Methods of Termite-Proofing

Termite-proofing methods may be grouped under the following two categories:

1. Soil treatment with chemicals
2. Structural barriers

1. Soil Treatment with Chemicals

(i) Chemicals for Treatment

Following are the emulsifiable chemicals recommended in BIS code:

1. Chloropyrifos concentrate 1% by weight
2. Heptachlor concentrate 0.5% by weight
3. Chloride concentrate 1.0% by weight

Chloropyrifos has been widely used. They are available with agrochemical agencies which are used to control termites in crops. This chemical with 1% concentration is mixed in water for soil treatment and in kerosene oil for treatment of wood. As the solution is toxic, it should be washed immediately by soap and water, if it comes into contact with part of the body.

(ii) Pre-Construction Treatment

Treatment should be started when foundation trenches and pits are excavated to the size and level. Treatment should not be done when the soil is wet due to rain or sub-soil water. Further, the treated area should not be disturbed. The treatment is performed in soil in five stages as discussed below.

In the first stage, treatment of wall trenches and basement excavation are done. If termite hills are noticed at the site during site clearance chemicals should be sprayed first. All side surfaces of trenches/pits and bottom of wall trenches/pits and basement excavations should be treated to a height of 30 cm from the bottom. The usage of solution should be at the rate of 5 l/m² of surface area (Fig. 29.1).

In the second stage, treatment of refill in contact with foundation is attended. All the refill earth in the excavation immediately in contact with both sides of the wall footing should be treated (Fig. 29.1) for a distance of 30 cm. Similarly all the four sides of a column should be treated and treatment should be at the rate of 3–5 l per linear metre vertical surface of the wall.

Figure 29.1 Anti-termite treatment of load bearing wall foundation

The third stage is treatment of soil below floors. The earth fill below the floors up to the plinth level has to be treated after the fill has been made. This is performed by making holes 5–7.5 cm deep at 15 cm centres in a grid pattern. The holes are filled with the solution at the rate of 5 l/m² of treated surface (Fig. 29.1).

The fourth stage consists of treatment of junction of floor and wall. Before laying the sub-grade, channels of 3 cm wide and 3 cm deep are dug along the junctions of floor and wall. Along the channel, holes at 15 cm apart are made and treated at 15 l/m² of the wall surface and the chemical is allowed to seep through the bottom. The soil is tampered back in position after the operation (Fig. 29.1).

The fifth stage is treatment of soil along external perimeter of the building. After the completion of building, holes are made along the external perimeter at intervals of 15 cm and to a depth of 30 cm. These holes are filled with the chemical emulsion at the rate of 5 l/m length of wall (Fig. 29.1).

Apart from treating the soil, it is also important to treat the expansion joints, soil around the pipes and conduits and wooden surfaces for a complete protection from termite.

2. Structural Barriers

In order to prevent the termites’ entry through walls, impenetratable physical structural barriers may be provided at the plinth level continuously. Such a structural barrier is generally of concrete or sometimes metal. The cement concrete may be from 50 to 75 mm thick. It is recommended to project about 50–75 mm internally and externally. The metallic materials may be sheets of non-corrodible one, such as copper or galvanised iron with a thickness of 0.80 mm.