By Amado de Jesus
Inquirer

MANILA, Philippines–Termites are everyone’s nightmare. They are the most destructive wood insect in the world. Subterranean termite species live in large colonies underground and affect houses, buildings and cellulose-based products. Most of these species thrive in the tropics and warm temperate coastal and inland regions.

Subterranean termites enter structures by tunneling in through the soil. There are several ways they can gain access to wooden parts of a structure. They can tunnel through timber in contact with the soil; they can make shelter tubes along foundation walls; and they can make shelter tubes through a crack or void space. The key therefore to termite control is finding a way to block off these entry points by installing barriers.

Some of the most common termite control barriers are soil poisoning using pesticides, physical barriers around the house, a combination of the two or the bait and monitoring systems.

Soil poisoning

The new generation of soil treatment is water-based.

This is in contrast to earlier chemicals like Chlordane, which have been banned in the market because they were toxic and stayed in the soil for many years. This new type of treatment chemicals must be applied by licensed pest control professionals.

Bait, monitoring systems

The bait and monitoring system consists mainly of placing wood baits around the house at regular intervals of about ten feet. The baits are monitored every two weeks and once termites are detected, they are replaced with termiticide baits.

The termites carry these baits back and feed them to the rest of the colony, eventually killing the termites.

Physical barriers

An effective environment-friendly and nontoxic method of termite control is the installation of physical barriers around the house.

One type of physical barrier is a termite shield which is simply a sheet of noncorroding metal with a projecting 1″ lip bent down at a 45-degree angle capping the foundation wall or support.

The other types are stainless steel mesh barrier and waterproof membrane barriers. These types of barriers, like the termite shield, are also installed in a similar manner.

The fourth type is the sand barrier which is easy to install and most effective when placed during construction. In some countries a six-inch layer of barrier sand is laid out instead of crushed gravel beneath the slab. The barrier sand could be used as backfill next to the foundation walls with provisions for a good drainage system.

Why sand barriers?

The idea behind the use of sand as an effective termite control is that sand particles help block termites.

Termites use their mouth parts rather than their legs to dig their way through the soil. They are unable to move particles larger than 1 mm. As the sand particles increase in size so does the void space between the particles. Termites can crawl through gaps or spaces between particles sized 3mm and above. Therefore, to block termites the effective particle size is about 1 to 3 mm.

Coarse sand with particles within this size range can be used as a barrier around the foundation of a house to protect against subterranean termites. It can also be used in perimeter trenches, crawl spaces, inside hollow block voids, around the bases of fence posts, poles, piers, porches, decks and retaining walls.

Installation of sand barriers

If the sand barrier is installed before construction it is placed below the concrete slab as a base material. For footings, however, sand barriers cannot be placed underneath since footings must rest on solid undisturbed ground. If installed after construction, the sand barrier is placed as a trench alongside the foundation wall. An adequate surface drainage must be provided to ensure minimal drainage of surface water into full depth trenches.

Barriers can be 4″ or 6″ thick extending all the way to the footing. It must be compacted at intervals of every two feet to prevent settlement. The top of the sand barrier can be left exposed or, where pedestrian access is required, covered with concrete slab, bricks or stone blocks to form a walkway.

Advantages of sand barriers

The prevalent method of subterranean termite control relies on the use of chemicals to poison the soil, thus creating a protective seal or barrier around the structure.

A sand barrier is more effective than a chemical barrier since it does not require a repetitious application. The sand barrier also has an environmental advantage in that it does not pose a health hazard to humans either through direct contact of the chemicals or through soil and water contamination.

Sand barriers save the homeowner the costs of chemical reapplication and maintenance contracts for the chemical pesticide treatment.