Liquid termiticide soil treatment is the most direct and widely proven DIY method for eliminating subterranean termites. The goal is to create a continuous, unbroken band of termiticide-treated soil around the entire foundation so that workers moving between their underground colony and the wood above the soil line pass through the treated zone. When applied correctly, products containing fipronil additionally deliver a transfer effect: workers that contact the treated soil carry active ingredient back to the colony on their bodies and spread it to nestmates, which can eliminate the colony rather than simply blocking access. Getting the application right requires accurate measurements, correct dilution, and careful attention to the areas where the barrier could be broken, particularly at slabs, hollow block sections, and expansion joints.
Before starting, read the full product label for the termiticide you are using. Label instructions for dilution rate, application volume per linear foot, and required personal protective equipment are legally binding and supersede general guidance. The products compared in the best termiticide guide cover the active ingredients, label requirements, and application differences in detail.
What You Will Need
A successful soil treatment requires a hammer drill with half-inch masonry bits for slab and hollow block injection, a flat spade or trenching shovel for exterior perimeter work, a low-pressure pump sprayer or B&G-style rod injector for applying solution to the trench and injecting through drilled holes, a five-gallon bucket or larger mixing container, chemical-resistant gloves, safety glasses, and a respirator rated for pesticide use. For larger perimeters, a 15 to 25 gallon capacity backpack or pump sprayer significantly speeds application compared to refilling a smaller unit repeatedly.
Step 1: Measure the Treatment Perimeter
Walk the exterior foundation perimeter and record the total linear footage. Include all sides of the structure, including sections that may be partially covered by a deck or adjacent to a garage. Note separately any areas where concrete paving, a porch slab, or a garage slab sits against the foundation, since these require drill-and-inject treatment rather than open trenching. Also note the presence of hollow concrete block foundations, which require rod injection into the block voids, and any expansion joints that may allow treatment solution to migrate away from the intended application zone. Accurate measurement is the foundation of correct volume calculation.
Step 2: Calculate Product Volume Required
Most liquid termiticide labels specify a rate of 4 gallons of diluted solution per 10 linear feet per foot of depth, and the critical detail is that depth means the distance from grade down to the top of the footing, not the depth of the trench you dig. The trench itself is only about 6 inches deep, but the treated soil column extends down to the footing, and the solution is worked into that full depth by applying it to the trench and rodding it into the soil beneath. A footing 2 feet below grade therefore needs roughly 8 gallons per 10 linear feet, not the 2 gallons that the trench depth alone would suggest, so calculating volume from the trench depth rather than the footing depth is a common way to under-apply and leave a barrier that workers can cross. Measure your footing depth, calculate the total volume needed for your full perimeter against the label rate, add volume for any slab injection areas, and mix enough concentrate to complete the full application in one session. Running out of product partway through the perimeter and leaving gaps in the barrier is the most common DIY application error.
Step 3: Dig the Treatment Trench
Excavate a trench 6 inches wide and 6 inches deep along the exterior foundation wall using a flat spade. Keep excavated soil immediately alongside the trench: it will be treated and used to backfill in Step 5. Where established landscaping, paved areas, or structures sit against the foundation and prevent trenching, set these sections aside for drill-and-inject treatment in Step 6. Where the soil is particularly loose or sandy, the trench walls may not hold their shape well; work methodically and apply treatment promptly after opening each trench section.
Step 4: Apply Termiticide to the Open Trench
Pour or spray half the calculated termiticide volume for each trench section into the open trench before backfilling. If using a pump sprayer, apply in a slow sweeping motion to coat the trench walls and floor evenly. If using a rod injector, insert the rod into the trench soil and inject while withdrawing slowly to distribute solution through the soil column. This first application creates the primary contact zone that workers will enter when moving up through the soil toward the foundation.
Step 5: Treat the Backfill and Refill the Trench
Backfill the trench in stages rather than all at once, applying the remaining termiticide volume to each layer of returned soil as you go. Adding a few inches of soil, applying solution, adding more soil, and repeating distributes the termiticide through the full depth of the treated zone rather than concentrating it at the surface. Tamp the backfill lightly with the back of the spade to reduce air pockets, which can create channels where workers bypass the treated zone.
Step 6: Drill and Inject at Slabs, Hollow Block, and Expansion Joints
Concrete slabs, porch floors, garage floors, and hollow concrete block foundations require separate treatment because soil beneath them cannot be trenched from above. Use a hammer drill with a half-inch masonry bit to drill through the concrete at 12-inch intervals along the foundation wall line. Attach a rod injector to a pump sprayer or a B&G tank and inject diluted termiticide through each hole until solution begins to appear at the adjacent hole or until the soil beneath is saturated to the label-specified volume. For hollow concrete block, inject into each block void at the bottom course. After injection, seal all drill holes with hydraulic cement or a comparable masonry filler to prevent water infiltration and to prevent the termiticide solution from evaporating or pooling on the surface.
Expansion joints between a structure slab and the foundation wall, and between a garage floor and the foundation, are among the most common gaps in a termite barrier because the joint provides a direct path from soil to structure. Apply termiticide along the length of each expansion joint at the label rate before treating the adjacent slab sections.
Step 7: Treat the Interior Perimeter if Required
Structures with a basement or crawl space require interior perimeter treatment in addition to the exterior application. In a crawl space with exposed soil, trench and treat the interior face of the foundation wall using the same procedure as the exterior. Treat the soil around any interior piers or posts that contact the ground. In a concrete basement, drill the wall-floor junction at 12-inch intervals and inject as described in Step 6. The label will specify whether interior treatment is required and at what rate for the product you are using.
Step 8: Install Perimeter Monitoring Stations
After completing the liquid treatment, install termite monitoring bait stations at intervals around the perimeter. The liquid treatment provides immediate barrier and transfer-effect protection, but monitoring stations detect any activity that survives the initial treatment or that represents a new colony establishing before the termiticide degrades in the soil. Check stations on a monthly basis for the first year and quarterly after that. Guidance on station selection, placement spacing, and how to identify active termite feeding in a station is in the best termite bait stations guide.
Safety and Re-Entry
Wear chemical-resistant gloves and safety glasses throughout application. A respirator rated for pesticides and organic vapors is recommended for any extended application session. Keep children and pets out of the treatment area until the product has dried into the soil. The product label specifies the re-entry interval after treatment, which is typically a few hours for the treated soil surface. Wash hands, forearms, and any exposed skin thoroughly after completing the application.