Which Woods Naturally Stop Termites? A Materials Science Guide

Choosing wood for an outdoor project or a piece in a termite-prone area means asking more than just how it looks or works. You need to know which species have built-in defenses and why their physical properties make them durable.

This guide breaks down the science and shop reality. We will cover the specific species with natural termite resistance, how density and Janka hardness physically block insects, the role of natural extractives and oils, and practical selection tips for your next project.

My advice comes from testing these woods in my own shop and studying their material properties to separate marketing hype from measurable performance.

How Wood Fights Back: The Science of Natural Termite Resistance

What makes a wood termite resistant? It boils down to two main strategies: physical density and chemical weapons. Think of it like a fortress. Dense wood is the thick, formidable wall. Chemical extractives are the poisoned moat.

Janka hardness is a wood’s crunch resistance, a direct measure of how tough it is to dent or wear down. A high Janka number means termite mandibles, which are like tiny chisels, wear out quickly trying to tunnel through it. Specific gravity measures a wood’s solidity compared to water. A high specific gravity means less air space and porosity inside the wood.

Termites need moisture and find porous wood easier to digest. Dense wood is a dry, tough meal that breaks their tools. The chemical defense comes from natural extractives like oils, resins, and tannins. Some woods even have microscopic silica crystals that act like glass shards, grinding down insect mouths.

Here is the critical shop truth you must remember. No wood is 100% termite-proof forever. Under the right conditions of constant moisture and pressure, any wood can be compromised. Our goal is to pick woods that make the termites’ job so difficult they give up and look for an easier meal, like your neighbor’s pine fence.

Material Property Deep Dive: Janka and Specific Gravity

Let’s make these numbers mean something in your shop. The Janka hardness test measures the force needed to embed a 0.444-inch steel ball halfway into the wood. I think of it as testing the wood’s armor plating. A low number means soft armor.

Specific gravity tells you about porosity. Water has a specific gravity of 1.0. A wood with a specific gravity of 0.50 is half as dense as water. It’s like a sponge compared to a brick. Lower porosity means less internal moisture, which is a huge turn-off for termites seeking a damp home.

Look at the scale. A common softwood like Southern Yellow Pine has a Janka rating around 690 lbf. It’s decent for framing but a termite banquet. Now, look at Ipe, a tropical hardwood. Its Janka rating is near 3500 lbf. That’s over five times harder. For a termite, chewing through Ipe is like trying to eat concrete with plastic utensils. The difference isn’t subtle.

Naturally Resistant Woods: A Shop-Tested Guide

This list focuses on woods you can actually find and use. I’ve milled, sanded, and finished each of these. Their properties aren’t just from a textbook, they’re from my bench.

Teak: The Golden Standard

Teak’s defense is its legendary oiliness. It’s all about the chemical moat. The natural oils, primarily tectoquinones, are toxic to fungi and insects. These oils also stabilize the wood, minimizing swelling and shrinking. That’s why it’s the king of high-end outdoor furniture and boat decking.

Can teak wood get termites? Yes, but it’s very unlikely in a well-maintained piece. The oils are the primary shield. Over decades, surface weathering can deplete these oils, making old, neglected teak slightly more vulnerable. A light sanding and oil refresh can often restore its protective barrier.

• Janka Hardness: 1000-1150 lbf
• Specific Gravity: 0.55-0.70
• Notable Toxins/Extractives: High natural oils (tectoquinones)
• Stability/Movement: Very stable, low movement

Shop Tip: Wear gloves when working teak. The oils can cause skin irritation for some, and they will contaminate your sandpaper quickly. Use sharp carbide tooling, as the silica content will dull steel blades fast.

Ipe and Tropical Hardwoods: The Density Kings

With Ipe, Cumaru, and Massaranduba, physics is the primary defense. These woods are so dense they sink in water. Their incredible hardness is a physical barrier that exhausts termites. They also contain various natural extractives that add a chemical deterrent.

The trade-off is in the working properties. Ipe is famously tough on tools; you will need carbide-tipped blades and bits, and pre-drilling for fasteners is mandatory. Its extreme density also means it holds heat, so it can get very hot in direct sun, a consideration for decking.

• Janka Hardness (Ipe): ~3500 lbf
• Specific Gravity (Ipe): 0.90-1.05 (often sinks)
• Notable Toxins/Extractives: Various extractives, high silica content
• Stability/Movement: Excellent dimensional stability

Shop Tip: When cutting or sanding Ipe, the dust is a severe irritant. A high-quality respirator and dust collection are non-negotiable, not a suggestion.

Cedar and Redwood: The Aromatic Softwoods

Here, the defense is almost entirely chemical. Western Red Cedar and Redwood are quite soft (low Janka), but they are packed with aromatic compounds like thujaplicins. These act as powerful natural preservatives and insect repellents.

Their perfect use is in outdoor structures, garden beds, and closet linings where their scent creates a zone of protection. For patio furniture, their low density makes them easy to move, but they will dent and weather to a soft gray if left unfinished. They are not for high-wear surfaces like a deck floor.

• Janka Hardness (W. Red Cedar): ~350 lbf
• Specific Gravity (W. Red Cedar): ~0.32
• Notable Toxins/Extractives: Thujaplicins, volatile aromatics
• Stability/Movement: Good stability, low shrinkage

Shop Tip: The heartwood is the resistant part. Avoid using the pale, fast-grown sapwood in any critical outdoor application, as it lacks these protective chemicals.

White Oak and Locust: The Domestic Durable Options

For furniture and interior projects where you want domestic hardwoods, White Oak is a top choice. Its resistance comes from a mix of good density and high tannin content. Critically, White Oak has cellular structures called tyloses that plug its pores. This makes it much more water and rot-resistant than Red Oak, which lacks tyloses. A closer look at white oak vs red oak anatomy shows how tyloses and vessel size shape porosity. These anatomical differences help explain their moisture resistance and durability.

For extreme outdoor durability in posts or ground contact, Black Locust is a domestic superstar. It’s harder than White Oak and rivals many tropicals in rot resistance. White Oak’s plugged pores give it a natural edge for outdoor furniture where moisture is a concern, far outperforming its red cousin.

• Janka Hardness (White Oak): ~1360 lbf
• Specific Gravity (White Oak): ~0.68
• Notable Toxins/Extractives: High tannin content
• Stability/Movement: Moderate movement, good for its hardness

Shop Tip: When finishing White Oak for outdoor use, a simple oil finish (like tung or linseed) highlights the grain and allows the tannins to continue providing some protection. This same oil-finish approach translates well to indoor wood furniture, where wipe-on applications highlight the grain and help protect the wood. Film-forming finishes can trap moisture if they crack.

Pressure-Treated Wood and Other Man-Made Defenses

First, let’s clear up the big question. Can termites eat pressure treated wood? The short answer is no, not if it’s properly treated to modern standards. The same goes for carpenter ants. These treatments are insecticides.

Modern treatments like micronized copper or copper azole work by making the wood toxic. The preservative is forced deep into the wood’s cells under high pressure. When termites or fungi try to consume it, they ingest the copper, which is poisonous to them. This pressure treatment is the most reliable man-made defense for wood in direct contact with the ground, like deck posts or fence poles.

But there’s a critical detail every woodworker must know. Treatment primarily protects the sapwood-the outer, living part of the tree. If you cut a treated board, you expose the untreated inner heartwood at the ends. This fresh surface can be vulnerable. For critical cuts, you should brush on a copper-based preservative gel made for end cuts.

This is where natural resistance has an edge. The heartwood of a species like Eastern Red Cedar or Teak is resistant all the way through. Saw it, drill it, carve it-the protection goes with it. A treated pine 4×4 has a chemical shield. A cedar 4×4 has a built-in defense.

You might see products labeled “termite resistant wood polish” or sealer. Think of these as raincoats, not armor. They create a surface barrier that can deter casual chewing and block moisture, which attracts pests. A surface finish is a good maintenance step, but it can be scratched or worn through; it’s not a substitute for using a resistant wood or proper pressure treatment for high-risk applications.

Choosing and Using Resistant Wood for Your Project

Your project type dictates the best balance of resistance, cost, and workability. Here’s how I break it down in the shop.

Furniture (Indoor & Outdoor)

For indoor furniture, you rarely need heavy termite resistance unless you’re in a severe infestation area. Focus on durability and beauty.

• White Oak (1360 Janka): Excellent for indoor pieces. Its tyloses-closed pores make it naturally rot and insect resistant. A classic for cabinetry and tables.
• Western Red Cedar (350 Janka): Perfect for hope chests, blanket boxes, or closet linings. Its aromatic oils repel moths and insects. It’s soft, so it dents easily-ideal for low-wear items.
• Teak (1155 Janka) or Ipe (3680 Janka): The premium choices for outdoor furniture. Their high natural oil content shrugs off water and insects. Ipe is incredibly hard; use carbide tools and pre-drill for fasteners.

Flooring

Flooring needs hardness first. Termite resistance is a bonus for ground floors.

Brazilian Cherry (2350 Janka) is a top contender here-extremely hard, dense, and naturally resistant. White Oak is again a superb, more available choice. For a softer, aromatic option, Eastern Red Cedar (900 Janka) can work for bedroom floors, but expect more wear and tear.

Patio & Decking

This is the front line. Wood here is exposed to everything.

• Pressure-Treated Southern Yellow Pine: The most common and cost-effective. Ensure it’s rated for ground contact if used for structural posts.
• Tropical Hardwoods (Ipe, Cumaru, Tigerwood): Offer the best natural performance. They are expensive and challenging to work with but last decades.
• Domestic Options: Western Red Cedar and Redwood are good for above-ground structures like deck boards and rails. They have moderate hardness but good resistance. Keep them off direct soil contact.

Framing and Structure

For termite resistant wood for framing, you generally have two paths. For standard house framing in termite-prone regions, builders use borate-treated lumber. Borates are diffuse into the wood and are toxic to insects but have low toxicity to mammals. It’s a good preventative.

For sills, mudsills, or areas of high risk, switching to a naturally resistant species like Eastern Red Cedar for the sill plate can create a durable barrier. It’s more expensive but provides peace of mind and full-depth protection that won’t leach chemicals.

Essential Maintenance Tips

No wood is invincible. Resistant wood still needs smart practices. Always keep wood dry and ensure good ventilation. Maintain at least a 6-inch gap between any wood and soil. Fix leaky faucets or gutters immediately, as moisture is the primary attractant for decay fungi, which softens wood and invites insects.

Troubleshooting a Suspected Infestation

If you find damage despite using a “resistant” wood, check two things. First, are you sure it’s the heartwood? Sometimes lumber contains a mix of sapwood and heartwood. Second, check for excessive moisture. Probe the damaged area with a screwdriver. If it’s spongy and wet, you have a moisture/rot problem that compromised the wood’s natural defenses, making it palatable to pests. The solution always starts with finding and eliminating the source of moisture.

The Cellular Mechanism of Action: Why It Works

Termites and decay fungi are looking for the same thing: an easy meal. The woods they love, like pine or poplar, are essentially a buffet of digestible cellulose and hemicellulose held in a soft, accessible structure. Resistant woods change that recipe entirely, making the meal either toxic, impossible to digest, or too physically tough to bother with.

The Chemical Defense: Extractives

Think of extractives as a tree’s built-in preservative system. These aren’t part of the structural cell walls. As the tree matures, it produces complex oils, resins, alkaloids, and tannins that are deposited in the cell lumen (the hollow space inside the cell) and within the cell wall itself.

I think of it like seasoning wood from the inside out. When you cut into a fresh piece of cedar, that distinctive smell is the evaporating oils. For a termite, that smell is a warning sign.

• Toxicity: Compounds like thujaplicins in cedar and tannins in black walnut are antifungal and insecticidal. They disrupt digestion or are outright poisonous to microorganisms and insects.
• Water Repellence: Oils in teak and cedars make the cell walls hydrophobic. This reduces moisture absorption, which is critical because fungi and many insects require a certain moisture level to thrive.

In the shop, you see this in action when your tools gum up or when a finish won’t adhere properly to oily woods like teak without a solvent wash.

The Physical Defense: Density and Silica

If chemicals are the seasoning, density is the toughness of the cut. A high Janka hardness rating and specific gravity (density relative to water) tell you the wood has thick cell walls and tiny pores. Pine often ranks lower in both Janka hardness and density compared to hardwoods.

This creates a simple physical barrier. There’s less digestible material per cubic inch and less air space for moisture-the perfect conditions for rot-to reside. Termites expend immense energy for little nutritional return.

Some tropical woods, like ipe and many bamboos, add a secret weapon: silica. This is essentially microscopic, glass-like particles embedded in the fibers. As insects chew, the silica abrasively wears down their mandibles, making feeding inefficient and unsustainable for the colony.

The Practical Analogy: Bread vs. Beef Jerky

Picture a loaf of fresh white bread. It’s soft, airy, and easy to eat. That’s pine to a termite.

Now picture a piece of dense, heavily peppered beef jerky. It’s tough to tear, requires serious chewing, and the pepper makes it unpleasant. That’s ipe or old-growth heartwood cedar.

The peppery seasoning represents the toxic extractives. The tough, dense texture is the high Janka hardness and specific gravity. A termite, given the choice, will always go for the bread.

What This Means for Your Project Selection

This science isn’t just academic. It guides material choice. For a ground-contact planter box, you need both chemical and physical defenses-that’s where a dense, oily wood like white oak or cedar heartwood shines.

For indoor furniture, chemical resistance from woods like black walnut may be sufficient. Always prioritize the heartwood, the older, inactive core where these protective extractives are most concentrated. The outer sapwood of any species is always vulnerable.

Remember, no wood is immortal. This natural resistance is a delay tactic, measured in decades, not a guarantee for eternity, especially in severe conditions.

Frequently Asked Questions: Termite Resistance in Practice

Can a polish or sealer make any wood termite-proof?

No, finishes only create a temporary surface barrier against moisture and casual chewing. For lasting resistance, you must select wood with inherent density or extractives, as a sealer can be compromised through wear or damage. Even your food oils will only penetrate but not provide lasting protection.

What is the best termite-resistant wood for structural framing?

For modern framing, borate-treated lumber is the standard, effective solution. For critical sills or plates, naturally resistant heartwood like Eastern Red Cedar provides full-depth, non-leaching protection, though at a higher cost.

How do I balance Janka hardness and termite resistance for flooring?

Prioritize high Janka hardness (e.g., Brazilian Cherry, White Oak) as it provides both wear durability and a physical barrier to insects. When comparing hardwood and softwood, Janka hardness is a key factor in determining durability and suitability for a given application. Ensure the species also contains natural extractives for complementary chemical defense.

Does termite-resistant furniture require special maintenance?

Maintenance focuses on preserving the wood’s natural defenses; for oily woods like teak, periodic cleaning and light oiling replenish surface protectants. Always ensure joinery and end grains are well-sealed to prevent moisture ingress, which can undermine resistance.

What are the most accessible termite-resistant woods in the Philippines?

Locally sourced hardwoods like Narra (Janka ~1290 lbf) and Yakal (Janka ~2020 lbf) offer excellent density and natural extractives. Their high specific gravity and silica content provide a robust physical and chemical defense suitable for the local climate.

Selecting Woods That Resist Pests Naturally

Janka hardness and density are the most reliable material properties for predicting natural termite resistance. Woods like ipe or teak have dense, interlocked grains that physically deter insect penetration. In your shop, use these species for outdoor furniture, decking, or any project near ground contact to significantly reduce pest risk. From my experience, even the most resistant wood performs better when paired with precise joinery and a protective finish.

Source your lumber from certified sustainable forests to advocate for ethical harvesting and ecosystem health. Continuously test and learn how different woods behave in your local environment to refine your material choices.

Sources and Additional Information

• Termite Prevention: What Wood Will Termites Not Eat? | Orkin
• The 7 Best Termite-Resistant Woods for Your Next Project – AdvantageLumber Blog
• USDA ARS Online Magazine What “Wood” a Termite Prefer To Eat?
• r/Home on Reddit: How to make untreated wood waterproof as well as termite-proof?
• Termite Resistant Wood for Home Construction Use – MexConnect
• Wood – Termite Resistant – Building Materials – The Home Depot
• These 5 Termite Resistant Types of Woods Could Save Your Home
• What kind of wood should be used for framing a house to prevent termites? – Quora