Treating wood to resist termites ranges from factory-applied pressure treatment before construction to surface sprays and localized injections after an infestation is discovered. The right approach depends on whether you’re building new, protecting existing structures, or dealing with active termites already inside your framing. Each method differs in how deeply chemicals penetrate the wood, how long protection lasts, and what it costs.
Pressure-Treated Wood: The Gold Standard
Pressure treatment forces preservative chemicals deep into lumber under industrial conditions, producing wood that resists termites for decades. The American Wood Protection Association’s Standard U1 governs which chemicals are used and at what concentrations, measured in pounds of active ingredient per cubic foot of wood. The most common systems you’ll find at lumber yards are copper-based: Alkaline Copper Quaternary (ACQ) and Copper Azole (CA-B or CA-C). Micronized Copper Azole (MCA) is another widely available option that uses finely ground copper particles instead of dissolved copper.
The concentration of preservative varies by “use category,” which reflects how much moisture and soil contact the wood will face. Wood used for interior framing or above-ground applications needs a lower retention level (0.06 to 0.25 pounds per cubic foot, depending on the chemical), while wood buried in the ground or in constant contact with water requires roughly double to triple that amount. When you’re buying treated lumber, the end tag stamped on each board tells you the use category and preservative type. For deck posts set in concrete, fence posts, or sill plates sitting on a foundation, look for UC4A ratings. For above-ground framing that won’t touch soil, UC3B is sufficient.
Borate-treated wood (sold under several brand names) uses inorganic boron salts and is limited to interior, dry applications. It works well against both subterranean and Formosan termites, with retention levels of 0.17 and 0.28 pounds per cubic foot respectively. But borates are water-soluble, so they leach out of wood exposed to rain or ground moisture. This makes borate-treated lumber a good choice for wall framing, floor joists, and other protected structural members, but a poor one for outdoor use.
Surface Sprays and Brush-On Treatments
If your structure is already built and you want to add termite protection to exposed framing in a crawlspace, basement, or attic, surface-applied treatments are the most accessible option. These products typically contain one of three types of active ingredients: borates (applied as a liquid solution that soaks into bare wood), synthetic pyrethroids like bifenthrin (which repel and kill on contact), or non-repellent compounds like fipronil and imidacloprid (which termites can’t detect, so they walk through the treated zone and carry the chemical back to the colony).
The major limitation of surface treatments is penetration depth. Research on how far preservative solutions soak into lumber found that even after 48 hours of steeping, chemicals penetrated only about 2 to 2.4 millimeters into the wood surface, less than a tenth of an inch. The exact depth depends on the wood species. Radiata pine, which has relatively open grain, absorbed the most. Denser or less permeable species absorbed considerably less. A quick brush or spray application penetrates even less than a 48-hour soak, meaning the protective layer is essentially a thin shell on the wood’s surface.
This matters because termites that enter wood from an untreated face, through a crack, or from a point of soil contact can bypass the treated surface entirely. Surface treatments work best on wood that’s fully accessible on all sides, like exposed joists and rafters, and they need reapplication over time since they don’t penetrate deeply enough to create permanent protection.
Borate Treatments for Existing Structures
Borate solutions deserve separate mention because they’re the most popular DIY wood treatment for termite prevention. When brushed or sprayed onto bare, unfinished wood, the solution soaks in and creates a zone that’s toxic to termites and wood-decay fungi. The EPA classifies boric acid as a Group E carcinogen, meaning there’s evidence it does not cause cancer in humans. It carries moderate acute toxicity for oral and skin exposure (Toxicity Category III), though it can be quite irritating to the eyes.
For residential products, the EPA doesn’t require special protective equipment beyond what’s already on the label. Practical precautions are straightforward: keep children and pets out of the treatment area until the application dries, avoid contaminating food or water sources, and wear gloves during application. Borate treatments are best suited to enclosed spaces like wall cavities (during construction or renovation), crawlspaces, and attics where the wood stays dry. Once the wood gets wet repeatedly, the borates dissolve and wash away.
Localized Injection for Active Infestations
When termites are already inside structural wood, particularly drywood termites that live entirely within the timber, localized injection treatments can target specific galleries without treating the whole structure. A licensed applicator drills small holes into the infested wood and injects liquid insecticides, dusts, or expanding foams directly into the termite galleries.
The effectiveness of this approach depends heavily on accurate detection. If the applicator misses a gallery or underestimates how far the colony extends, the infestation can rebound. UC IPM notes that efficacy is highest when the infestation is accessible and exposed, and when detection equipment (like microwave or acoustic sensors) is used to map the colony’s extent before treatment. The drill holes do cause minor damage to wall coverings and structural members.
Botanical-based injection products like orange oil (d-limonene) and neem oil have been marketed as natural alternatives, but lab and field testing from two universities found their efficacy questionable. Licensed applicators generally use commercial-grade insecticide formulations that aren’t available to homeowners. As UC IPM states plainly, home-use products are not effective for localized drywood termite treatment.
What Professional Treatment Costs
Professional termite treatment for most homes runs $220 to $2,500, with the national average around $575 for a targeted job. The price depends on the scope of work:
- Spot treatment targeting a single wall void or active gallery: $220 to $900
- Full perimeter liquid barrier around the foundation: $5 to $12 per linear foot, or $900 to $2,160 for a typical 2,000-square-foot home with 180 linear feet of foundation
- Whole-house treatment combining a perimeter barrier with interior injections: $1,200 to $2,500
- Tent fumigation for widespread drywood termite infestations: $1,300 to $4,500
DIY liquid termiticides and bait systems use the same active ingredients professionals use and cover a 2,000-square-foot home for $150 to $400 in product cost. The savings are significant, but the tradeoff is application accuracy. A professional perimeter barrier involves trenching along the foundation and injecting termiticide into the soil at precise intervals and depths. Missing a section or applying at the wrong concentration leaves gaps termites will find.
For smaller homes (around 1,200 square feet), professional barrier treatment runs $700 to $1,680, while DIY product cost is $110 to $200. Larger homes around 3,000 square feet see professional costs of $1,100 to $2,640 versus $200 to $400 in DIY product. A hybrid bait-plus-barrier approach done yourself runs $250 to $500 total, compared to $1,500 to $4,500 for the same professional treatment.
Choosing the Right Approach
New construction is the easiest scenario. Specify pressure-treated lumber for all sill plates, rim joists, and any wood within 12 inches of soil. Borate-treated framing for interior walls and floor systems adds whole-house protection at modest cost. These treatments are built into the wood and last the life of the structure.
For existing homes without active termites, a soil barrier treatment around the foundation is the most effective preventive measure. Surface-treating exposed wood in crawlspaces with a borate solution adds a second layer of defense, though its thin penetration depth means it supplements rather than replaces a perimeter barrier.
Active infestations change the calculation. Subterranean termites, which nest in soil and travel up into wood, are best addressed with a professional liquid barrier or bait system that intercepts them at the foundation. Drywood termites living inside the wood itself require either localized injection by a licensed applicator or, if the infestation is widespread, tent fumigation. The choice between spot treatment and whole-house fumigation comes down to how many locations are infested and whether detection equipment can confirm the colony boundaries.