Getting rid of termites inside your walls requires identifying which type of termite you’re dealing with, then choosing between foam treatments injected into the wall void, liquid soil barriers around your foundation, or bait stations that eliminate the colony over time. A localized spot treatment for a single wall runs $200 to $600 if you hire a professional, while whole-home treatments range from $1,000 to $5,000 depending on severity and method.
Confirm You Actually Have Termites
Before you start drilling holes or calling exterminators, make sure termites are the problem. The signs differ depending on the species, but a few indicators are reliable across the board.
For subterranean termites (the most common type), look for pencil-width mud tubes running up your foundation or along interior walls and ceilings. You may also notice BB-sized dots of dried mud on drywall or ceilings. These are “pinholes,” spots where termites accidentally broke through to the surface and quickly sealed the opening with mud. If you scrape one away and watch over a day or two, termites will often repair it, confirming an active infestation.
Sunken, winding trails beneath paint on drywall are another telltale sign. Termites eat the cardboard backing of sheetrock but leave the thin paint layer intact, creating visible depressions or rippled lines along the surface. Tap the wall with a screwdriver handle. Hollow sounds or areas where the tool easily punctures the surface suggest the wood framing behind it has been hollowed out.
Drywood termites leave different evidence. They push tiny, six-sided fecal pellets out of “kick-out holes,” creating small piles of what looks like coarse sand or pepper on floors, windowsills, or countertops below the infested wood. If you find uniform pellet piles near a wall, drywood termites are the likely culprit.
Subterranean vs. Drywood: Why It Matters
The species dictates the treatment. Subterranean termites live in the soil and travel up into your walls through mud tubes. They need constant moisture, so they maintain a connection to the ground. Their damage follows the softer grain of the wood, leaving alternating layers of eaten and uneaten material, with soil packed into the galleries.
Drywood termites live entirely inside the wood itself, with no soil contact. They extract moisture from the wood they digest, so they can infest walls, attic framing, and furniture well above ground level. Their galleries are smooth and clean, filled with those distinctive fecal pellets rather than soil. If your infestation is in an upper-story wall with no mud tubes and pellet piles below it, you’re almost certainly dealing with drywood termites.
This distinction matters because subterranean termites require soil-level treatment (liquid barriers or bait stations) in addition to any wall treatment. Killing the ones inside your wall without addressing the colony underground just buys time. Drywood termites, on the other hand, can sometimes be eliminated with localized wall treatments alone.
Foam Treatments for Wall Voids
Injecting foam termiticide into the wall cavity is the most direct way to kill termites inside a wall. Foam products expand to fill voids and reach deep into termite galleries, coating surfaces that liquid sprays would miss. Some formulations combine two active ingredients for contact kill and longer residual protection.
The process starts with locating the infestation. Use a stud finder to map the framing behind the drywall. If you can see kick-out holes (drywood termites) or pinholes (subterranean termites), drill into those spots with a 1/8-inch bit, then drill additional holes every 8 to 12 inches along the length of the stud to penetrate the termite galleries. Insert the foam nozzle and fill each hole until foam begins to back out.
If you can’t locate the galleries precisely, drill between the studs and foam the entire wall cavity. This is messier and uses more product, but it ensures coverage. The holes are small enough to patch easily with spackle afterward.
Foam treatments work well for contained infestations, but they only kill termites the foam contacts. For subterranean termites, you still need to address the colony’s entry point at the soil level, or they’ll simply find another path into the structure.
Liquid Soil Barriers
For subterranean termites, the standard professional treatment is a liquid termiticide applied to the soil around and beneath your foundation. The chemical creates a continuous treated zone that termites cannot cross without picking up a lethal dose. Modern products use non-repellent formulations, meaning termites don’t detect the chemical and walk right through it, carrying it back to the colony.
This typically involves trenching along the foundation perimeter and, in some cases, drilling through concrete slabs to treat the soil underneath. For an average home with 200 linear feet of perimeter, liquid barrier treatments cost $1,000 to $3,200. The treatment protects the structure for several years, though most companies offer annual inspection warranties.
Bait Stations for Colony Elimination
Bait stations offer an alternative to liquid barriers, particularly when chemical treatment near the foundation isn’t practical (near wells, water features, or sensitive landscaping). Hollow plastic cylinders are installed in augered holes every 10 to 15 feet around the home’s perimeter, flush with the soil surface. Termites tunnel into the stations during their normal foraging, pick up a cellulose-based bait laced with a slow-acting growth disruptor, and share it with nest mates back in the colony.
The slow action is deliberate. If termites died immediately after feeding, others would avoid the station. Instead, the active ingredient prevents termites from completing their molting cycle, killing them weeks after ingestion. This delay gives foragers time to spread the bait throughout the colony.
The tradeoff is speed. Termites can’t see or smell the stations in the soil. They find them by chance during foraging, so weeks or months may pass before discovery. Full colony elimination can take several months or longer. During that time, some additional damage may occur. Initial setup runs $1,500 to $3,000, and most systems require ongoing monitoring fees.
DIY vs. Professional Treatment
Small, clearly localized drywood termite infestations are the most realistic DIY scenario. If you can see exactly where the pellets are falling from and the damage appears confined to one wall section, foam treatment through drilled holes can be effective. The products are available online, and the application is straightforward if you’re comfortable with basic tools.
Subterranean infestations are a different situation. The visible damage in your wall is connected to an underground colony that may be feeding in multiple locations you can’t see. Proper liquid barrier treatment requires specialized equipment for trenching and sub-slab injection, along with knowledge of local soil conditions and foundation types. Bait station systems require consistent monitoring. For subterranean termites, professional treatment is the more reliable path. The average cost runs about $1,500 for initial treatment, with severe cases needing combined methods reaching $3,000 to $5,000.
Preventing Termites From Coming Back
Treatment without prevention is a temporary fix. Subterranean termites are persistent foragers, and the conditions that attracted them the first time will attract them again.
Moisture is the single biggest factor. Water pooling near your foundation creates ideal conditions for subterranean termites. Make sure gutters and downspouts direct water well away from the house. Fix leaking outdoor faucets, pipes, and AC units. Grade the soil so it slopes away from the foundation rather than toward it. In crawl spaces, install a 4 to 6 mil polyethylene vapor barrier over roughly 75% of the soil surface, and ensure vents are clear of debris. Building codes generally call for one square foot of vent opening per 150 square feet of crawl space.
Eliminate wood-to-soil contact anywhere around your home. Wood siding, door frames, and window frames should sit at least six inches above ground level. Pull soil and mulch back from the foundation. If you use mulch in landscaping beds near the house, keep it to a couple of inches deep and never let it touch wood siding or framing. Remove firewood stacks, lumber, cardboard, and any other cellulose material stored against the foundation or inside crawl spaces. Cut back vines, ivy, and dense plantings that touch the house, as these provide hidden bridges that let termites bypass treated soil.
Stumps and dead roots near the foundation are underground food sources that sustain termite colonies close to your home. Remove them where practical, along with any concrete form boards left in place after construction. These small steps make your home a less attractive target and give treatments a much better chance of lasting.