Strategy Isn't Enough
Termite-resistant materials reduce risk. They do not eliminate it, and they do not address a colony that is already established. Six conditions indicate a need for professional evaluation beyond material selection:
- Untreated wood is in direct or partial soil contact anywhere on the property—fence posts, deck supports, porch columns, or buried form boards
- Mud tubes appear on a concrete foundation wall, slab edge, or pier, regardless of whether the concrete itself is intact
- Pressure-treated lumber shows visible decay, discoloration, or moisture damage that signals barrier degradation
- Swarmers or shed wings appear at windows, doors, or baseboards in late winter or spring—R. flavipes and C. formosanus typically swarm from February through May in Central Texas
- Wood probed with a screwdriver produces a hollow sound or soft entry, even without visible frass
- No professional termite inspection or soil treatment has been completed in the past three years
If any of these apply, material choices alone leave the structure exposed. Reviewing animal removal cost benchmarks for the Austin market gives homeowners a framework for what a professional assessment involves before scheduling.
For homeowners in the Hill Country and surrounding communities, termites in Dripping Springs carry the same subterranean species pressure as the city core, with the added variable of expansive clay soils that crack concrete slabs faster and create new access points seasonally. Residents across the metro from Dripping Springs to pest control georgetown deal with the same subterranean species and should account for soil movement when evaluating foundation-level barriers.
FAQ
Q: What is the most termite-resistant wood for a deck or fence?
A: Pressure-treated lumber rated for ground contact is the most practical and widely available choice for either application. For above-ground decking where natural wood aesthetics matter, redwood heartwood had the second-highest termite mortality rate of any wood in USDA ARS testing. Composite decking made from plastic and wood-fiber blends offers resistance without the cost premium of naturally resistant hardwoods.
Q: Can termites chew through plastic?
A: Termites cannot eat solid plastic—it contains no cellulose. They can, however, chew through thin plastic sheeting or vapor barriers when those materials stand between the colony and a wood food source. Rigid PVC, hard composite panels, and fiber cement are mechanically and nutritionally resistant in practice. Soft plastic sheeting used under slabs or in crawl spaces should be treated as a delay, not a barrier.
Q: How do I tell the difference between termite swarmers and flying ants near my home?
A: Termite swarmers have straight antennae, equal-length wings, and a uniform waist. Flying ants have elbowed antennae, two different-length wing pairs, and a pinched waist. Both swarm in spring, and both shed wings near windows. Seeing either near wood or a foundation warrants inspection. For more on how to tell if you have bed bugs versus other pests producing similar interior signs, the same principle applies: species identification determines treatment.
Quick Reference: What Termites Cannot Eat Through
- Termites cannot digest metal, solid concrete, brick, aluminum, fiber cement, or hard plastic—none contain cellulose, the only compound that drives their feeding behavior.
- Teak is the single most termite-lethal natural wood confirmed by research: in a USDA ARS six-week study, termites died at a higher rate eating teak than eating nothing at all.
- Redwood heartwood and cypress heartwood are the most buildable resistant wood options; sapwood from the same trees is not reliably protected.
- Pressure-treated lumber (ACQ or copper azole) is code-required at soil-contact zones, but cut ends and moisture-degraded boards lose their protective barrier over time.
- Concrete and metal eliminate termite food sources but do not seal entry—subterranean termites can pass through a 1/32-inch crack and cross non-edible surfaces via mud tubes.
- Drywood species (Incisitermes minor) bypass soil-level barriers entirely by entering structures from above; resistant woods and composite materials are the relevant defense against them.
- Mineral wool insulation contains no organic material and is listed by the DOE Building America Solution Center as naturally termite-resistant; foam board insulation at the foundation is a documented access route.
- Professional soil treatment remains the most effective protective layer for existing wood-frame homes when paired with resistant material choices in renovations.