HOW TO DO ANTI-TERMITE TREATMENT FOR YOUR HOME FOUNDATION?

ANTI-TERMITE TREATMENT OF FOUNDATIONS

The subject of anti-termite treatment of buildings is usually divided into the following three parts:

1. Pre-construction measures to be taken

2. Pre-construction treatment

3. Post-construction treatment

 

IS 6313 Part 1 deals with the general constructional measures to be taken, Part 2 deals with pre-construction treatment and Part 3 discusses post-construction treatment (treatment of existing buildings). They give many constructional features to be provided in buildings such as for godowns, etc. to reduce termite attacks which we will not deal with in this book. Here we will consider only pre-construction and post-construction treatments of ordinary buildings.

 

Termites in Buildings

Based on their habitat, termites are classified into the following two types:

1. Ground nesting or subterranean termites

2. Wood nesting or non-subterranean termites

Ground nesting or subterranean termites are more common in India and their presence in and around a building is indicated by swarms of winged reproductions flying from the soil or wood lying around the site just at the beginning of the monsoon.

 

Wood nesting or non-subterranean termites live in the dry wood inside buildings and is recognized by their pellets of digested food or blisters on the wood surface as the wood is eaten away. In their search for food, these termites damage not only wood (cellulose) but also substances like rubber, plastic, underground cables, etc. Both varieties can be terminated by the same anti-termite chemicals.

 

Recommended Chemicals for Treatment

Even though Aldrin, DDT and many other chemicals were once prescribed in old IS codes, many of them were found to be very toxic and leave toxic residues in the soil and ground walls which give health problems over a period of time. Hence many of them have now been banned in the new revision of the BIS code. The following emulsifiable chemicals have now been recommended:

1. Chloropyrifos concentrate 1.0% by weight

2. Heptachlor concentrate 0.5% by weight

3.  Chlordane concentrate 1.0% by weight

 

Chlorpyrifos in 1% concentration by weight conforming to IS8944 (1978) is a popular chemical being used. They are available with agrochemical agencies as they are used to control termites in crops such as cotton, coconut, citrus, etc. Durmet is a brand name of one of the chlorpyrifos available in the market in various concentrations. Another brand name is Dustban TC. These can be diluted to form 1% concentration as desired in water for soil treatment and in kerosene oil for treatment of wood.

 

Generally, 5 parts of Durmet 20 EC are diluted with 95 parts of water (or kerosene) to give an emulsion of 1%. As the solution is toxic, if it comes in contact with the skin, it should be washed out immediately with soap and water. The methods of treatment (pre-construction treatment and post-construction treatments) are briefly described below.

 

Pre-construction Treatment with Durmet

A hand-operated pump is used for uniformly spraying the chemicals at the specified rate. To facilitate the right dose, graduated containers should be used. Treatment should not be carried out when it is raining or soil is wet with subsoil water. It should start when foundation trenches and pits are ready and just before concreting of the foundation. The treated barriers for termites should not be disturbed after treatment. The treatment is shown in Fig. below and is carried out in seven stages as described further.

First stage: Treatment of wall trenches and basement excavation. As the first step, all termite hills found at the site during site clearance should be sprayed with chemicals. All surfaces of pits (sides and bottom of wall trenches and basement excavations) should be treated to a height of 30 cm from the bottom with the solution at the rate of 5 litres per square metre of surface area.

Anti-termite treatment of foundation and earth fill below the ground floor.

Second stage: Treatment of refill in contact with the foundation. All the refilled earth in the excavation is immediately in contact with both sides of the wall footing and all four sides of a column footing should be treated for a distance of 30 cm (as shown in Fig. above) at the rate of 3 to 5 litres per linear metre vertical surface of the wall. If water is used for ramming the earth, then treatment should be done after the consolidation by rodding (making holes) in the consolidated earth at close intervals of 15 cm close to the wall or columns and applying the chemical close to the wall. It is preferable to treat all the earth adjacent to the foundation for a width of 30 cm. Similarly in framed structures, excavations for the plinth beams should also be treated.

 

Third stage: Treatment of soil below floors. The earthfill below the floors up to the plinth level has also to be treated after the fill has been made by putting holes 5 to 7.5 cm deep at 15 cm centres in a grid pattern and filling the holes with the solution at the rate of 5 litres per square metre of the treated surface.

 

Fourth stage: Treatment of junction of floor and wall. Before laying the subgrade, channels of 3 cm wide and 3 cm deep are dug along the junctions of floor and wall and treated at 15 litres per square metre of wall surface by putting holes 15 cm apart along the channel and allowing the chemical to seep through to the bottom. The soil is tamped back in position after the operation.

 

Fifth stage: Treatment of soil along the external perimeter of the building. After the building is completed, holes are made along the external perimeter at intervals of 15 cm and depth of 30 cm. These holes are filled with the chemical emulsion at the rate of 5 litres per metre length of the wall.

 

Sixth stage: Treatment of other locations. Anti-termite treatment should be made at expansion joints after the subgrade has been laid at 2 litres per linear metre of expansion joint. Similarly, when pipes and conduits enter the building, the soil around them for a distance of 15 cm and a depth of 7.5 cm should be loosened and treated.

 

Seventh stage: Treatment of wood surfaces. It is also a good practice to paint all fresh wood surfaces, such as door and window posts which will be in contact with masonry, with two coats of the chemical in kerosene oil before it is installed in the building.

 

Post-construction Anti-termite Treatment of Building Foundation

For post-construction operation, a pressure pump will be required for proper penetration of chemicals into the surface to be treated. Proper checks should also be made regarding the adequacy of the number of chemicals (chemicals mixed with water) pumped in. The following procedure is usually adopted:

Treatment of foundation of outside walls around the building. If there is no apron, we make trenches 50 cm deep and equal to the width of a shovel, exposing the foundation near the external walls. Holes 15 cm apart and 50 cm deep are made by an iron rod. Emulsion at the rate of 5 litres per square metre of the vertical surface of the substructure is to be used for each side of the floor. One-half of the quantity is pumped through the holes and the other half is poured along the trench. If there is a concrete apron, 12 mm diameter holes are dug as close to the wall as possible about 30 cm apart and the chemical is pumped into these holes at the rate of 5 litres per linear metre. A similar treatment is to be made for column and plinth beams.

Treatment of soil under floors. For this purpose, 12 mm diameter holes 30 cm apart are made deep enough to reach the soil below along the junctions of wall and floor, along cracks in the floor and along the construction joints. The emulsion with water is pumped into these holes to soak the soil or at the rate of one litre per hole. The holes are then sealed with cement mortar 1:2. (The floor may also be drilled and the ground below treated but this is a cumbersome process.)

Treatment of masonry at plinth level. The movement of termites through the walls can be stopped by drilling holes in the masonry at plinth level at an angle of 45° on both sides of the wall (and especially where wood such as door post is present) at 30 cm centres. The emulsion is pumped till the masonry is soaked or at a maximum of one litre per hole. The holes are then sealed with 1:2 cement mortar.

 

Post-construction Treatment of Woodwork

In post-construction, we may have to deal with buildings in which the woodwork such as doors or fittings (such as shelves) have been attacked by termites

It is better to treat woodwork with the chemical mixed in kerosene oil. Through this process, we get better penetration of the chemical into the wood. First, the masonry around the wood is treated with the chemical and secondly the wood itself is treated by drilling 6 mm diameter holes at 15 cm intervals and infusing it with the kerosene-based chemical. Two coats of the chemical can also be applied to the surface of the wood before applying the paint.

Must read: Anti-Termite Treatments For Types Of Construction Works

FAQ

Which chemical is used in anti-termite treatment?

1.   Chloropyrifos concentrate 1.0% by weight

2.   Heptachlor concentrate 0.5% by weight

3.   Chlordane concentrate 1.0% by weight