Learn which plants thrive in your Hardiness Zone with our new interactive map!

How to Trench for Termites

By Dannah Swift ; Updated September 21, 2017

Termites are notoriously difficult to kill. Once they detect a poison in the midst, they will dig new tunnels around it and continue to eat any cellulose fibers they can find. Since 1999 a termite treatment developed by entomologist Mike Potter called "trenching" has proven very effective in the war on termites. Trenching involves digging a 4- to 6-inch trench along the foundation of your home and filling it with an undetectable, non-repellent termiticide solution. Termiticide is passed throughout the colony each time a termite passes through the barrier, effectively killing all of them.

Trench for Termites

Count up the number of linear feet you are going to treat. For large areas, it helps to have a measuring wheel, which tallies up the distance around a space while you walk. You will need these measurements to administer the proper amount of termiticide. Include any concrete slabs, such as patios and garages, and include crawl spaces inside and out.

Using a trenching tool, dig a trench 6 inches wide and 6 inches deep along the foundation of the building you are treating. Dig a trench all the way around the perimeter.

Treat at a rate of 4 gallons every 10 feet. Remember that you will need to treat both the inside and outside of the crawl space.

Fill the trench with 4 gallons of termiticide solution (i.e., termiticide and water) per 10 feet. Use the 5-gallon bucket to measure out 4 gallons repeatedly.

After filling the trench, replace the dirt you removed from the trench. If the termiticide solution has already seeped into the soil, you'll need to treat the backfill as well, but if it has not, it should soak up the solution just fine.

Next, treat any contiguous cement slabs, such as the garage, porches and patios. Using a hammer drill with a 12-inch by ½-inch bit, drill holes in the slabs 3 to 4 inches away from the wall or foundation and every 10 to 12 inches. You will need to reach the dirt beneath the slab in order for the treatment to sink in, so a 12-inch bit is necessary.

Use the 1-gallon sprayer on the pin stream setting to target the hole precisely, and avoid splashing. Fill at 4 gallons per 10 feet.

Fill the holes with concrete filler or ½-inch plugs or corks, available at any home improvement store.

Treat the interior of the crawl space at the same rate as the exterior and pay special attention to the area surrounding the supporting piers.

If the building stands on hollow concrete blocks, treat every void starting at the second block from the bottom (no closer than 18 inches from the ground). Treat at 2 gallons per 10 linear feet.


Things You Will Need

  • Trenching tool
  • Shovel
  • Hose-end sprayer
  • 5-gallon bucket
  • Water
  • Termiticide (Termidor, though pricey, has the transfer effect you want)
  • Hammer drill
  • Cement plugs or filler


  • Termidor is odorless, tasteless and will not harm pets or humans. That said, read the directions carefully and strictly follow them.



About the Author


Based in Fort Collins, Colo., Dannah Swift has been writing since 2009. She writes about green living, careers and the home garden. Her writing has appeared on various websites. She holds a Master of Arts in English literature from the University of New Hampshire and is currently pursuing a certificate in paralegal studies.