16 ANTI-TERMITE TREATMENT (CHEMICAL TREATMENT)
16.1 General
Termites are divided into two types on the basis of their habitat, namely:
- (a) Subterranean or ground-nesting termites
- (b) Non-subterranean or wood-nesting termites having no contact with soil.
The former are more destructive. Treating the soil with chemicals beneath the building and around the foundation with a chemical soil insecticide is a good preventive measure. The purpose of the treatment is to create a chemical barrier between the ground and woodwork. Timber used in the building shall be natural, durable, heartwood, treated, and seasoned.
Anti-termite treatment can also be given, through constructional measures, to existing buildings. These are covered elsewhere (see Chapter 6).
16.2 Site Preparation
16.2.1
Remove trees, stumps, logs, or roots which may be harboring the termites.
16.2.2
On clays and other heavy soils where penetration is likely to be slow and on sloping sites where run-off of the treating solution is likely to occur, the surface of the soil should be scarified to a depth of at least 75 mm.
16.2.3
On loose and porous or sandy soils where loss of treating solution through piping or excessive percolation is likely to occur, preliminary moistening to fill capillary spaces in the soil is recommended.
16.2.4
All subfloor leveling and grading shall be completed. All cuttings, trenches, and excavations vertical surfaces in contact with earth. After the treatment, the earth should be tamped back into place. If the earth outside the building is graded, the treatment should be carried out on completion of grading.
In the event of the filling being more than 300 mm, the external perimeter treatment shall extend to the full depth of filling down to the ground level so as to ensure continuity of the chemical barrier.
16.2.5
All framework, leveling pegs, timber offcuts, or other builders’ debris should be removed from the area to be treated.
16.10 Treatment of Soil Apron Along External Perimeter of Building
The top surface of the consolidated earth over which the apron is to be laid shall be treated with chemical emulsion at the rate of 5 l/m² of the surface before the apron is laid. If the consolidated earth does not allow the emulsion to seep through, holes up to 50 mm to 75 mm deep at 150 mm centres both ways may be made with 12 mm dia rod, on the surface to facilitate saturation of the soil with the chemical emulsion (see Fig. 2.4).
16.11 Treatment of Walls Retaining Soil Above Ground Level
Retaining walls like basement walls or outer walls above the floor level retaining soil need to be protected by providing a chemical barrier so as to prevent entry of termites through voids in masonry, cracks, etc. The soil retained by the walls shall be treated with the chemical emulsion at the rate of 7.5 l/m² of the vertical surface in contact with the soil. This barrier should be in continuation of the barrier up to the plinth level.
16.12 Treatment of Soil Surrounding Pipes, Conduits, etc
When pipes, conduits, enter the soil inside the area of the foundations, the soil surrounding each point of entry should be treated. For this, the soil shall be loosened for a distance of 150 mm and depth of 75 mm and then the treatment should be commenced at the same rate as the foundation soil. When the pipes enter the soil external to the foundation they shall be similarly treated for a distance of 300 mm unless they are clear of the walls by about 75 mm.
16.13 Treatment of Expansion Joints
Expansion joints at ground level are one of the worst hazards for termite infestation. The soil beneath these joints should receive special attention when treatment under 16.6 for plinth filling is being carried out. This treatment should be supplemented by treating the expansion joint after the sub-grade has been laid, at the rate of 2 litres per linear metre.
16.3 Treatment Beneath the Building
For treating soils beneath a building, the following chemicals are effective:
- (a) Heptachlor emulsifiable concentrate 0.5 percent by weight (see IS 6439 : 1978);
- (b) Chlordane emulsifiable concentrate 1.0 percent by weight (see IS 2682 : 1984);
- (c) Chlorpyrifos emulsifiable concentrate, 1.0 percent by weight (see IS 8944 : 1978).
NOTES:
- These chemicals are to be regarded as POISONS. They can have adverse effects on health when absorbed through skin, inhaled as vapors or spray mists, or swallowed. Therefore, they must be safely rigged [see Appendix B of IS 6313 (Part 2) : 1981]. These chemicals should not be used where there is a risk of wells or other water supplies being contaminated. The Authority concerned shall be consulted.
- Aldrin has been banned by the Government of India. Before use of these chemicals, the latest recommendations of the Central Insecticide Board and Registration Committee, Ministry of Agriculture, Faridabad should be referred.
16.3.1
Where there are mounds of termites within the excavated area, these chemicals shall be poured into the mounds at several places after breaking them. The quantity used shall be related to the size of the mound. For a mound of about 1 cm³, 4 l of the emulsion of one of the chemicals may be used, namely:
- 0.25 percent Heptachlor emulsifiable concentrate.
- 0.5 percent Chlordane emulsifiable concentrate.
16.4 Time of Application
Soil treatment should start when foundation trenches and pits are ready to take mass concrete in foundations. Treatment should not be carried out when it is raining or when the soil is wet. This also applies to filled-up soil within the plinth area before laying the subgrade for the floor.
16.5 Treatment of Masonry Foundations and Basements
16.5.1
The bottom surface and sides (up to about 30 cm) of the excavations made for necessary foundations and basements shall be treated with the chemical at the rate of 5 l/m² of surface area.
16.5.2
After the masonry foundations and retaining wall come up, the backfill in immediate contact with the foundation shall be treated with the chemical at the rate of 7.5 l/m² of the vertical surface of the sub-structure for each side. If water is used for ramming the earth fill, the chemical treatment shall be carried out after the ramming operation is done. For this, rodding of earth close to the wall at 15 cm centres shall be done and working the rod backwards and forward parallel to the wall before applying the chemical emulsion.
The earth fill is done in layers and the chemical treatment shall be carried out for each layer. After the treatment, the earth should be tamped in place. The chemical emulsion shall be directed towards the masonry surfaces in contact with the earth. All foundations shall be fully surrounded by and in close contact with the chemical-treated soil barrier (see Fig. 2.3 and Fig. 2.4).
16.6 Treatment of RCC Foundations and Basements
The treatment of masonry foundations was necessary because of the voids in joints through which the termites are able to seek entry into the building. However, in RCC foundations, there are no such voids for the termites to penetrate. It is therefore unnecessary to start the treatment of RCC foundations from the bottom. The treatment may be started at 500 mm below ground level except when the level is raised or lowered by filling after the foundations have been cast. In such a case, the depth of soil level shall be determined from the new ground level. The soil in the immediate contact with RCC shall be treated with 7.5 l/m² of the chemical. The other details are as in Fig. 2.5.
16.7 Treatment of Top Surface of Plinth Filling
16.7.1
The top surface of the consolidated earth within plinth walls shall be treated with chemical emulsion at the rate of 5 l/m² of the surface before the sandbed or sub-grade is laid. If the filled bed is rammed and the surface does not allow the emulsion to seep through, holes up to 50 mm to 75 mm deep at 150 mm centres both ways may be made with 12 mm steel rod to facilitate saturation of the soil with chemicals.
16.8 Treatment at Junction of the Wall and the Floor
Special care shall be taken to establish continuity of the vertical chemical barrier on the inner wall surfaces from ground level (or other level) up to the level of the filled earth surface. To do this, a small channel 30 mm × 30 mm shall be made at all the junctions of wall or columns with the floor (before laying sub-grade) and rod holes made in the channel up to the ground level 150 mm apart; the rod shall be moved backward and forward to break up the earth and then the chemical emulsion be poured along the channel at a rate of 7.5 l/m² of the vertical wall or column. This would permit the soil to be soaked right down to the bottom. The soil should be tamped back into place after the operation.
16.9 Treatment of Soil Along External Perimeter of the Building
After the building is complete, the earth along the external perimeter of the building shall be rodded at intervals of 150 mm to a depth of 300 mm. The rod should be moved backward and forward parallel to the wall to break up the earth and the chemical emulsion be poured along the water at the rate of 7.5 l/m² of the.
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